Rusty Russell
2007-Jul-03 23:19 UTC
[PATCH 1/2] lguest: handle dodgy/non-existent TSC. Host code.
Lguest currently requires a TSC, which breaks older machines and Matt
Mackall who boots the host with "notsc". In addition, there is no
good solution to changing TSC speeds (informing all the guests about
the TSC impending change before it happens would be a great deal of
code and have issues with disobedient guests).
This patch makes the host determine if the TSC is both constant and
stable: if not, it doesn't tell the guest to use it. We export
check_tsc_unstable() for this.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
arch/i386/kernel/tsc.c | 3 ++-
drivers/lguest/core.c | 8 --------
drivers/lguest/hypercalls.c | 9 +++++++++
include/asm-i386/tsc.h | 1 +
4 files changed, 12 insertions(+), 9 deletions(-)
==================================================================---
a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -59,10 +59,11 @@ __setup("notsc", tsc_setup);
*/
static int tsc_unstable;
-static inline int check_tsc_unstable(void)
+int check_tsc_unstable(void)
{
return tsc_unstable;
}
+EXPORT_SYMBOL_GPL(check_tsc_unstable);
unsigned long native_calculate_cpu_khz(void)
{
==================================================================---
a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -332,14 +332,6 @@ int run_guest(struct lguest *lg, unsigne
continue;
}
- /* If the Guest hasn't been told the clock multiplier to use or
- * it's changed, we update it here. */
- if (unlikely(lg->tsc_khz != tsc_khz) && lg->lguest_data) {
- lg->tsc_khz = tsc_khz;
- if (put_user(lg->tsc_khz, &lg->lguest_data->tsc_khz))
- return -EFAULT;
- }
-
local_irq_disable();
/* Even if *we* don't want FPU trap, guest might... */
==================================================================---
a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -132,11 +132,19 @@ static void do_async_hcalls(struct lgues
static void initialize(struct lguest *lg)
{
+ u32 tsc_speed;
+
if (lg->regs->eax != LHCALL_LGUEST_INIT) {
kill_guest(lg, "hypercall %li before LGUEST_INIT",
lg->regs->eax);
return;
}
+
+ /* We only tell the guest to use the TSC if it's reliable. */
+ if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable())
+ tsc_speed = tsc_khz;
+ else
+ tsc_speed = 0;
lg->lguest_data = (struct lguest_data __user *)lg->regs->edx;
/* We check here so we can simply copy_to_user/from_user */
@@ -148,6 +156,7 @@ static void initialize(struct lguest *lg
|| get_user(lg->noirq_end, &lg->lguest_data->noirq_end)
/* We reserve the top pgd entry. */
|| put_user(4U*1024*1024, &lg->lguest_data->reserve_mem)
+ || put_user(tsc_speed, &lg->lguest_data->tsc_khz)
|| put_user(lg->guestid, &lg->lguest_data->guestid))
kill_guest(lg, "bad guest page %p", lg->lguest_data);
==================================================================---
a/include/asm-i386/tsc.h
+++ b/include/asm-i386/tsc.h
@@ -63,6 +63,7 @@ extern void mark_tsc_unstable(char *reas
extern void mark_tsc_unstable(char *reason);
extern int unsynchronized_tsc(void);
extern void init_tsc_clocksource(void);
+int check_tsc_unstable(void);
/*
* Boot-time check whether the TSCs are synchronized across
Rusty Russell
2007-Jul-03 23:20 UTC
[PATCH 2/2] lguest: handle dodgy/non-existent TSC. Guest code.
We create an "lguest_clock" which the guest uses: either TSC or
jiffies, depending on whether the host tells us the TSC frequency.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
drivers/lguest/lguest.c | 51 +++++++++++++++++++++++------------------------
1 file changed, 26 insertions(+), 25 deletions(-)
==================================================================---
a/drivers/lguest/lguest.c
+++ b/drivers/lguest/lguest.c
@@ -212,8 +212,8 @@ static void lguest_cpuid(unsigned int *e
case 1: /* Basic feature request. */
/* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */
*ecx &= 0x00002201;
- /* SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, TSC, FPU. */
- *edx &= 0x07808111;
+ /* SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, FPU. */
+ *edx &= 0x07808101;
/* Host wants to know when we flush kernel pages: set PGE. */
*edx |= 0x00002000;
break;
@@ -348,16 +348,19 @@ static unsigned long lguest_get_wallcloc
return hcall(LHCALL_GET_WALLCLOCK, 0, 0, 0);
}
-/* This is what we tell the kernel is our clocksource. It's the normal
"Time
- * Stamp Counter": the Host tells us what speed it's going at. */
+static cycle_t lguest_clock_read(void)
+{
+ if (lguest_data.tsc_khz)
+ return native_read_tsc();
+ else
+ return jiffies;
+}
+
+/* This is what we tell the kernel is our clocksource. */
static struct clocksource lguest_clock = {
.name = "lguest",
.rating = 400,
- .read = native_read_tsc,
- .mask = CLOCKSOURCE_MASK(64),
- .mult = 0, /* to be set */
- .shift = 22,
- .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+ .read = lguest_clock_read,
};
/* We also need a "struct clock_event_device": Linux asks us to set
it to go
@@ -414,14 +417,6 @@ static void lguest_time_irq(unsigned int
{
unsigned long flags;
- /* Check in case host TSC has changed rate. */
- if (unlikely(tsc_khz != lguest_data.tsc_khz)) {
- tsc_khz = lguest_data.tsc_khz;
- lguest_clock.mult = clocksource_khz2mult(tsc_khz, 22);
- __get_cpu_var(sc_data).cyc2ns_scale
- = (1000000 << CYC2NS_SCALE_FACTOR) / tsc_khz;
- }
-
/* Don't interrupt us while this is running. */
local_irq_save(flags);
lguest_clockevent.event_handler(&lguest_clockevent);
@@ -432,7 +427,20 @@ static void lguest_time_init(void)
{
set_irq_handler(0, lguest_time_irq);
- lguest_clock.mult = clocksource_khz2mult(tsc_khz, 22);
+ /* We use the TSC if the Host tells us we can, otherwise a dumb
+ * jiffies-based clock. */
+ if (lguest_data.tsc_khz) {
+ lguest_clock.shift = 22;
+ lguest_clock.mult = clocksource_khz2mult(lguest_data.tsc_khz,
+ lguest_clock.shift);
+ lguest_clock.mask = CLOCKSOURCE_MASK(64);
+ lguest_clock.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+ } else {
+ /* To understand this, start at kernel/time/jiffies.c... */
+ lguest_clock.shift = 8;
+ lguest_clock.mult = (((u64)NSEC_PER_SEC<<8)/ACTHZ) << 8;
+ lguest_clock.mask = CLOCKSOURCE_MASK(32);
+ }
clocksource_register(&lguest_clock);
/* We can't set cpumask in the initializer: damn C limitations! */
@@ -440,12 +448,6 @@ static void lguest_time_init(void)
clockevents_register_device(&lguest_clockevent);
enable_lguest_irq(0);
-}
-
-static unsigned long lguest_get_cpu_khz(void)
-{
- /* The Host tells us the TSC speed */
- return lguest_data.tsc_khz;
}
static void lguest_load_esp0(struct tss_struct *tss,
@@ -584,7 +586,6 @@ __init void lguest_init(void *boot)
paravirt_ops.time_init = lguest_time_init;
paravirt_ops.set_lazy_mode = lguest_lazy_mode;
paravirt_ops.wbinvd = lguest_wbinvd;
- paravirt_ops.get_cpu_khz = lguest_get_cpu_khz;
hcall(LHCALL_LGUEST_INIT, __pa(&lguest_data), 0, 0);
Matt Mackall
2007-Jul-04 06:20 UTC
[PATCH 1/2] lguest: handle dodgy/non-existent TSC. Host code.
On Wed, Jul 04, 2007 at 04:19:32PM +1000, Rusty Russell wrote:> Lguest currently requires a TSC, which breaks older machines and Matt > Mackall who boots the host with "notsc".I do? I temporarily had a "notsc" arg in my lguest launcher script, but removing it made no difference. I do* boot the host with NO_HZ though. -- Mathematics is the supreme nostalgia of our time.