From: Yang Weijiang <weijiang.yang@intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: pbonzini@redhat.com, rkrcmar@redhat.com, jmattson@google.com,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
mst@redhat.com, yu-cheng.yu@intel.com,
Zhang Yi Z <yi.z.zhang@linux.intel.com>
Subject: Re: [PATCH v3 3/8] KVM:CPUID: Add CPUID support for Guest CET
Date: Thu, 28 Feb 2019 16:28:32 +0800 [thread overview]
Message-ID: <20190228082831.GB12006@local-michael-cet-test.sh.intel.com> (raw)
In-Reply-To: <20190228155939.GD6166@linux.intel.com>
On Thu, Feb 28, 2019 at 07:59:40AM -0800, Sean Christopherson wrote:
> On Mon, Feb 25, 2019 at 09:27:11PM +0800, Yang Weijiang wrote:
> > Guest CET SHSTK and IBT capability are reported via
> > CPUID.(EAX=7, ECX=0):ECX[bit 7] and EDX[bit 20] respectively.
> > Guest user mode and supervisor mode xsaves component size
> > is reported via CPUID.(EAX=0xD, ECX=1):ECX[bit 11] and ECX[bit 12]
> > respectively.
> >
> > Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
> > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> > ---
> > arch/x86/kvm/cpuid.c | 60 +++++++++++++++++++++++++++++++++-----------
> > arch/x86/kvm/x86.h | 4 +++
> > 2 files changed, 50 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index cb1aece25b17..5e05756cc6db 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -65,6 +65,16 @@ u64 kvm_supported_xcr0(void)
> > return xcr0;
> > }
> >
> > +u64 kvm_supported_xss(void)
> > +{
> > + u64 xss;
> > +
> > + rdmsrl(MSR_IA32_XSS, xss);
> > + xss &= KVM_SUPPORTED_XSS;
> > + return xss;
> > +}
> > +EXPORT_SYMBOL(kvm_supported_xss);
> > +
> > #define F(x) bit(X86_FEATURE_##x)
> >
> > /* For scattered features from cpufeatures.h; we currently expose none */
> > @@ -323,6 +333,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> > u32 index, int *nent, int maxnent)
> > {
> > int r;
> > + u32 eax, ebx, ecx, edx;
> > unsigned f_nx = is_efer_nx() ? F(NX) : 0;
> > #ifdef CONFIG_X86_64
> > unsigned f_gbpages = (kvm_x86_ops->get_lpage_level() == PT_PDPE_LEVEL)
> > @@ -503,6 +514,20 @@ 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);
> > +
> > + /*
> > + * Guest OS CET enabling is designed independent to
> > + * host enabling, it only has dependency on Host HW
> > + * capability, if it has, report CET support to
> > + * Guest.
> > + */
> > + cpuid_count(7, 0, &eax, &ebx, &ecx, &edx);
> > + if (ecx & F(SHSTK))
> > + entry->ecx |= F(SHSTK);
> > +
> > + if (edx & F(IBT))
> > + entry->edx |= F(IBT);
>
> There's no need to manually add these flags. They will be automatically
> kept if supported in hardware because your previous patch, 02/08, added
> them to the mask of features that can be exposed to the guest,
> i.e. set them in kvm_cpuid_7_0_e{c,d}x_x86_features.
>
I shared the same thought as you before, but after I took a closer look at the
kernel code, actually, when host CET feature is disabled by user via
cmdline options(no_cet_shstk and no_cet_ibt), it'll mask out CET feature bits in
boot_cpu_data.x86_capbility[] array, and cpuid_mask() will make the bits
in previous definition lost, so these lines actually add them back when
host CET is disabled.
please check CET kernel patch here:
https://lkml.org/lkml/2018/11/20/204
> > +
> > } 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 && !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.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
> >
next prev parent reply other threads:[~2019-03-01 1:33 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-25 13:27 [PATCH v3 0/8] This patch-set is to enable Guest CET support Yang Weijiang
2019-02-25 13:27 ` [PATCH v3 1/8] KVM:VMX: Define CET VMCS fields and bits Yang Weijiang
2019-02-26 19:31 ` Jim Mattson
2019-02-26 7:52 ` Yang Weijiang
2019-02-28 15:53 ` Sean Christopherson
2019-02-28 9:51 ` Yang Weijiang
2019-02-25 13:27 ` [PATCH v3 2/8] KVM:CPUID: Define CET CPUID bits and CR4.CET master enable bit Yang Weijiang
2019-02-26 19:48 ` Jim Mattson
2019-02-26 7:57 ` Yang Weijiang
2019-03-01 2:15 ` Xiaoyao Li
2019-02-28 16:04 ` Sean Christopherson
2019-02-28 8:10 ` Yang Weijiang
2019-02-25 13:27 ` [PATCH v3 3/8] KVM:CPUID: Add CPUID support for Guest CET Yang Weijiang
2019-02-28 15:59 ` Sean Christopherson
2019-02-28 8:28 ` Yang Weijiang [this message]
2019-03-01 14:53 ` Sean Christopherson
2019-03-03 9:36 ` Yang Weijiang
2019-03-04 18:28 ` Sean Christopherson
2019-03-04 12:17 ` Yang Weijiang
2019-03-04 18:47 ` Sean Christopherson
2019-03-04 10:01 ` Yang Weijiang
2019-03-04 18:54 ` Sean Christopherson
2019-03-04 10:11 ` Yang Weijiang
2019-03-08 11:32 ` Paolo Bonzini
2019-03-10 12:18 ` Yang Weijiang
2019-02-25 13:27 ` [PATCH v3 4/8] KVM:CPUID: Fix xsaves area size calculation for CPUID.(EAX=0xD,ECX=1) Yang Weijiang
2019-02-25 13:27 ` [PATCH v3 5/8] KVM:VMX: Pass through host CET related MSRs to Guest Yang Weijiang
2019-03-04 18:53 ` Sean Christopherson
2019-03-04 10:07 ` Yang Weijiang
2019-03-05 3:21 ` Sean Christopherson
2019-02-25 13:27 ` [PATCH v3 6/8] KVM:VMX: Load Guest CET via VMCS when CET is enabled in Guest Yang Weijiang
2019-02-28 16:17 ` Sean Christopherson
2019-02-28 8:38 ` Yang Weijiang
2019-03-01 14:58 ` Sean Christopherson
2019-03-03 12:26 ` Yang Weijiang
2019-03-04 18:43 ` Sean Christopherson
2019-03-04 9:56 ` Yang Weijiang
2019-03-05 3:12 ` Sean Christopherson
2019-03-04 12:36 ` Yang Weijiang
2019-03-08 16:28 ` Sean Christopherson
2019-03-08 16:36 ` Paolo Bonzini
2019-02-25 13:27 ` [PATCH v3 7/8] KVM:X86: Add XSS bit 11 and 12 support for CET xsaves/xrstors Yang Weijiang
2019-02-28 16:25 ` Sean Christopherson
2019-02-28 8:44 ` Yang Weijiang
2019-03-08 11:32 ` Paolo Bonzini
2019-03-10 12:20 ` Yang Weijiang
2019-03-10 13:35 ` Yang Weijiang
2019-03-11 15:32 ` Paolo Bonzini
2019-03-12 14:30 ` Yang Weijiang
2019-03-08 10:49 ` Paolo Bonzini
2019-03-11 1:29 ` Kang, Luwei
2019-02-25 13:27 ` [PATCH v3 8/8] KVM:X86: Add user-space read/write interface for CET MSRs Yang Weijiang
2019-02-28 16:32 ` Sean Christopherson
2019-02-28 9:41 ` Yang Weijiang
2019-03-08 17:30 ` Sean Christopherson
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