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 05/10] KVM: x86: Remove defunct setting of XCR0 for guest during vCPU create
Date: Mon, 20 Sep 2021 17:02:58 -0700 [thread overview]
Message-ID: <20210921000303.400537-6-seanjc@google.com> (raw)
In-Reply-To: <20210921000303.400537-1-seanjc@google.com>
Drop code to initialize XCR0 during fx_init(), a.k.a. vCPU creation, as
XCR0 has been initialized during kvm_vcpu_reset() (for RESET) since
commit a554d207dc46 ("KVM: X86: Processor States following Reset or INIT").
Back when XCR0 support was added by commit 2acf923e38fb ("KVM: VMX:
Enable XSAVE/XRSTOR for guest"), KVM didn't differentiate between RESET
and INIT. Ignoring the fact that calling fx_init() for INIT is obviously
wrong, e.g. FPU state after INIT is not the same as after RESET, setting
XCR0 in fx_init() was correct.
Eventually fx_init() got moved to kvm_arch_vcpu_init(), a.k.a. vCPU
creation (ignore the terrible name) by commit 0ee6a5172573 ("x86/fpu,
kvm: Simplify fx_init()"). Finally, commit 95a0d01eef7a ("KVM: x86: Move
all vcpu init code into kvm_arch_vcpu_create()") killed off
kvm_arch_vcpu_init(), leaving behind the oddity of redundant setting of
guest state during vCPU creation.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e0bff5473813..6fd3fe21863e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -993,7 +993,7 @@ static int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
/*
* Do not allow the guest to set bits that we do not support
* saving. However, xcr0 bit 0 is always set, even if the
- * emulated CPU does not support XSAVE (see fx_init).
+ * emulated CPU does not support XSAVE (see kvm_vcpu_reset()).
*/
valid_bits = vcpu->arch.guest_supported_xcr0 | XFEATURE_MASK_FP;
if (xcr0 & ~valid_bits)
@@ -10623,11 +10623,6 @@ static void fx_init(struct kvm_vcpu *vcpu)
if (boot_cpu_has(X86_FEATURE_XSAVES))
vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
host_xcr0 | XSTATE_COMPACTION_ENABLED;
-
- /*
- * Ensure guest xcr0 is valid for loading
- */
- vcpu->arch.xcr0 = XFEATURE_MASK_FP;
}
void kvm_free_guest_fpu(struct kvm_vcpu *vcpu)
--
2.33.0.464.g1972c5931b-goog
next prev parent reply other threads:[~2021-09-21 2:09 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 ` [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 ` Sean Christopherson [this message]
2021-09-21 14:37 ` [PATCH v2 05/10] KVM: x86: Remove defunct setting of XCR0 for guest " 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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