On 11/26/2014, 09:56 PM, Chris J Arges wrote: > From: Paolo Bonzini <[email protected]> > > On x86_64, kernel text mappings are mapped read-only with CONFIG_DEBUG_RODATA. > In that case, KVM will fail to patch VMCALL instructions to VMMCALL > as required on AMD processors. > > The failure mode is currently a divide-by-zero exception, which obviously > is a KVM bug that has to be fixed. However, picking the right instruction > between VMCALL and VMMCALL will be faster and will help if you cannot upgrade > the hypervisor.
Now applied to 3.12. Thanks. > Reported-by: Chris Webb <[email protected]> > Tested-by: Chris Webb <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: "H. Peter Anvin" <[email protected]> > Cc: [email protected] > Acked-by: Borislav Petkov <[email protected]> > Signed-off-by: Paolo Bonzini <[email protected]> > (cherry picked from commit c1118b3602c2329671ad5ec8bdf8e374323d6343) > Signed-off-by: Chris J Arges <[email protected]> > > Conflicts: > arch/x86/include/asm/cpufeature.h > --- > arch/x86/include/asm/cpufeature.h | 1 + > arch/x86/include/asm/kvm_para.h | 10 ++++++++-- > arch/x86/kernel/cpu/amd.c | 7 +++++++ > 3 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/include/asm/cpufeature.h > b/arch/x86/include/asm/cpufeature.h > index 89270b4..c2f19a8 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -203,6 +203,7 @@ > #define X86_FEATURE_DECODEASSISTS (8*32+12) /* AMD Decode Assists support */ > #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 */ > > > /* Intel-defined CPU features, CPUID level 0x00000007:0 (ebx), word 9 */ > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h > index c7678e4..e62cf89 100644 > --- a/arch/x86/include/asm/kvm_para.h > +++ b/arch/x86/include/asm/kvm_para.h > @@ -2,6 +2,7 @@ > #define _ASM_X86_KVM_PARA_H > > #include <asm/processor.h> > +#include <asm/alternative.h> > #include <uapi/asm/kvm_para.h> > > extern void kvmclock_init(void); > @@ -16,10 +17,15 @@ static inline bool kvm_check_and_clear_guest_paused(void) > } > #endif /* CONFIG_KVM_GUEST */ > > -/* This instruction is vmcall. On non-VT architectures, it will generate a > - * trap that we will then rewrite to the appropriate instruction. > +#ifdef CONFIG_DEBUG_RODATA > +#define KVM_HYPERCALL \ > + ALTERNATIVE(".byte 0x0f,0x01,0xc1", ".byte 0x0f,0x01,0xd9", > X86_FEATURE_VMMCALL) > +#else > +/* On AMD processors, vmcall will generate a trap that we will > + * then rewrite to the appropriate instruction. > */ > #define KVM_HYPERCALL ".byte 0x0f,0x01,0xc1" > +#endif > > /* For KVM hypercalls, a three-byte sequence of either the vmcall or the > vmmcall > * instruction. The hypervisor may replace it with something else but only > the > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c > index 28233b9..ee51e67 100644 > --- a/arch/x86/kernel/cpu/amd.c > +++ b/arch/x86/kernel/cpu/amd.c > @@ -509,6 +509,13 @@ static void early_init_amd(struct cpuinfo_x86 *c) > } > #endif > > + /* > + * This is only needed to tell the kernel whether to use VMCALL > + * and VMMCALL. VMMCALL is never executed except under virt, so > + * we can set it unconditionally. > + */ > + set_cpu_cap(c, X86_FEATURE_VMMCALL); > + > /* F16h erratum 793, CVE-2013-6885 */ > if (c->x86 == 0x16 && c->x86_model <= 0xf) { > u64 val; > -- js suse labs -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
