lkml.org 
[lkml]   [2020]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v11 2/9] KVM: VMX: Set guest CET MSRs per KVM and host configuration
    On Thu, Apr 23, 2020 at 09:27:49AM -0700, Sean Christopherson wrote:
    > On Thu, Mar 26, 2020 at 04:18:39PM +0800, Yang Weijiang wrote:
    > > @@ -3033,6 +3033,13 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
    > > vmcs_writel(GUEST_CR3, guest_cr3);
    > > }
    > >
    > > +static bool is_cet_mode_allowed(struct kvm_vcpu *vcpu, u32 mode_mask)
    >
    > CET itself isn't a mode. And since this ends up being an inner helper for
    > is_cet_supported(), I think __is_cet_supported() would be the way to go.
    >
    > Even @mode_mask is a bit confusing without the context of it being kernel
    > vs. user. The callers are very readable, e.g. I'd much prefer passing the
    > mask as opposed to doing 'bool kernel'. Maybe s/mode_mask/cet_mask? That
    > doesn't exactly make things super clear, but at least the reader knows the
    > mask is for CET features.
    Make sense, will change it.

    >
    > > +{
    > > + return ((supported_xss & mode_mask) &&
    > > + (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
    > > + guest_cpuid_has(vcpu, X86_FEATURE_IBT)));
    > > +}
    > > +
    > > int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
    > > {
    > > struct vcpu_vmx *vmx = to_vmx(vcpu);
    > > @@ -7064,6 +7071,35 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
    > > vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4));
    > > }
    > >
    > > +static void vmx_update_intercept_for_cet_msr(struct kvm_vcpu *vcpu)
    > > +{
    > > + struct vcpu_vmx *vmx = to_vmx(vcpu);
    > > + unsigned long *msr_bitmap = vmx->vmcs01.msr_bitmap;
    > > + bool flag;
    >
    > Maybe s/flag/incpt or something to make it more obvious that the bool is
    > true if we want to intercept? vmx_set_intercept_for_msr()s's @value isn't
    > any better :-/.
    I prefer using incpt now ;-)
    > > +
    > > + flag = !is_cet_mode_allowed(vcpu, XFEATURE_MASK_CET_USER);
    > > + /*
    > > + * U_CET is required for USER CET, and U_CET, PL3_SPP are bound as
    > > + * one component and controlled by IA32_XSS[bit 11].
    > > + */
    > > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW, flag);
    > > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW, flag);
    > > +
    > > + flag = !is_cet_mode_allowed(vcpu, XFEATURE_MASK_CET_KERNEL);
    > > + /*
    > > + * S_CET is required for KERNEL CET, and PL0_SSP ... PL2_SSP are
    > > + * bound as one component and controlled by IA32_XSS[bit 12].
    > > + */
    > > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW, flag);
    > > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW, flag);
    > > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL1_SSP, MSR_TYPE_RW, flag);
    > > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_PL2_SSP, MSR_TYPE_RW, flag);
    > > +
    > > + flag |= !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK);
    > > + /* SSP_TAB is only available for KERNEL SHSTK.*/
    > > + vmx_set_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW, flag);
    > > +}
    > > +
    > > static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
    > > {
    > > struct vcpu_vmx *vmx = to_vmx(vcpu);
    > > @@ -7102,6 +7138,10 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
    > > vmx_set_guest_msr(vmx, msr, enabled ? 0 : TSX_CTRL_RTM_DISABLE);
    > > }
    > > }
    > > +
    > > + if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
    > > + guest_cpuid_has(vcpu, X86_FEATURE_IBT))
    > > + vmx_update_intercept_for_cet_msr(vcpu);
    >
    > This is wrong, it will miss the case where userspace double configures CPUID
    > and goes from CET=1 to CET=0. This should instead be:
    >
    > if (supported_xss & (XFEATURE_MASK_CET_KERNEL | XFEATURE_MASK_CET_USER))
    > vmx_update_intercept_for_cet_msr(vcpu);
    >
    > > }
    Here CET=1/0, did you mean the CET bit in XSS or CR4.CET? If it's the
    former, then it's OK for me.

    > >
    > > static __init void vmx_set_cpu_caps(void)
    > > --
    > > 2.17.2
    > >

    \
     
     \ /
      Last update: 2020-04-24 16:06    [W:3.286 / U:0.028 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site