paravirt clock source patches, next round. There is now a pvclock-abi.h file with the structs and some longish comments in it and everybody is switched over to use the stuff in there. cheers, Gerd
Gerd Hoffmann
2008-Jun-03 13:07 UTC
[PATCH 1/5] Add structs and functions for paravirt clocksource.
This patch adds structs for the paravirt clocksource ABI
used by both xen and kvm (pvclock-abi.h).
It also adds some helper functions to read system time and
wall clock time from a paravirtual clocksource (pvclock.[ch]).
They are based on the xen code. They are enabled using
CONFIG_PARAVIRT_CLOCK.
Subsequent patches of this series will put the code in use.
Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
---
arch/x86/Kconfig | 4 +
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/pvclock.c | 141 +++++++++++++++++++++++++++++++++++++++++
include/asm-x86/pvclock-abi.h | 42 ++++++++++++
include/asm-x86/pvclock.h | 13 ++++
5 files changed, 201 insertions(+), 0 deletions(-)
create mode 100644 arch/x86/kernel/pvclock.c
create mode 100644 include/asm-x86/pvclock-abi.h
create mode 100644 include/asm-x86/pvclock.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index dcbec34..5fc46c1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -410,6 +410,10 @@ config PARAVIRT
over full virtualization. However, when run without a hypervisor
the kernel is theoretically slower and slightly larger.
+config PARAVIRT_CLOCK
+ bool
+ default n
+
endif
config MEMTEST_BOOTPARAM
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 5e618c3..77807d4 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_VMI) += vmi_32.o vmiclock_32.o
obj-$(CONFIG_KVM_GUEST) += kvm.o
obj-$(CONFIG_KVM_CLOCK) += kvmclock.o
obj-$(CONFIG_PARAVIRT) += paravirt.o paravirt_patch_$(BITS).o
+obj-$(CONFIG_PARAVIRT_CLOCK) += pvclock.o
obj-$(CONFIG_PCSPKR_PLATFORM) += pcspeaker.o
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
new file mode 100644
index 0000000..05fbe9a
--- /dev/null
+++ b/arch/x86/kernel/pvclock.c
@@ -0,0 +1,141 @@
+/* paravirtual clock -- common code used by kvm/xen
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#include <linux/kernel.h>
+#include <linux/percpu.h>
+#include <asm/pvclock.h>
+
+/*
+ * These are perodically updated
+ * xen: magic shared_info page
+ * kvm: gpa registered via msr
+ * and then copied here.
+ */
+struct pvclock_shadow_time {
+ u64 tsc_timestamp; /* TSC at last update of time vals. */
+ u64 system_timestamp; /* Time, in nanosecs, since boot. */
+ u32 tsc_to_nsec_mul;
+ int tsc_shift;
+ u32 version;
+};
+
+/*
+ * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
+ * yielding a 64-bit result.
+ */
+static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
+{
+ u64 product;
+#ifdef __i386__
+ u32 tmp1, tmp2;
+#endif
+
+ if (shift < 0)
+ delta >>= -shift;
+ else
+ delta <<= shift;
+
+#ifdef __i386__
+ __asm__ (
+ "mul %5 ; "
+ "mov %4,%%eax ; "
+ "mov %%edx,%4 ; "
+ "mul %5 ; "
+ "xor %5,%5 ; "
+ "add %4,%%eax ; "
+ "adc %5,%%edx ; "
+ : "=A" (product), "=r" (tmp1), "=r" (tmp2)
+ : "a" ((u32)delta), "1" ((u32)(delta >> 32)),
"2" (mul_frac) );
+#elif __x86_64__
+ __asm__ (
+ "mul %%rdx ; shrd $32,%%rdx,%%rax"
+ : "=a" (product) : "0" (delta), "d"
((u64)mul_frac) );
+#else
+#error implement me!
+#endif
+
+ return product;
+}
+
+static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
+{
+ u64 delta = native_read_tsc() - shadow->tsc_timestamp;
+ return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
+}
+
+/*
+ * Reads a consistent set of time-base values from hypervisor,
+ * into a shadow data area.
+ */
+static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst,
+ struct pvclock_vcpu_time_info *src)
+{
+ do {
+ dst->version = src->version;
+ rmb(); /* fetch version before data */
+ dst->tsc_timestamp = src->tsc_timestamp;
+ dst->system_timestamp = src->system_time;
+ dst->tsc_to_nsec_mul = src->tsc_to_system_mul;
+ dst->tsc_shift = src->tsc_shift;
+ rmb(); /* test version after fetching data */
+ } while ((src->version & 1) || (dst->version != src->version));
+
+ return dst->version;
+}
+
+cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
+{
+ struct pvclock_shadow_time shadow;
+ unsigned version;
+ cycle_t ret, offset;
+
+ do {
+ version = pvclock_get_time_values(&shadow, src);
+ barrier();
+ offset = pvclock_get_nsec_offset(&shadow);
+ ret = shadow.system_timestamp + offset;
+ barrier();
+ } while (version != src->version);
+
+ return ret;
+}
+
+void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
+ struct pvclock_vcpu_time_info *vcpu_time,
+ struct timespec *ts)
+{
+ u32 version;
+ u64 delta;
+ struct timespec now;
+
+ /* get wallclock at system boot */
+ do {
+ version = wall_clock->version;
+ rmb(); /* fetch version before time */
+ now.tv_sec = wall_clock->sec;
+ now.tv_nsec = wall_clock->nsec;
+ rmb(); /* fetch time before checking version */
+ } while ((wall_clock->version & 1) || (version !=
wall_clock->version));
+
+ delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
+ delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
+
+ now.tv_nsec = do_div(delta, NSEC_PER_SEC);
+ now.tv_sec = delta;
+
+ set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
+}
diff --git a/include/asm-x86/pvclock-abi.h b/include/asm-x86/pvclock-abi.h
new file mode 100644
index 0000000..2adb0da
--- /dev/null
+++ b/include/asm-x86/pvclock-abi.h
@@ -0,0 +1,42 @@
+#ifndef _ASM_X86_PVCLOCK_ABI_H_
+#define _ASM_X86_PVCLOCK_ABI_H_
+#ifndef __ASSEMBLY__
+
+/*
+ * These structs MUST NOT be changed.
+ * They are the ABI between hypervisor and guest OS.
+ * Both Xen and KVM are using this.
+ *
+ * pvclock_vcpu_time_info holds the system time and the tsc timestamp
+ * of the last update. So the guest can use the tsc delta to get a
+ * more precise system time.
+ *
+ * pvclock_wall_clock references the point in time when the system
+ * time was zero (usually boot time), thus the guest calculates the
+ * current wall clock by adding the system time.
+ *
+ * Protocol for the "version" fields is: hypervisor raises it (making
+ * it uneven) before it starts updating the fields and raises it again
+ * (making it even) when it is done. Thus the guest can make sure the
+ * time values it got are consistent by checking the version before
+ * and after reading them.
+ */
+
+struct pvclock_vcpu_time_info {
+ uint32_t version;
+ uint32_t pad0;
+ uint64_t tsc_timestamp;
+ uint64_t system_time;
+ uint32_t tsc_to_system_mul;
+ int8_t tsc_shift;
+ int8_t pad[3];
+} __attribute__((__packed__)); /* 32 bytes */
+
+struct pvclock_wall_clock {
+ uint32_t version;
+ uint32_t sec;
+ uint32_t nsec;
+} __attribute__((__packed__));
+
+#endif /* __ASSEMBLY__ */
+#endif /* _ASM_X86_PVCLOCK_ABI_H_ */
diff --git a/include/asm-x86/pvclock.h b/include/asm-x86/pvclock.h
new file mode 100644
index 0000000..85b1bba
--- /dev/null
+++ b/include/asm-x86/pvclock.h
@@ -0,0 +1,13 @@
+#ifndef _ASM_X86_PVCLOCK_H_
+#define _ASM_X86_PVCLOCK_H_
+
+#include <linux/clocksource.h>
+#include <asm/pvclock-abi.h>
+
+/* some helper functions for xen and kvm pv clock sources */
+cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
+void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
+ struct pvclock_vcpu_time_info *vcpu,
+ struct timespec *ts);
+
+#endif /* _ASM_X86_PVCLOCK_H_ */
--
1.5.4.1
Gerd Hoffmann
2008-Jun-03 13:07 UTC
[PATCH 2/5] Make xen use the paravirt clocksource structs and functions.
This patch updates the xen guest to use the pvclock structs
and helper functions.
Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
---
arch/x86/xen/Kconfig | 1 +
arch/x86/xen/time.c | 130 ++++---------------------------------------
include/xen/interface/xen.h | 5 +-
3 files changed, 14 insertions(+), 122 deletions(-)
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index 2e641be..3a4f16a 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -5,6 +5,7 @@
config XEN
bool "Xen guest support"
select PARAVIRT
+ select PARAVIRT_CLOCK
depends on X86_32
depends on X86_CMPXCHG && X86_TSC && !(X86_VISWS ||
X86_VOYAGER)
help
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index c39e1a5..bf31fb5 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -13,6 +13,7 @@
#include <linux/clockchips.h>
#include <linux/kernel_stat.h>
+#include <asm/pvclock.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
@@ -30,17 +31,6 @@
static cycle_t xen_clocksource_read(void);
-/* These are perodically updated in shared_info, and then copied here. */
-struct shadow_time_info {
- u64 tsc_timestamp; /* TSC at last update of time vals. */
- u64 system_timestamp; /* Time, in nanosecs, since boot. */
- u32 tsc_to_nsec_mul;
- int tsc_shift;
- u32 version;
-};
-
-static DEFINE_PER_CPU(struct shadow_time_info, shadow_time);
-
/* runstate info updated by Xen */
static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate);
@@ -230,121 +220,26 @@ unsigned long xen_cpu_khz(void)
return xen_khz;
}
-/*
- * Reads a consistent set of time-base values from Xen, into a shadow data
- * area.
- */
-static unsigned get_time_values_from_xen(void)
-{
- struct vcpu_time_info *src;
- struct shadow_time_info *dst;
-
- /* src is shared memory with the hypervisor, so we need to
- make sure we get a consistent snapshot, even in the face of
- being preempted. */
- src = &__get_cpu_var(xen_vcpu)->time;
- dst = &__get_cpu_var(shadow_time);
-
- do {
- dst->version = src->version;
- rmb(); /* fetch version before data */
- dst->tsc_timestamp = src->tsc_timestamp;
- dst->system_timestamp = src->system_time;
- dst->tsc_to_nsec_mul = src->tsc_to_system_mul;
- dst->tsc_shift = src->tsc_shift;
- rmb(); /* test version after fetching data */
- } while ((src->version & 1) | (dst->version ^ src->version));
-
- return dst->version;
-}
-
-/*
- * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
- * yielding a 64-bit result.
- */
-static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
-{
- u64 product;
-#ifdef __i386__
- u32 tmp1, tmp2;
-#endif
-
- if (shift < 0)
- delta >>= -shift;
- else
- delta <<= shift;
-
-#ifdef __i386__
- __asm__ (
- "mul %5 ; "
- "mov %4,%%eax ; "
- "mov %%edx,%4 ; "
- "mul %5 ; "
- "xor %5,%5 ; "
- "add %4,%%eax ; "
- "adc %5,%%edx ; "
- : "=A" (product), "=r" (tmp1), "=r" (tmp2)
- : "a" ((u32)delta), "1" ((u32)(delta >> 32)),
"2" (mul_frac) );
-#elif __x86_64__
- __asm__ (
- "mul %%rdx ; shrd $32,%%rdx,%%rax"
- : "=a" (product) : "0" (delta), "d"
((u64)mul_frac) );
-#else
-#error implement me!
-#endif
-
- return product;
-}
-
-static u64 get_nsec_offset(struct shadow_time_info *shadow)
-{
- u64 now, delta;
- now = native_read_tsc();
- delta = now - shadow->tsc_timestamp;
- return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
-}
-
static cycle_t xen_clocksource_read(void)
{
- struct shadow_time_info *shadow = &get_cpu_var(shadow_time);
+ struct vcpu_time_info *src;
cycle_t ret;
- unsigned version;
-
- do {
- version = get_time_values_from_xen();
- barrier();
- ret = shadow->system_timestamp + get_nsec_offset(shadow);
- barrier();
- } while (version != __get_cpu_var(xen_vcpu)->time.version);
-
- put_cpu_var(shadow_time);
+ src = &get_cpu_var(xen_vcpu)->time;
+ ret = pvclock_clocksource_read((void*)src);
+ put_cpu_var(xen_vcpu);
return ret;
}
static void xen_read_wallclock(struct timespec *ts)
{
- const struct shared_info *s = HYPERVISOR_shared_info;
- u32 version;
- u64 delta;
- struct timespec now;
-
- /* get wallclock at system boot */
- do {
- version = s->wc_version;
- rmb(); /* fetch version before time */
- now.tv_sec = s->wc_sec;
- now.tv_nsec = s->wc_nsec;
- rmb(); /* fetch time before checking version */
- } while ((s->wc_version & 1) | (version ^ s->wc_version));
+ struct shared_info *s = HYPERVISOR_shared_info;
+ struct pvclock_wall_clock *wall_clock = &(s->wc);
+ struct vcpu_time_info *vcpu_time;
- delta = xen_clocksource_read(); /* time since system boot */
- delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
-
- now.tv_nsec = do_div(delta, NSEC_PER_SEC);
- now.tv_sec = delta;
-
- set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
+ vcpu_time = &get_cpu_var(xen_vcpu)->time;
+ pvclock_read_wallclock(wall_clock, (void*)vcpu_time, ts);
+ put_cpu_var(xen_vcpu);
}
unsigned long xen_get_wallclock(void)
@@ -352,7 +247,6 @@ unsigned long xen_get_wallclock(void)
struct timespec ts;
xen_read_wallclock(&ts);
-
return ts.tv_sec;
}
@@ -576,8 +470,6 @@ __init void xen_time_init(void)
{
int cpu = smp_processor_id();
- get_time_values_from_xen();
-
clocksource_register(&xen_clocksource);
if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
index 9b018da..aeee096 100644
--- a/include/xen/interface/xen.h
+++ b/include/xen/interface/xen.h
@@ -10,6 +10,7 @@
#define __XEN_PUBLIC_XEN_H__
#include <asm/xen/interface.h>
+#include <asm/pvclock-abi.h>
/*
* XEN "SYSTEM CALLS" (a.k.a. HYPERCALLS).
@@ -384,9 +385,7 @@ struct shared_info {
* Wallclock time: updated only by control software. Guests should base
* their gettimeofday() syscall on this wallclock-base value.
*/
- uint32_t wc_version; /* Version counter: see vcpu_time_info_t. */
- uint32_t wc_sec; /* Secs 00:00:00 UTC, Jan 1, 1970. */
- uint32_t wc_nsec; /* Nsecs 00:00:00 UTC, Jan 1, 1970. */
+ struct pvclock_wall_clock wc;
struct arch_shared_info arch;
--
1.5.4.1
Gerd Hoffmann
2008-Jun-03 13:07 UTC
[PATCH 3/5] Make kvm host use the paravirt clocksource structs.
This patch updates the kvm host code to use the pvclock structs.
It also makes the paravirt clock compatible with Xen.
Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
---
arch/x86/kvm/x86.c | 75 ++++++++++++++++++++++++++++++++++++-------
include/asm-x86/kvm_host.h | 4 ++-
2 files changed, 65 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 77fb2bd..7a62860 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -499,8 +499,8 @@ static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index,
u64 *data)
static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
{
static int version;
- struct kvm_wall_clock wc;
- struct timespec wc_ts;
+ struct pvclock_wall_clock wc;
+ struct timespec now, sys, boot;
if (!wall_clock)
return;
@@ -509,10 +509,19 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t
wall_clock)
kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
- wc_ts = current_kernel_time();
- wc.wc_sec = wc_ts.tv_sec;
- wc.wc_nsec = wc_ts.tv_nsec;
- wc.wc_version = version;
+ /*
+ * The guest calculates current wall clock time by adding
+ * system time (updated by kvm_write_guest_time below) to the
+ * wall clock specified here. guest system time equals host
+ * system time for us, thus we must fill in host boot time here.
+ */
+ now = current_kernel_time();
+ ktime_get_ts(&sys);
+ boot = ns_to_timespec(timespec_to_ns(&now) - timespec_to_ns(&sys));
+
+ wc.sec = boot.tv_sec;
+ wc.nsec = boot.tv_nsec;
+ wc.version = version;
kvm_write_guest(kvm, wall_clock, &wc, sizeof(wc));
@@ -520,6 +529,45 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t
wall_clock)
kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
}
+static uint32_t div_frac(uint32_t dividend, uint32_t divisor)
+{
+ uint32_t quotient, remainder;
+
+ /* Don't try to replace with do_div(), this one calculates
+ * "(dividend << 32) / divisor" */
+ __asm__ ( "divl %4"
+ : "=a" (quotient), "=d" (remainder)
+ : "0" (0), "1" (dividend), "r" (divisor) );
+ return quotient;
+}
+
+static void kvm_set_time_scale(uint32_t tsc_khz, struct pvclock_vcpu_time_info
*hv_clock)
+{
+ uint64_t nsecs = 1000000000LL;
+ int32_t shift = 0;
+ uint64_t tps64;
+ uint32_t tps32;
+
+ tps64 = tsc_khz * 1000LL;
+ while (tps64 > nsecs*2) {
+ tps64 >>= 1;
+ shift--;
+ }
+
+ tps32 = (uint32_t)tps64;
+ while (tps32 <= (uint32_t)nsecs) {
+ tps32 <<= 1;
+ shift++;
+ }
+
+ hv_clock->tsc_shift = shift;
+ hv_clock->tsc_to_system_mul = div_frac(nsecs, tps32);
+
+ pr_debug("%s: tsc_khz %u, tsc_shift %d, tsc_mul %u\n",
+ __FUNCTION__, tsc_khz, hv_clock->tsc_shift,
+ hv_clock->tsc_to_system_mul);
+}
+
static void kvm_write_guest_time(struct kvm_vcpu *v)
{
struct timespec ts;
@@ -530,6 +578,11 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
if ((!vcpu->time_page))
return;
+ if (unlikely(vcpu->hv_clock_tsc_khz != tsc_khz)) {
+ kvm_set_time_scale(tsc_khz, &vcpu->hv_clock);
+ vcpu->hv_clock_tsc_khz = tsc_khz;
+ }
+
/* Keep irq disabled to prevent changes to the clock */
local_irq_save(flags);
kvm_get_msr(v, MSR_IA32_TIME_STAMP_COUNTER,
@@ -544,14 +597,14 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
/*
* The interface expects us to write an even number signaling that the
* update is finished. Since the guest won't see the intermediate
- * state, we just write "2" at the end
+ * state, we just increase by 2 at the end.
*/
- vcpu->hv_clock.version = 2;
+ vcpu->hv_clock.version += 2;
shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);
memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
- sizeof(vcpu->hv_clock));
+ sizeof(vcpu->hv_clock));
kunmap_atomic(shared_kaddr, KM_USER0);
@@ -639,10 +692,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64
data)
/* ...but clean it before doing the actual write */
vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);
- vcpu->arch.hv_clock.tsc_to_system_mul - clocksource_khz2mult(tsc_khz,
22);
- vcpu->arch.hv_clock.tsc_shift = 22;
-
down_read(¤t->mm->mmap_sem);
vcpu->arch.time_page gfn_to_page(vcpu->kvm, data >>
PAGE_SHIFT);
diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h
index cd50380..459461c 100644
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -18,6 +18,7 @@
#include <linux/kvm_para.h>
#include <linux/kvm_types.h>
+#include <asm/pvclock-abi.h>
#include <asm/desc.h>
#define KVM_MAX_VCPUS 16
@@ -285,7 +286,8 @@ struct kvm_vcpu_arch {
struct x86_emulate_ctxt emulate_ctxt;
gpa_t time;
- struct kvm_vcpu_time_info hv_clock;
+ struct pvclock_vcpu_time_info hv_clock;
+ unsigned int hv_clock_tsc_khz;
unsigned int time_offset;
struct page *time_page;
--
1.5.4.1
Gerd Hoffmann
2008-Jun-03 13:07 UTC
[PATCH 4/5] Make kvm guest use the paravirt clocksource structs and functions.
This patch updates the kvm host code to use the pvclock structs
and functions, thereby making it compatible with Xen.
The patch also fixes an initialization bug: on SMP systems the
per-cpu has two different locations early at boot and after CPU
bringup. kvmclock must take that in account when registering the
physical address within the host.
Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
---
arch/x86/Kconfig | 1 +
arch/x86/kernel/kvmclock.c | 91 ++++++++++++++++---------------------------
2 files changed, 35 insertions(+), 57 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5fc46c1..b631288 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -383,6 +383,7 @@ config VMI
config KVM_CLOCK
bool "KVM paravirtualized clock"
select PARAVIRT
+ select PARAVIRT_CLOCK
depends on !(X86_VISWS || X86_VOYAGER)
help
Turning on this option will allow you to run a paravirtualized clock
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 08a3098..927f0c5 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -18,6 +18,7 @@
#include <linux/clocksource.h>
#include <linux/kvm_para.h>
+#include <asm/pvclock.h>
#include <asm/arch_hooks.h>
#include <asm/msr.h>
#include <asm/apic.h>
@@ -36,18 +37,9 @@ static int parse_no_kvmclock(char *arg)
early_param("no-kvmclock", parse_no_kvmclock);
/* The hypervisor will put information about time periodically here */
-static DEFINE_PER_CPU_SHARED_ALIGNED(struct kvm_vcpu_time_info, hv_clock);
-#define get_clock(cpu, field) per_cpu(hv_clock, cpu).field
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
+static struct pvclock_wall_clock wall_clock;
-static inline u64 kvm_get_delta(u64 last_tsc)
-{
- int cpu = smp_processor_id();
- u64 delta = native_read_tsc() - last_tsc;
- return (delta * get_clock(cpu, tsc_to_system_mul)) >> KVM_SCALE;
-}
-
-static struct kvm_wall_clock wall_clock;
-static cycle_t kvm_clock_read(void);
/*
* The wallclock is the time of day when we booted. Since then, some time may
* have elapsed since the hypervisor wrote the data. So we try to account for
@@ -55,64 +47,37 @@ static cycle_t kvm_clock_read(void);
*/
static unsigned long kvm_get_wallclock(void)
{
- u32 wc_sec, wc_nsec;
- u64 delta;
+ struct pvclock_vcpu_time_info *vcpu_time;
struct timespec ts;
- int version, nsec;
int low, high;
low = (int)__pa(&wall_clock);
high = ((u64)__pa(&wall_clock) >> 32);
-
- delta = kvm_clock_read();
-
native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
- do {
- version = wall_clock.wc_version;
- rmb();
- wc_sec = wall_clock.wc_sec;
- wc_nsec = wall_clock.wc_nsec;
- rmb();
- } while ((wall_clock.wc_version != version) || (version & 1));
-
- delta = kvm_clock_read() - delta;
- delta += wc_nsec;
- nsec = do_div(delta, NSEC_PER_SEC);
- set_normalized_timespec(&ts, wc_sec + delta, nsec);
- /*
- * Of all mechanisms of time adjustment I've tested, this one
- * was the champion!
- */
- return ts.tv_sec + 1;
+
+ vcpu_time = &get_cpu_var(hv_clock);
+ pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
+ put_cpu_var(hv_clock);
+
+ return ts.tv_sec;
}
static int kvm_set_wallclock(unsigned long now)
{
- return 0;
+ return -1;
}
-/*
- * This is our read_clock function. The host puts an tsc timestamp each time
- * it updates a new time. Without the tsc adjustment, we can have a situation
- * in which a vcpu starts to run earlier (smaller system_time), but probes
- * time later (compared to another vcpu), leading to backwards time
- */
static cycle_t kvm_clock_read(void)
{
- u64 last_tsc, now;
- int cpu;
-
- preempt_disable();
- cpu = smp_processor_id();
-
- last_tsc = get_clock(cpu, tsc_timestamp);
- now = get_clock(cpu, system_time);
+ struct pvclock_vcpu_time_info *src;
+ cycle_t ret;
- now += kvm_get_delta(last_tsc);
- preempt_enable();
-
- return now;
+ src = &get_cpu_var(hv_clock);
+ ret = pvclock_clocksource_read(src);
+ put_cpu_var(hv_clock);
+ return ret;
}
+
static struct clocksource kvm_clock = {
.name = "kvm-clock",
.read = kvm_clock_read,
@@ -123,13 +88,14 @@ static struct clocksource kvm_clock = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
-static int kvm_register_clock(void)
+static int kvm_register_clock(char *txt)
{
int cpu = smp_processor_id();
int low, high;
low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
-
+ printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
+ cpu, high, low, txt);
return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
}
@@ -140,12 +106,20 @@ static void kvm_setup_secondary_clock(void)
* Now that the first cpu already had this clocksource initialized,
* we shouldn't fail.
*/
- WARN_ON(kvm_register_clock());
+ WARN_ON(kvm_register_clock("secondary cpu clock"));
/* ok, done with our trickery, call native */
setup_secondary_APIC_clock();
}
#endif
+#ifdef CONFIG_SMP
+void __init kvm_smp_prepare_boot_cpu(void)
+{
+ WARN_ON(kvm_register_clock("primary cpu clock"));
+ native_smp_prepare_boot_cpu();
+}
+#endif
+
/*
* After the clock is registered, the host will keep writing to the
* registered memory location. If the guest happens to shutdown, this memory
@@ -174,7 +148,7 @@ void __init kvmclock_init(void)
return;
if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
- if (kvm_register_clock())
+ if (kvm_register_clock("boot clock"))
return;
pv_time_ops.get_wallclock = kvm_get_wallclock;
pv_time_ops.set_wallclock = kvm_set_wallclock;
@@ -182,6 +156,9 @@ void __init kvmclock_init(void)
#ifdef CONFIG_X86_LOCAL_APIC
pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
#endif
+#ifdef CONFIG_SMP
+ smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
+#endif
machine_ops.shutdown = kvm_shutdown;
#ifdef CONFIG_KEXEC
machine_ops.crash_shutdown = kvm_crash_shutdown;
--
1.5.4.1
The kvm_* structs are obsoleted by the pvclock_* ones.
Now all users have been switched over and the old structs
can be dropped.
Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
---
include/asm-x86/kvm_para.h | 18 ------------------
1 files changed, 0 insertions(+), 18 deletions(-)
diff --git a/include/asm-x86/kvm_para.h b/include/asm-x86/kvm_para.h
index 5098459..bfd9900 100644
--- a/include/asm-x86/kvm_para.h
+++ b/include/asm-x86/kvm_para.h
@@ -48,24 +48,6 @@ struct kvm_mmu_op_release_pt {
#ifdef __KERNEL__
#include <asm/processor.h>
-/* xen binary-compatible interface. See xen headers for details */
-struct kvm_vcpu_time_info {
- uint32_t version;
- uint32_t pad0;
- uint64_t tsc_timestamp;
- uint64_t system_time;
- uint32_t tsc_to_system_mul;
- int8_t tsc_shift;
- int8_t pad[3];
-} __attribute__((__packed__)); /* 32 bytes */
-
-struct kvm_wall_clock {
- uint32_t wc_version;
- uint32_t wc_sec;
- uint32_t wc_nsec;
-} __attribute__((__packed__));
-
-
extern void kvmclock_init(void);
--
1.5.4.1
You sent these patches to "kvm-owner", ie. the mailing list owner, and not the list itself which would be plain "kvm".
Jeremy Fitzhardinge
2008-Jun-03 13:34 UTC
[PATCH 1/5] Add structs and functions for paravirt clocksource.
Gerd Hoffmann wrote:> +/* > + * These structs MUST NOT be changed. > + * They are the ABI between hypervisor and guest OS. > + * Both Xen and KVM are using this. > + * > + * pvclock_vcpu_time_info holds the system time and the tsc timestamp > + * of the last update. So the guest can use the tsc delta to get a > + * more precise system time. >You should note that these are per-cpu parameters.> + * > + * pvclock_wall_clock references the point in time when the system > + * time was zero (usually boot time), thus the guest calculates the > + * current wall clock by adding the system time. > + * > + * Protocol for the "version" fields is: hypervisor raises it (making > + * it uneven) before it starts updating the fields and raises it again > + * (making it even) when it is done. Thus the guest can make sure the > + * time values it got are consistent by checking the version before > + * and after reading them. > + */ > + > +struct pvclock_vcpu_time_info { > + uint32_t version; >Use the standard u32/u64 I think (or the __u32 forms, maybe).> + uint32_t pad0; > + uint64_t tsc_timestamp; > + uint64_t system_time; > + uint32_t tsc_to_system_mul; > + int8_t tsc_shift; > + int8_t pad[3]; > +} __attribute__((__packed__)); /* 32 bytes */ > + > +struct pvclock_wall_clock { > + uint32_t version; > + uint32_t sec; > + uint32_t nsec; > +} __attribute__((__packed__)); > + > +#endif /* __ASSEMBLY__ */ > +#endif /* _ASM_X86_PVCLOCK_ABI_H_ */ > diff --git a/include/asm-x86/pvclock.h b/include/asm-x86/pvclock.h > new file mode 100644 > index 0000000..85b1bba > --- /dev/null > +++ b/include/asm-x86/pvclock.h > @@ -0,0 +1,13 @@ > +#ifndef _ASM_X86_PVCLOCK_H_ > +#define _ASM_X86_PVCLOCK_H_ > + > +#include <linux/clocksource.h> > +#include <asm/pvclock-abi.h> > + > +/* some helper functions for xen and kvm pv clock sources */ > +cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src); > +void pvclock_read_wallclock(struct pvclock_wall_clock *wall, > + struct pvclock_vcpu_time_info *vcpu, > + struct timespec *ts); > + > +#endif /* _ASM_X86_PVCLOCK_H_ */ >
Gerd Hoffmann wrote:> paravirt clock source patches, next round. > > There is now a pvclock-abi.h file with the structs and some longish > comments in it and everybody is switched over to use the stuff in > there.This all looks pretty good. How do you want this to get into the kernel? J
Jeremy Fitzhardinge wrote:> Gerd Hoffmann wrote: >> paravirt clock source patches, next round. >> >> There is now a pvclock-abi.h file with the structs and some longish >> comments in it and everybody is switched over to use the stuff in >> there. > > This all looks pretty good. How do you want this to get into the kernel? > > J-- http://kraxel.fedorapeople.org/xenner/
Jeremy Fitzhardinge wrote:> Gerd Hoffmann wrote: >> paravirt clock source patches, next round. >> >> There is now a pvclock-abi.h file with the structs and some longish >> comments in it and everybody is switched over to use the stuff in >> there. > > This all looks pretty good. How do you want this to get into the kernel?[ note: fixed up kvm list address: s/-owner// ] Good question. The kvm patches have dependencies on not-yet merged bits, so they have to go through the kvm queue. The first two can also go through Ingos x86 tree I guess. cheers, Gerd -- http://kraxel.fedorapeople.org/xenner/