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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 02/10] KVM: x86: Clear KVM's cached guest CR3 at RESET/INIT
Date: Mon, 20 Sep 2021 17:02:55 -0700	[thread overview]
Message-ID: <20210921000303.400537-3-seanjc@google.com> (raw)
In-Reply-To: <20210921000303.400537-1-seanjc@google.com>

Explicitly zero the guest's CR3 and mark it available+dirty at RESET/INIT.
Per Intel's SDM and AMD's APM, CR3 is zeroed at both RESET and INIT.  For
RESET, this is a nop as vcpu is zero-allocated.  For INIT, the bug has
likely escaped notice because no firmware/kernel puts its page tables root
at PA=0, let alone relies on INIT to get the desired CR3 for such page
tables.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/x86.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e77a5bf2d940..2cb38c67ed43 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10899,6 +10899,9 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
 	kvm_rip_write(vcpu, 0xfff0);
 
+	vcpu->arch.cr3 = 0;
+	kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3);
+
 	/*
 	 * CR0.CD/NW are set on RESET, preserved on INIT.  Note, some versions
 	 * of Intel's SDM list CD/NW as being set on INIT, but they contradict
-- 
2.33.0.464.g1972c5931b-goog


  parent reply	other threads:[~2021-09-21  2:08 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 ` Sean Christopherson [this message]
2021-09-21 13:52   ` [PATCH v2 02/10] KVM: x86: Clear KVM's cached guest CR3 at RESET/INIT 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 ` [PATCH v2 04/10] KVM: x86: Remove defunct setting of CR0.ET for guests during vCPU create Sean Christopherson
2021-09-21 14:23   ` 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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