From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@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: Re: [PATCH v2 06/10] KVM: x86: Fold fx_init() into kvm_arch_vcpu_create()
Date: Tue, 21 Sep 2021 16:52:16 +0200 [thread overview]
Message-ID: <87tuie7zhb.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20210921000303.400537-7-seanjc@google.com>
Sean Christopherson <seanjc@google.com> writes:
> Move the few bits of relevant fx_init() code into kvm_arch_vcpu_create(),
> dropping the superfluous check on vcpu->arch.guest_fpu that was blindly
> and wrongly added by commit ed02b213098a ("KVM: SVM: Guest FPU state
> save/restore not needed for SEV-ES guest").
I have more questions to the above mentioned commit: why is it OK to
'return 0' from kvm_vcpu_ioctl_x86_set_xsave() without writing anything
to 'guest_xsave'? Same goes to kvm_arch_vcpu_ioctl_get_fpu(). Whould't
it be better to throw an error as we can't actually get this information
for encrypted guests? It's probably too late to change this now I
suppose ...
>
> Note, KVM currently allocates and then frees FPU state for SEV-ES guests,
> rather than avoid the allocation in the first place. While that approach
> is inarguably inefficient and unnecessary, it's a cleanup for the future.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/x86.c | 16 ++++------------
> 1 file changed, 4 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6fd3fe21863e..ec61b90d9b73 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10614,17 +10614,6 @@ static int sync_regs(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> -static void fx_init(struct kvm_vcpu *vcpu)
> -{
> - if (!vcpu->arch.guest_fpu)
> - return;
> -
> - fpstate_init(&vcpu->arch.guest_fpu->state);
> - if (boot_cpu_has(X86_FEATURE_XSAVES))
> - vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
> - host_xcr0 | XSTATE_COMPACTION_ENABLED;
> -}
> -
> void kvm_free_guest_fpu(struct kvm_vcpu *vcpu)
> {
> if (vcpu->arch.guest_fpu) {
> @@ -10703,7 +10692,10 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> pr_err("kvm: failed to allocate vcpu's fpu\n");
> goto free_user_fpu;
> }
> - fx_init(vcpu);
> + fpstate_init(&vcpu->arch.guest_fpu->state);
> + if (boot_cpu_has(X86_FEATURE_XSAVES))
> + vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
> + host_xcr0 | XSTATE_COMPACTION_ENABLED;
>
> vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
> vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
next prev parent reply other threads:[~2021-09-21 14:52 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 ` [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 [this message]
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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