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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Reiji Watanabe <reijiw@google.com>
Subject: [PATCH v2 04/10] KVM: x86: Remove defunct setting of CR0.ET for guests during vCPU create
Date: Mon, 20 Sep 2021 17:02:57 -0700	[thread overview]
Message-ID: <20210921000303.400537-5-seanjc@google.com> (raw)
In-Reply-To: <20210921000303.400537-1-seanjc@google.com>

Drop code to set CR0.ET for the guest during initialization of the guest
FPU.  The code was added as a misguided bug fix by commit 380102c8e431
("KVM Set the ET flag in CR0 after initializing FX") to resolve an issue
where vcpu->cr0 (now vcpu->arch.cr0) was not correctly initialized on SVM
systems.  While init_vmcb() did set CR0.ET, it only did so in the VMCB,
and subtly did not update vcpu->cr0.  Stuffing CR0.ET worked around the
immediate problem, but did not fix the real bug of vcpu->cr0 and the VMCB
being out of sync.  That underlying bug was eventually remedied by commit
18fa000ae453 ("KVM: SVM: Reset cr0 properly on vcpu reset").

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/x86.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ab907a0b9eeb..e0bff5473813 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10628,8 +10628,6 @@ static void fx_init(struct kvm_vcpu *vcpu)
 	 * Ensure guest xcr0 is valid for loading
 	 */
 	vcpu->arch.xcr0 = XFEATURE_MASK_FP;
-
-	vcpu->arch.cr0 |= X86_CR0_ET;
 }
 
 void kvm_free_guest_fpu(struct kvm_vcpu *vcpu)
-- 
2.33.0.464.g1972c5931b-goog


  parent reply	other threads:[~2021-09-21  2:10 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-21  0:02 [PATCH v2 00/10] KVM: x86: Clean up RESET "emulation" Sean Christopherson
2021-09-21  0:02 ` [PATCH v2 01/10] KVM: x86: Mark all registers as avail/dirty at vCPU creation Sean Christopherson
2021-09-21 13:40   ` Vitaly Kuznetsov
2021-09-21  0:02 ` [PATCH v2 02/10] KVM: x86: Clear KVM's cached guest CR3 at RESET/INIT Sean Christopherson
2021-09-21 13:52   ` Vitaly Kuznetsov
2021-09-21 13:55     ` Vitaly Kuznetsov
2021-09-21 17:35   ` Paolo Bonzini
2021-09-21  0:02 ` [PATCH v2 03/10] KVM: x86: Do not mark all registers as avail/dirty during RESET/INIT Sean Christopherson
2021-09-21  0:02 ` Sean Christopherson [this message]
2021-09-21 14:23   ` [PATCH v2 04/10] KVM: x86: Remove defunct setting of CR0.ET for guests during vCPU create Vitaly Kuznetsov
2021-09-21  0:02 ` [PATCH v2 05/10] KVM: x86: Remove defunct setting of XCR0 for guest " Sean Christopherson
2021-09-21 14:37   ` Vitaly Kuznetsov
2021-09-21  0:02 ` [PATCH v2 06/10] KVM: x86: Fold fx_init() into kvm_arch_vcpu_create() Sean Christopherson
2021-09-21 14:52   ` Vitaly Kuznetsov
2021-10-06 23:04     ` Sean Christopherson
2021-09-21  0:03 ` [PATCH v2 07/10] KVM: VMX: Drop explicit zeroing of MSR guest values at vCPU creation Sean Christopherson
2021-09-21 15:02   ` Vitaly Kuznetsov
2021-09-21  0:03 ` [PATCH v2 08/10] KVM: VMX: Move RESET emulation to vmx_vcpu_reset() Sean Christopherson
2021-09-21  0:03 ` [PATCH v2 09/10] KVM: SVM: Move RESET emulation to svm_vcpu_reset() Sean Christopherson
2021-09-21  0:03 ` [PATCH v2 10/10] KVM: x86: WARN on non-zero CRs at RESET to detect improper initalization Sean Christopherson
2021-09-21 13:59   ` Vitaly Kuznetsov
2021-09-23 16:23 ` [PATCH v2 00/10] KVM: x86: Clean up RESET "emulation" Paolo Bonzini

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