The first patch fixes Xen PV regression introduced by 32-bit rewrite. Unlike the earlier version it uses ALTERNATIVE instruction and avoids using xen_sysexit (and sysret32 in compat mode) pv ops, as suggested by Andy. (I ended up patching TEST with XOR to avoid extra NOPs, even though I said yesterday it would be wrong. It's not wrong) As result of this patch irq_enable_sysexit and usergs_sysret32 pv ops are not used anymore by anyone and so can be removed. Boris Ostrovsky (3): x86/xen: Avoid fast syscall path for Xen PV guests x86: irq_enable_sysexit pv op is no longer needed x86: usergs_sysret32 pv op is no longer needed arch/x86/entry/entry_32.S | 11 ++++------- arch/x86/entry/entry_64_compat.S | 16 ++++++---------- arch/x86/include/asm/cpufeature.h | 1 + arch/x86/include/asm/paravirt.h | 12 ------------ arch/x86/include/asm/paravirt_types.h | 17 ----------------- arch/x86/kernel/asm-offsets.c | 3 --- arch/x86/kernel/asm-offsets_64.c | 1 - arch/x86/kernel/paravirt.c | 12 ------------ arch/x86/kernel/paravirt_patch_32.c | 2 -- arch/x86/kernel/paravirt_patch_64.c | 3 --- arch/x86/xen/enlighten.c | 7 +++---- arch/x86/xen/xen-asm_32.S | 14 -------------- arch/x86/xen/xen-asm_64.S | 19 ------------------- arch/x86/xen/xen-ops.h | 3 --- 14 files changed, 14 insertions(+), 107 deletions(-) -- 1.8.1.4
Boris Ostrovsky
2015-Nov-18 20:06 UTC
[PATCH 1/3] x86/xen: Avoid fast syscall path for Xen PV guests
After 32-bit syscall rewrite, and specifically after commit 5f310f739b4c ("x86/entry/32: Re-implement SYSENTER using the new C path"), the stack frame that is passed to xen_sysexit is no longer a "standard" one (i.e. it's not pt_regs). Since we end up calling xen_iret from xen_sysexit we don't need to fix up the stack and instead follow entry_SYSENTER_32's IRET path directly to xen_iret. We can do the same thing for compat mode even though stack does not need to be fixed. This will allow us to drop usergs_sysret32 paravirt op (in the subsequent patch) Signed-off-by: Boris Ostrovsky <boris.ostrovsky at oracle.com> Suggested-by: Andy Lutomirski <luto at amacapital.net> --- arch/x86/entry/entry_32.S | 3 ++- arch/x86/entry/entry_64_compat.S | 6 ++++-- arch/x86/include/asm/cpufeature.h | 1 + arch/x86/xen/enlighten.c | 4 +++- 4 files changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 3eb572e..901f186 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -308,7 +308,8 @@ sysenter_past_esp: movl %esp, %eax call do_fast_syscall_32 - testl %eax, %eax + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax", "xor %eax, %eax", X86_FEATURE_XENPV jz .Lsyscall_32_done /* Opportunistic SYSEXIT */ diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index c320183..98893d9 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -121,7 +121,8 @@ sysenter_flags_fixed: movq %rsp, %rdi call do_fast_syscall_32 - testl %eax, %eax + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax", "xor %eax, %eax", X86_FEATURE_XENPV jz .Lsyscall_32_done jmp sysret32_from_system_call @@ -200,7 +201,8 @@ ENTRY(entry_SYSCALL_compat) movq %rsp, %rdi call do_fast_syscall_32 - testl %eax, %eax + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax", "xor %eax, %eax", X86_FEATURE_XENPV jz .Lsyscall_32_done /* Opportunistic SYSRET */ diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index e4f8010..0e4fe5b 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -216,6 +216,7 @@ #define X86_FEATURE_PAUSEFILTER ( 8*32+13) /* AMD filtered pause intercept */ #define X86_FEATURE_PFTHRESHOLD ( 8*32+14) /* AMD pause filter threshold */ #define X86_FEATURE_VMMCALL ( 8*32+15) /* Prefer vmmcall to vmcall */ +#define X86_FEATURE_XENPV ( 8*32+16) /* Xen paravirtual guest */ /* Intel-defined CPU features, CPUID level 0x00000007:0 (ebx), word 9 */ diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 5774800..d315151 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -1886,8 +1886,10 @@ EXPORT_SYMBOL_GPL(xen_hvm_need_lapic); static void xen_set_cpu_features(struct cpuinfo_x86 *c) { - if (xen_pv_domain()) + if (xen_pv_domain()) { clear_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS); + set_cpu_cap(c, X86_FEATURE_XENPV); + } } const struct hypervisor_x86 x86_hyper_xen = { -- 1.8.1.4
Boris Ostrovsky
2015-Nov-18 20:06 UTC
[PATCH 2/3] x86: irq_enable_sysexit pv op is no longer needed
Xen PV guests have been the only ones using it and now they don't. Signed-off-by: Boris Ostrovsky <boris.ostrovsky at oracle.com> --- arch/x86/entry/entry_32.S | 8 ++------ arch/x86/include/asm/paravirt.h | 7 ------- arch/x86/include/asm/paravirt_types.h | 9 --------- arch/x86/kernel/asm-offsets.c | 3 --- arch/x86/kernel/paravirt.c | 7 ------- arch/x86/kernel/paravirt_patch_32.c | 2 -- arch/x86/kernel/paravirt_patch_64.c | 1 - arch/x86/xen/enlighten.c | 3 --- arch/x86/xen/xen-asm_32.S | 14 -------------- arch/x86/xen/xen-ops.h | 3 --- 10 files changed, 2 insertions(+), 55 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 901f186..e2158ae 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -329,7 +329,8 @@ sysenter_past_esp: * Return back to the vDSO, which will pop ecx and edx. * Don't bother with DS and ES (they already contain __USER_DS). */ - ENABLE_INTERRUPTS_SYSEXIT + sti + sysexit .pushsection .fixup, "ax" 2: movl $0, PT_FS(%esp) @@ -552,11 +553,6 @@ ENTRY(native_iret) iret _ASM_EXTABLE(native_iret, iret_exc) END(native_iret) - -ENTRY(native_irq_enable_sysexit) - sti - sysexit -END(native_irq_enable_sysexit) #endif ENTRY(overflow) diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index 10d0596..c28518e 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -932,13 +932,6 @@ extern void default_banner(void); push %ecx; push %edx; \ call PARA_INDIRECT(pv_cpu_ops+PV_CPU_read_cr0); \ pop %edx; pop %ecx - -#define ENABLE_INTERRUPTS_SYSEXIT \ - PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_irq_enable_sysexit), \ - CLBR_NONE, \ - jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_irq_enable_sysexit)) - - #else /* !CONFIG_X86_32 */ /* diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 31247b5..608bbf3 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -157,15 +157,6 @@ struct pv_cpu_ops { u64 (*read_pmc)(int counter); -#ifdef CONFIG_X86_32 - /* - * Atomically enable interrupts and return to userspace. This - * is only used in 32-bit kernels. 64-bit kernels use - * usergs_sysret32 instead. - */ - void (*irq_enable_sysexit)(void); -#endif - /* * Switch to usermode gs and return to 64-bit usermode using * sysret. Only used in 64-bit kernels to return to 64-bit diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c index 439df97..84a7524 100644 --- a/arch/x86/kernel/asm-offsets.c +++ b/arch/x86/kernel/asm-offsets.c @@ -65,9 +65,6 @@ void common(void) { OFFSET(PV_IRQ_irq_disable, pv_irq_ops, irq_disable); OFFSET(PV_IRQ_irq_enable, pv_irq_ops, irq_enable); OFFSET(PV_CPU_iret, pv_cpu_ops, iret); -#ifdef CONFIG_X86_32 - OFFSET(PV_CPU_irq_enable_sysexit, pv_cpu_ops, irq_enable_sysexit); -#endif OFFSET(PV_CPU_read_cr0, pv_cpu_ops, read_cr0); OFFSET(PV_MMU_read_cr2, pv_mmu_ops, read_cr2); #endif diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index c2130ae..c55f437 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -162,9 +162,6 @@ unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf, ret = paravirt_patch_ident_64(insnbuf, len); else if (type == PARAVIRT_PATCH(pv_cpu_ops.iret) || -#ifdef CONFIG_X86_32 - type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit) || -#endif type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret32) || type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret64)) /* If operation requires a jmp, then jmp */ @@ -220,7 +217,6 @@ static u64 native_steal_clock(int cpu) /* These are in entry.S */ extern void native_iret(void); -extern void native_irq_enable_sysexit(void); extern void native_usergs_sysret32(void); extern void native_usergs_sysret64(void); @@ -379,9 +375,6 @@ __visible struct pv_cpu_ops pv_cpu_ops = { .load_sp0 = native_load_sp0, -#if defined(CONFIG_X86_32) - .irq_enable_sysexit = native_irq_enable_sysexit, -#endif #ifdef CONFIG_X86_64 #ifdef CONFIG_IA32_EMULATION .usergs_sysret32 = native_usergs_sysret32, diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c index c89f50a..158dc06 100644 --- a/arch/x86/kernel/paravirt_patch_32.c +++ b/arch/x86/kernel/paravirt_patch_32.c @@ -5,7 +5,6 @@ DEF_NATIVE(pv_irq_ops, irq_enable, "sti"); DEF_NATIVE(pv_irq_ops, restore_fl, "push %eax; popf"); DEF_NATIVE(pv_irq_ops, save_fl, "pushf; pop %eax"); DEF_NATIVE(pv_cpu_ops, iret, "iret"); -DEF_NATIVE(pv_cpu_ops, irq_enable_sysexit, "sti; sysexit"); DEF_NATIVE(pv_mmu_ops, read_cr2, "mov %cr2, %eax"); DEF_NATIVE(pv_mmu_ops, write_cr3, "mov %eax, %cr3"); DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax"); @@ -46,7 +45,6 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, PATCH_SITE(pv_irq_ops, restore_fl); PATCH_SITE(pv_irq_ops, save_fl); PATCH_SITE(pv_cpu_ops, iret); - PATCH_SITE(pv_cpu_ops, irq_enable_sysexit); PATCH_SITE(pv_mmu_ops, read_cr2); PATCH_SITE(pv_mmu_ops, read_cr3); PATCH_SITE(pv_mmu_ops, write_cr3); diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c index 8aa0558..17c00f8 100644 --- a/arch/x86/kernel/paravirt_patch_64.c +++ b/arch/x86/kernel/paravirt_patch_64.c @@ -13,7 +13,6 @@ DEF_NATIVE(pv_mmu_ops, flush_tlb_single, "invlpg (%rdi)"); DEF_NATIVE(pv_cpu_ops, clts, "clts"); DEF_NATIVE(pv_cpu_ops, wbinvd, "wbinvd"); -DEF_NATIVE(pv_cpu_ops, irq_enable_sysexit, "swapgs; sti; sysexit"); DEF_NATIVE(pv_cpu_ops, usergs_sysret64, "swapgs; sysretq"); DEF_NATIVE(pv_cpu_ops, usergs_sysret32, "swapgs; sysretl"); DEF_NATIVE(pv_cpu_ops, swapgs, "swapgs"); diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index d315151..a068e36 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -1229,10 +1229,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = { .iret = xen_iret, #ifdef CONFIG_X86_64 - .usergs_sysret32 = xen_sysret32, .usergs_sysret64 = xen_sysret64, -#else - .irq_enable_sysexit = xen_sysexit, #endif .load_tr_desc = paravirt_nop, diff --git a/arch/x86/xen/xen-asm_32.S b/arch/x86/xen/xen-asm_32.S index fd92a64..feb6d40 100644 --- a/arch/x86/xen/xen-asm_32.S +++ b/arch/x86/xen/xen-asm_32.S @@ -35,20 +35,6 @@ check_events: ret /* - * We can't use sysexit directly, because we're not running in ring0. - * But we can easily fake it up using iret. Assuming xen_sysexit is - * jumped to with a standard stack frame, we can just strip it back to - * a standard iret frame and use iret. - */ -ENTRY(xen_sysexit) - movl PT_EAX(%esp), %eax /* Shouldn't be necessary? */ - orl $X86_EFLAGS_IF, PT_EFLAGS(%esp) - lea PT_EIP(%esp), %esp - - jmp xen_iret -ENDPROC(xen_sysexit) - -/* * This is run where a normal iret would be run, with the same stack setup: * 8: eflags * 4: cs diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index 1399423..4140b07 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -139,9 +139,6 @@ DECL_ASM(void, xen_restore_fl_direct, unsigned long); /* These are not functions, and cannot be called normally */ __visible void xen_iret(void); -#ifdef CONFIG_X86_32 -__visible void xen_sysexit(void); -#endif __visible void xen_sysret32(void); __visible void xen_sysret64(void); __visible void xen_adjust_exception_frame(void); -- 1.8.1.4
Boris Ostrovsky
2015-Nov-18 20:06 UTC
[PATCH 3/3] x86: usergs_sysret32 pv op is no longer needed
Xen PV guests have been the only ones using it and now they don't. Signed-off-by: Boris Ostrovsky <boris.ostrovsky at oracle.com> --- arch/x86/entry/entry_64_compat.S | 10 ++-------- arch/x86/include/asm/paravirt.h | 5 ----- arch/x86/include/asm/paravirt_types.h | 8 -------- arch/x86/kernel/asm-offsets_64.c | 1 - arch/x86/kernel/paravirt.c | 5 ----- arch/x86/kernel/paravirt_patch_64.c | 2 -- arch/x86/xen/xen-asm_64.S | 19 ------------------- 7 files changed, 2 insertions(+), 48 deletions(-) diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 98893d9..82415dc 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -18,13 +18,6 @@ .section .entry.text, "ax" -#ifdef CONFIG_PARAVIRT -ENTRY(native_usergs_sysret32) - swapgs - sysretl -ENDPROC(native_usergs_sysret32) -#endif - /* * 32-bit SYSENTER instruction entry. * @@ -238,7 +231,8 @@ sysret32_from_system_call: xorq %r9, %r9 xorq %r10, %r10 movq RSP-ORIG_RAX(%rsp), %rsp - USERGS_SYSRET32 + swapgs + sysretl END(entry_SYSCALL_compat) /* diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index c28518e..1b71c3a 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -922,11 +922,6 @@ extern void default_banner(void); call PARA_INDIRECT(pv_irq_ops+PV_IRQ_irq_enable); \ PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);) -#define USERGS_SYSRET32 \ - PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret32), \ - CLBR_NONE, \ - jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usergs_sysret32)) - #ifdef CONFIG_X86_32 #define GET_CR0_INTO_EAX \ push %ecx; push %edx; \ diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 608bbf3..702c8bd 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -165,14 +165,6 @@ struct pv_cpu_ops { */ void (*usergs_sysret64)(void); - /* - * Switch to usermode gs and return to 32-bit usermode using - * sysret. Used to return to 32-on-64 compat processes. - * Other usermode register state, including %esp, must already - * be restored. - */ - void (*usergs_sysret32)(void); - /* Normal iret. Jump to this with the standard iret stack frame set up. */ void (*iret)(void); diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c index d8f42f9..f2edafb 100644 --- a/arch/x86/kernel/asm-offsets_64.c +++ b/arch/x86/kernel/asm-offsets_64.c @@ -23,7 +23,6 @@ int main(void) { #ifdef CONFIG_PARAVIRT OFFSET(PV_IRQ_adjust_exception_frame, pv_irq_ops, adjust_exception_frame); - OFFSET(PV_CPU_usergs_sysret32, pv_cpu_ops, usergs_sysret32); OFFSET(PV_CPU_usergs_sysret64, pv_cpu_ops, usergs_sysret64); OFFSET(PV_CPU_swapgs, pv_cpu_ops, swapgs); BLANK(); diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index c55f437..8c19b4d 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -162,7 +162,6 @@ unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf, ret = paravirt_patch_ident_64(insnbuf, len); else if (type == PARAVIRT_PATCH(pv_cpu_ops.iret) || - type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret32) || type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret64)) /* If operation requires a jmp, then jmp */ ret = paravirt_patch_jmp(insnbuf, opfunc, addr, len); @@ -217,7 +216,6 @@ static u64 native_steal_clock(int cpu) /* These are in entry.S */ extern void native_iret(void); -extern void native_usergs_sysret32(void); extern void native_usergs_sysret64(void); static struct resource reserve_ioports = { @@ -376,9 +374,6 @@ __visible struct pv_cpu_ops pv_cpu_ops = { .load_sp0 = native_load_sp0, #ifdef CONFIG_X86_64 -#ifdef CONFIG_IA32_EMULATION - .usergs_sysret32 = native_usergs_sysret32, -#endif .usergs_sysret64 = native_usergs_sysret64, #endif .iret = native_iret, diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c index 17c00f8..e70087a 100644 --- a/arch/x86/kernel/paravirt_patch_64.c +++ b/arch/x86/kernel/paravirt_patch_64.c @@ -14,7 +14,6 @@ DEF_NATIVE(pv_cpu_ops, clts, "clts"); DEF_NATIVE(pv_cpu_ops, wbinvd, "wbinvd"); DEF_NATIVE(pv_cpu_ops, usergs_sysret64, "swapgs; sysretq"); -DEF_NATIVE(pv_cpu_ops, usergs_sysret32, "swapgs; sysretl"); DEF_NATIVE(pv_cpu_ops, swapgs, "swapgs"); DEF_NATIVE(, mov32, "mov %edi, %eax"); @@ -54,7 +53,6 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, PATCH_SITE(pv_irq_ops, save_fl); PATCH_SITE(pv_irq_ops, irq_enable); PATCH_SITE(pv_irq_ops, irq_disable); - PATCH_SITE(pv_cpu_ops, usergs_sysret32); PATCH_SITE(pv_cpu_ops, usergs_sysret64); PATCH_SITE(pv_cpu_ops, swapgs); PATCH_SITE(pv_mmu_ops, read_cr2); diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S index f22667a..cc8acc4 100644 --- a/arch/x86/xen/xen-asm_64.S +++ b/arch/x86/xen/xen-asm_64.S @@ -68,25 +68,6 @@ ENTRY(xen_sysret64) ENDPATCH(xen_sysret64) RELOC(xen_sysret64, 1b+1) -ENTRY(xen_sysret32) - /* - * We're already on the usermode stack at this point, but - * still with the kernel gs, so we can easily switch back - */ - movq %rsp, PER_CPU_VAR(rsp_scratch) - movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp - - pushq $__USER32_DS - pushq PER_CPU_VAR(rsp_scratch) - pushq %r11 - pushq $__USER32_CS - pushq %rcx - - pushq $0 -1: jmp hypercall_iret -ENDPATCH(xen_sysret32) -RELOC(xen_sysret32, 1b+1) - /* * Xen handles syscall callbacks much like ordinary exceptions, which * means we have: -- 1.8.1.4
Andy Lutomirski
2015-Nov-18 20:21 UTC
[PATCH 1/3] x86/xen: Avoid fast syscall path for Xen PV guests
On Wed, Nov 18, 2015 at 12:06 PM, Boris Ostrovsky <boris.ostrovsky at oracle.com> wrote:> After 32-bit syscall rewrite, and specifically after commit 5f310f739b4c > ("x86/entry/32: Re-implement SYSENTER using the new C path"), the stack > frame that is passed to xen_sysexit is no longer a "standard" one (i.e. > it's not pt_regs). > > Since we end up calling xen_iret from xen_sysexit we don't need to fix > up the stack and instead follow entry_SYSENTER_32's IRET path directly > to xen_iret. > > We can do the same thing for compat mode even though stack does not need > to be fixed. This will allow us to drop usergs_sysret32 paravirt op (in > the subsequent patch)Looks generally quite nice. Minor comments below:> --- a/arch/x86/entry/entry_32.S > +++ b/arch/x86/entry/entry_32.S > @@ -308,7 +308,8 @@ sysenter_past_esp: > > movl %esp, %eax > call do_fast_syscall_32 > - testl %eax, %eax > + /* XEN PV guests always use IRET path */ > + ALTERNATIVE "testl %eax, %eax", "xor %eax, %eax", X86_FEATURE_XENPV > jz .Lsyscall_32_doneCould we make this a little less subtle: ALTERNATIVE "testl %eax, %eax; lz .Lsyscall_32_done", "jmp .Lsyscasll_32_done", X86_FEATURE_XENPV Borislav, what do you think? Ditto for the others.> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h > index e4f8010..0e4fe5b 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -216,6 +216,7 @@ > #define X86_FEATURE_PAUSEFILTER ( 8*32+13) /* AMD filtered pause intercept */ > #define X86_FEATURE_PFTHRESHOLD ( 8*32+14) /* AMD pause filter threshold */ > #define X86_FEATURE_VMMCALL ( 8*32+15) /* Prefer vmmcall to vmcall */ > +#define X86_FEATURE_XENPV ( 8*32+16) /* Xen paravirtual guest */ >This bit is highly magical and I think we need Borislav's ack. --Andy
Andy Lutomirski
2015-Nov-18 20:23 UTC
[PATCH 2/3] x86: irq_enable_sysexit pv op is no longer needed
On Wed, Nov 18, 2015 at 12:06 PM, Boris Ostrovsky <boris.ostrovsky at oracle.com> wrote:> Xen PV guests have been the only ones using it and now they don't.Fantastic! --Andy
Andy Lutomirski
2015-Nov-18 20:26 UTC
[PATCH 3/3] x86: usergs_sysret32 pv op is no longer needed
On Wed, Nov 18, 2015 at 12:06 PM, Boris Ostrovsky <boris.ostrovsky at oracle.com> wrote:> Xen PV guests have been the only ones using it and now they don't.Yay! --Andy
Boris Ostrovsky
2015-Nov-18 20:34 UTC
[PATCH 2/3] x86: irq_enable_sysexit pv op is no longer needed
On 11/18/2015 03:11 PM, Konrad Rzeszutek Wilk wrote:> On Wed, Nov 18, 2015 at 03:06:18PM -0500, Boris Ostrovsky wrote: >> Xen PV guests have been the only ones using it and now they don't. > Could you elaborate on the 'now they don't' please? > > Is Xen not doing it? Did it do it in the past? > > Is it because the Linux code paths will never run to this in Xen PV mode? > Is that due to other patches? If so please mention the name > of the other patches.. (so if somebody is thinking to put the > other patches on the stable train they should also take these ones).Since this is due to the first patch in the series I don't know its commitID. Should I just refer to patch title? -boris
On Wed, Nov 18, 2015 at 03:06:16PM -0500, Boris Ostrovsky wrote:> The first patch fixes Xen PV regression introduced by 32-bit rewrite. Unlike the > earlier version it uses ALTERNATIVE instruction and avoids using xen_sysexit > (and sysret32 in compat mode) pv ops, as suggested by Andy. (I ended up patching > TEST with XOR to avoid extra NOPs, even though I said yesterday it would be > wrong. It's not wrong) > > As result of this patch irq_enable_sysexit and usergs_sysret32 pv ops are not > used anymore by anyone and so can be removed. > > Boris Ostrovsky (3): > x86/xen: Avoid fast syscall path for Xen PV guests > x86: irq_enable_sysexit pv op is no longer needed > x86: usergs_sysret32 pv op is no longer needed > > arch/x86/entry/entry_32.S | 11 ++++------- > arch/x86/entry/entry_64_compat.S | 16 ++++++---------- > arch/x86/include/asm/cpufeature.h | 1 + > arch/x86/include/asm/paravirt.h | 12 ------------ > arch/x86/include/asm/paravirt_types.h | 17 ----------------- > arch/x86/kernel/asm-offsets.c | 3 --- > arch/x86/kernel/asm-offsets_64.c | 1 - > arch/x86/kernel/paravirt.c | 12 ------------ > arch/x86/kernel/paravirt_patch_32.c | 2 -- > arch/x86/kernel/paravirt_patch_64.c | 3 --- > arch/x86/xen/enlighten.c | 7 +++---- > arch/x86/xen/xen-asm_32.S | 14 -------------- > arch/x86/xen/xen-asm_64.S | 19 ------------------- > arch/x86/xen/xen-ops.h | 3 --- > 14 files changed, 14 insertions(+), 107 deletions(-)Can't argue with that diffstat! :-) -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imend?rffer, Jane Smithard, Graham Norton, HRB 21284 (AG N?rnberg) --
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