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KVM: x86: Remove defunct setting of XCR0 for guest during vCPU create 

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 a554d207dc ("KVM: X86: Processor States following Reset or INIT").

Back when XCR0 support was added by commit 2acf923e38 ("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 0ee6a51725 ("x86/fpu,
kvm: Simplify fx_init()").  Finally, commit 95a0d01eef ("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>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210921000303.400537-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-09-20 17:02:58 -07:00 committed by Paolo Bonzini
parent 5ebbc470d7
commit e8f65b9bb4
1 changed files with 1 additions and 6 deletions
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7
arch/x86/kvm/x86.c
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@ -973,7 +973,7 @@ 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)
@ -10606,11 +10606,6 @@ 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)