linux-kernel - Re: [PATCH v4 00/11] KVM: VMX: Clean up Hyper-V PV TLB flush

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Date:   Tue, 9 Mar 2021 09:35:05 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v4 00/11] KVM: VMX: Clean up Hyper-V PV TLB flush

On 09/03/21 02:18, Sean Christopherson wrote:
> Maybe this series is cursed.  The first patch got mangled and broke SME.
> It shows up as two commits with the same changelog, so maybe you intended to
> split the patch and things went sideways?

There was a conflict.  I admit kvm/queue is not always that good, 
usually I try to test it but yesterday I just didn't have time.

I'll fix up everything (also 20/24 in the other series).

Oh well, you have to break eggs to make an omelette. :)

Paolo

> Anyways, commit a16241ae56fa ("KVM: x86: Get active PCID only when writing a
> CR3 value") breaks SME and PCID.  The kvm/queue code looks like this:
> 
> 
> 	cr3 = __sme_set(root_hpa);
> 	if (npt_enabled) {
> 		svm->vmcb->control.nested_cr3 = root_hpa;
> 		vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
> 
> 		/* Loading L2's CR3 is handled by enter_svm_guest_mode.  */
> 		if (!test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
> 			return;
> 		cr3 = vcpu->arch.cr3;
> 	}
> 
> 	svm->vmcb->save.cr3 = cr3;
> 	vmcb_mark_dirty(svm->vmcb, VMCB_CR);
> 
> but it should look like this:
> 
> 	if (npt_enabled) {
> 		svm->vmcb->control.nested_cr3 = __sme_set(root);
> 		vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
> 
> 		/* Loading L2's CR3 is handled by enter_svm_guest_mode.  */
> 		if (!test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
> 			return;
> 		cr3 = vcpu->arch.cr3;
> 	} else if (vcpu->arch.mmu->shadow_root_level >= PT64_ROOT_4LEVEL) {
> 		cr3 = __sme_set(root);
> 	} else {
> 		cr3 = root;
> 	}
> 
> 	svm->vmcb->save.cr3 = cr3;
> 	vmcb_mark_dirty(svm->vmcb, VMCB_CR);
> 
> I'll generate a delta patch, and test and post, just in case there is other
> stuff that got lost.
>