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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Yang Weijiang <weijiang.yang@intel.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	pbonzini@redhat.com, jmattson@google.com,
	yu.c.zhang@linux.intel.com, yu-cheng.yu@intel.com
Subject: Re: [PATCH v8 4/7] KVM: VMX: Load CET states on vmentry/vmexit
Date: Wed, 11 Dec 2019 08:35:10 -0800	[thread overview]
Message-ID: <20191211163510.GF5044@linux.intel.com> (raw)
In-Reply-To: <20191211015423.GC12845@local-michael-cet-test>

On Wed, Dec 11, 2019 at 09:54:23AM +0800, Yang Weijiang wrote:
> On Tue, Dec 10, 2019 at 01:23:05PM -0800, Sean Christopherson wrote:
> > On Fri, Nov 01, 2019 at 04:52:19PM +0800, Yang Weijiang wrote:
> > > @@ -2834,6 +2837,9 @@ void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
> > >  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> > >  	unsigned long hw_cr0;
> > >  
> > > +	if (!(cr0 & X86_CR0_WP) && kvm_read_cr4_bits(vcpu, X86_CR4_CET))
> > > +		cr0 |= X86_CR0_WP;
> > 
> > Huh?  What's the interaction between CR4.CET and CR0.WP?  If there really
> > is some non-standard interaction then it needs to be documented in at least
> > the changelog and probably with a comment as well.
> >
> The processor does not allow CR4.CET to be set if CR0.WP = 0 (similarly, it
> does not allow CR0.WP to be cleared while CR4.CET = 1).

Ya, as you surmised below, this needs to be a #GP condition.

Have you tested SMM at all?  The interaction between CR0 and CR4 may be
problematic for em_rsm() and/or rsm_enter_protected_mode().

> > > +
> > >  	hw_cr0 = (cr0 & ~KVM_VM_CR0_ALWAYS_OFF);
> > >  	if (enable_unrestricted_guest)
> > >  		hw_cr0 |= KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST;
> > > @@ -2936,6 +2942,22 @@ static bool guest_cet_allowed(struct kvm_vcpu *vcpu, u32 feature, u32 mode)
> > >  	return false;
> > >  }
> > >  
> > > +bool is_cet_bit_allowed(struct kvm_vcpu *vcpu)
> > > +{
> > > +	unsigned long cr0;
> > > +	bool cet_allowed;
> > > +
> > > +	cr0 = kvm_read_cr0(vcpu);
> > > +	cet_allowed = guest_cet_allowed(vcpu, X86_FEATURE_SHSTK,
> > > +					XFEATURE_MASK_CET_USER) ||
> > > +		      guest_cet_allowed(vcpu, X86_FEATURE_IBT,
> > > +					XFEATURE_MASK_CET_USER);
> > > +	if ((cr0 & X86_CR0_WP) && cet_allowed)
> > > +		return true;
> > 
> > So, attempting to set CR4.CET if CR0.WP=0 takes a #GP?  But attempting
> > to clear CR0.WP if CR4.CET=1 is ignored?
> > 
> Per above words in spec., inject #GP to guest in either case?
> 
> > > +
> > > +	return false;
> > > +}
> > > +

  reply	other threads:[~2019-12-11 16:35 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-01  8:52 [PATCH v8 0/7] Introduce support for guest CET feature Yang Weijiang
2019-11-01  8:52 ` [PATCH v8 1/7] KVM: CPUID: Fix IA32_XSS support in CPUID(0xd,i) enumeration Yang Weijiang
2019-11-01  8:52 ` [PATCH v8 2/7] KVM: VMX: Define CET VMCS fields and #CP flag Yang Weijiang
2019-12-10 21:00   ` Sean Christopherson
2019-12-11  1:45     ` Yang Weijiang
2019-11-01  8:52 ` [PATCH v8 3/7] KVM: VMX: Pass through CET related MSRs Yang Weijiang
2019-12-10 21:18   ` Sean Christopherson
2019-12-11  1:32     ` Yang Weijiang
2019-12-11  1:50       ` Sean Christopherson
2019-12-11  2:27         ` Yang Weijiang
2019-12-16  2:18     ` Yang Weijiang
2019-12-18  0:34       ` Sean Christopherson
2019-12-18 13:55         ` Yang Weijiang
2019-12-18 16:02           ` Sean Christopherson
2019-11-01  8:52 ` [PATCH v8 4/7] KVM: VMX: Load CET states on vmentry/vmexit Yang Weijiang
2019-12-10 21:23   ` Sean Christopherson
2019-12-11  1:54     ` Yang Weijiang
2019-12-11 16:35       ` Sean Christopherson [this message]
2019-12-12  1:04         ` Yang Weijiang
2019-12-18  0:30           ` Sean Christopherson
2019-12-18 13:20             ` Yang Weijiang
2019-11-01  8:52 ` [PATCH v8 5/7] KVM: X86: Enable CET bits update in IA32_XSS Yang Weijiang
2019-11-01  8:52 ` [PATCH v8 6/7] KVM: X86: Load guest fpu state when accessing MSRs managed by XSAVES Yang Weijiang
2019-12-10 21:27   ` Sean Christopherson
2019-12-11  2:03     ` Yang Weijiang
2019-11-01  8:52 ` [PATCH v8 7/7] KVM: X86: Add user-space access interface for CET MSRs Yang Weijiang
2019-12-10 21:58   ` Sean Christopherson
2019-12-11  2:19     ` Yang Weijiang
2019-12-11 16:27       ` Sean Christopherson
2019-12-12  0:42         ` Yang Weijiang
2019-12-12 16:03 ` [PATCH v8 0/7] Introduce support for guest CET feature Konrad Rzeszutek Wilk
2019-12-13  0:44   ` Yang Weijiang

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