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Date: Fri, 25 Jan 2019 14:40:15 -0800
From: Sean Christopherson <sean.j.christopherson@...el.com>
To: Yang Weijiang <weijiang.yang@...el.com>
Cc: pbonzini@...hat.com, rkrcmar@...hat.com, jmattson@...gle.com,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org, mst@...hat.com,
yu-cheng.yu@...el.com, yi.z.zhang@...el.com, hjl.tools@...il.com,
Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: Re: [PATCH v2 3/7] KVM:CPUID: Add CPUID support for CET xsaves
component query.
On Wed, Jan 23, 2019 at 04:59:05AM +0800, Yang Weijiang wrote:
> CET xsaves component size is queried through CPUID.(EAX=0xD, ECX=11)
> and CPUID.(EAX=0xD, ECX=12).
>
> Signed-off-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> ---
> arch/x86/kvm/cpuid.c | 60 +++++++++++++++++++++++++++++++++-----------
> arch/x86/kvm/x86.c | 4 +++
> arch/x86/kvm/x86.h | 4 +++
> 3 files changed, 54 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index cb1aece25b17..dbeb4e7904eb 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -27,6 +27,8 @@
> #include "trace.h"
> #include "pmu.h"
>
> +extern u64 host_xss;
Probably better to put this in x86.h next to host_xcr0.
> +
> static u32 xstate_required_size(u64 xstate_bv, bool compacted)
> {
> int feature_bit = 0;
> @@ -65,6 +67,19 @@ u64 kvm_supported_xcr0(void)
> return xcr0;
> }
>
> +u64 kvm_supported_xss(void)
> +{
> + u64 xss = host_xss & KVM_SUPPORTED_XSS;
> +
> + /*
> + * Either SHSTK or IBT feature depends on the xsaves component.
> + */
> + if (!boot_cpu_has(X86_FEATURE_SHSTK) && !boot_cpu_has(X86_FEATURE_IBT))
> + xss &= ~(XFEATURE_MASK_SHSTK_USER | XFEATURE_MASK_SHSTK_KERNEL);
This looks wrong, e.g. the SHSTK bits are allowed for SHSTK=false && IBT=true?
And isn't this redundant, i.e. if the features aren't supported by the
boot cpu then shouldn't the associated bits be cleared in host_xss?
> +
> + return xss;
> +}
> +
> #define F(x) bit(X86_FEATURE_##x)
>
> /* For scattered features from cpufeatures.h; we currently expose none */
> @@ -503,6 +518,16 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> * if the host doesn't support it.
> */
> entry->edx |= F(ARCH_CAPABILITIES);
> + /*
> + * If host doesn't have CET capability,
> + * do not report CET related info.
> + */
> + if (!boot_cpu_has(X86_FEATURE_SHSTK))
> + entry->ecx &= ~F(SHSTK);
> +
> + if (!boot_cpu_has(X86_FEATURE_IBT))
> + entry->edx &= ~F(IBT);
> +
> } else {
> entry->ebx = 0;
> entry->ecx = 0;
> @@ -564,14 +589,17 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> }
> case 0xd: {
> int idx, i;
> - u64 supported = kvm_supported_xcr0();
> + u64 u_supported = kvm_supported_xcr0();
> + u64 s_supported = kvm_supported_xss();
> + u64 supported;
> + int compacted;
>
> - entry->eax &= supported;
> - entry->ebx = xstate_required_size(supported, false);
> + entry->eax &= u_supported;
> + entry->ebx = xstate_required_size(u_supported, false);
> entry->ecx = entry->ebx;
> - entry->edx &= supported >> 32;
> + entry->edx &= u_supported >> 32;
> entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> - if (!supported)
> + if (!u_supported)
Should this be '!u_supported && !s_supported'?
> break;
>
> for (idx = 1, i = 1; idx < 64; ++idx) {
> @@ -583,19 +611,23 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> if (idx == 1) {
> entry[i].eax &= kvm_cpuid_D_1_eax_x86_features;
> cpuid_mask(&entry[i].eax, CPUID_D_1_EAX);
> - entry[i].ebx = 0;
> - if (entry[i].eax & (F(XSAVES)|F(XSAVEC)))
> - entry[i].ebx =
> - xstate_required_size(supported,
> - true);
> + supported = u_supported | s_supported;
> + compacted = entry[i].eax &
> + (F(XSAVES) | F(XSAVEC));
> + entry[i].ebx = xstate_required_size(supported,
> + compacted);
> + entry[i].ecx &= s_supported;
> + entry[i].edx = 0;
> } else {
> + supported = (entry[i].ecx & 1) ? s_supported :
> + u_supported;
> if (entry[i].eax == 0 || !(supported & mask))
> continue;
> - if (WARN_ON_ONCE(entry[i].ecx & 1))
> - continue;
> + entry[i].ecx &= 1;
> + entry[i].edx = 0;
> + if (entry[i].ecx)
> + entry[i].ebx = 0;
> }
> - entry[i].ecx = 0;
> - entry[i].edx = 0;
> entry[i].flags |=
> KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> ++*nent;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a0f8b71b2132..b0ae24913423 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -212,6 +212,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
> };
>
> u64 __read_mostly host_xcr0;
> +u64 __read_mostly host_xss;
>
> static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);
>
> @@ -6838,6 +6839,9 @@ int kvm_arch_init(void *opaque)
> if (boot_cpu_has(X86_FEATURE_XSAVE))
> host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
>
> + if (boot_cpu_has(X86_FEATURE_XSAVES))
> + rdmsrl(MSR_IA32_XSS, host_xss);
> +
> kvm_lapic_init();
> #ifdef CONFIG_X86_64
> pvclock_gtod_register_notifier(&pvclock_gtod_notifier);
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 224cd0a47568..c61da41c3c5c 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -283,6 +283,10 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
> | XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
> | XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
> | XFEATURE_MASK_PKRU)
> +
> +#define KVM_SUPPORTED_XSS (XFEATURE_MASK_SHSTK_USER \
> + | XFEATURE_MASK_SHSTK_KERNEL)
> +
> extern u64 host_xcr0;
>
> extern u64 kvm_supported_xcr0(void);
> --
> 2.17.1
>
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