Messages in this thread Patch in this message | | | Date | Mon, 18 Oct 2021 15:08:35 +0200 | Subject | Re: [PATCH v2 7/7] KVM: VMX: Only context switch some PT MSRs when they exist | From | Paolo Bonzini <> |
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On 27/08/21 09:02, Xiaoyao Li wrote: > The enumeration of Intel PT feature doesn't guarantee the existence of > MSR_IA32_RTIT_OUTPUT_BASE, MSR_IA32_RTIT_OUTPUT_MASK and > MSR_IA32_RTIT_CR3_MATCH. They need to be detected from CPUID 0x14 PT > leaves. > > Detect the existence of them in hardware_setup() and only context switch > them when they exist. Otherwise it will cause #GP when access them.
If intel_pt_validate_hw_cap is not fast enough, it should be optimized. Something like this:
diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 7f406c14715f..9c7167dcb719 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -41,13 +41,15 @@ static struct pt_pmu pt_pmu; * permitted values for certain bit fields). */ #define PT_CAP(_n, _l, _r, _m) \ - [PT_CAP_ ## _n] = { .name = __stringify(_n), .leaf = _l, \ - .reg = _r, .mask = _m } + [PT_CAP_ ## _n] = { .name = __stringify(_n), \ + .index = _l * PT_CPUID_REGS_NUM + _r, \ + .shift = __CONSTANT_FFS_32(_m), \ + .mask = _m } static struct pt_cap_desc { const char *name; - u32 leaf; - u8 reg; + u16 index; + u8 shift; u32 mask; } pt_caps[] = { PT_CAP(max_subleaf, 0, CPUID_EAX, 0xffffffff), @@ -71,10 +73,8 @@ static struct pt_cap_desc { u32 intel_pt_validate_cap(u32 *caps, enum pt_capabilities capability) { struct pt_cap_desc *cd = &pt_caps[capability]; - u32 c = caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg]; - unsigned int shift = __ffs(cd->mask); - return (c & cd->mask) >> shift; + return (caps[cd->index] & cd->mask) >> cd->shift; } EXPORT_SYMBOL_GPL(intel_pt_validate_cap); diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 5e62e2383b7f..b4ee28d91b77 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -211,6 +211,17 @@ static inline int get_count_order_long(unsigned long l) return (int)fls_long(--l); } +#define __CONSTANT_FFS_2(w) \ + (((w) & 1) == 0) +#define __CONSTANT_FFS_4(w) \ + (((w) & 0x3) == 0 ? 2 + __CONSTANT_FFS_2((w) >> 2) : __CONSTANT_FFS_2((w))) +#define __CONSTANT_FFS_8(w) \ + (((w) & 0xf) == 0 ? 4 + __CONSTANT_FFS_4((w) >> 4) : __CONSTANT_FFS_4((w))) +#define __CONSTANT_FFS_16(w) \ + (((w) & 0xff) == 0 ? 8 + __CONSTANT_FFS_8((w) >> 8) : __CONSTANT_FFS_8((w))) +#define __CONSTANT_FFS_32(w) \ + (((w) & 0xffff) == 0 ? 16 + __CONSTANT_FFS_16((w) >> 16) : __CONSTANT_FFS_16((w))) + /** * __ffs64 - find first set bit in a 64 bit word * @word: The 64 bit word
Paolo
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> > --- > arch/x86/kvm/vmx/vmx.c | 28 +++++++++++++++++++++------- > 1 file changed, 21 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 394ef4732838..6819fc470072 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -204,6 +204,9 @@ module_param(ple_window_max, uint, 0444); > int __read_mostly pt_mode = PT_MODE_SYSTEM; > module_param(pt_mode, int, S_IRUGO); > > +static bool has_msr_rtit_cr3_match; > +static bool has_msr_rtit_output_x; > + > static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush); > static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond); > static DEFINE_MUTEX(vmx_l1d_flush_mutex); > @@ -1035,9 +1038,12 @@ static inline void pt_load_msr(struct pt_ctx *ctx, u32 addr_range) > u32 i; > > wrmsrl(MSR_IA32_RTIT_STATUS, ctx->status); > - wrmsrl(MSR_IA32_RTIT_OUTPUT_BASE, ctx->output_base); > - wrmsrl(MSR_IA32_RTIT_OUTPUT_MASK, ctx->output_mask); > - wrmsrl(MSR_IA32_RTIT_CR3_MATCH, ctx->cr3_match); > + if (has_msr_rtit_output_x) { > + wrmsrl(MSR_IA32_RTIT_OUTPUT_BASE, ctx->output_base); > + wrmsrl(MSR_IA32_RTIT_OUTPUT_MASK, ctx->output_mask); > + } > + if (has_msr_rtit_cr3_match) > + wrmsrl(MSR_IA32_RTIT_CR3_MATCH, ctx->cr3_match); > for (i = 0; i < addr_range; i++) { > wrmsrl(MSR_IA32_RTIT_ADDR0_A + i * 2, ctx->addr_a[i]); > wrmsrl(MSR_IA32_RTIT_ADDR0_B + i * 2, ctx->addr_b[i]); > @@ -1049,9 +1055,12 @@ static inline void pt_save_msr(struct pt_ctx *ctx, u32 addr_range) > u32 i; > > rdmsrl(MSR_IA32_RTIT_STATUS, ctx->status); > - rdmsrl(MSR_IA32_RTIT_OUTPUT_BASE, ctx->output_base); > - rdmsrl(MSR_IA32_RTIT_OUTPUT_MASK, ctx->output_mask); > - rdmsrl(MSR_IA32_RTIT_CR3_MATCH, ctx->cr3_match); > + if (has_msr_rtit_output_x) { > + rdmsrl(MSR_IA32_RTIT_OUTPUT_BASE, ctx->output_base); > + rdmsrl(MSR_IA32_RTIT_OUTPUT_MASK, ctx->output_mask); > + } > + if (has_msr_rtit_cr3_match) > + rdmsrl(MSR_IA32_RTIT_CR3_MATCH, ctx->cr3_match); > for (i = 0; i < addr_range; i++) { > rdmsrl(MSR_IA32_RTIT_ADDR0_A + i * 2, ctx->addr_a[i]); > rdmsrl(MSR_IA32_RTIT_ADDR0_B + i * 2, ctx->addr_b[i]); > @@ -7883,8 +7892,13 @@ static __init int hardware_setup(void) > > if (pt_mode != PT_MODE_SYSTEM && pt_mode != PT_MODE_HOST_GUEST) > return -EINVAL; > - if (!enable_ept || !cpu_has_vmx_intel_pt()) > + if (!enable_ept || !cpu_has_vmx_intel_pt()) { > pt_mode = PT_MODE_SYSTEM; > + } else if (boot_cpu_has(X86_FEATURE_INTEL_PT)) { > + has_msr_rtit_cr3_match = intel_pt_validate_hw_cap(PT_CAP_cr3_filtering); > + has_msr_rtit_output_x = intel_pt_validate_hw_cap(PT_CAP_topa_output) || > + intel_pt_validate_hw_cap(PT_CAP_single_range_output); > + } > > setup_default_sgx_lepubkeyhash(); > >
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