From: Sean Christopherson <seanjc@google.com>
To: Chao Gao <chao.gao@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.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,
Zeng Guang <guang.zeng@intel.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Subject: Re: [PATCH 02/11] KVM: VMX: Handle APIC-write offset wrangling in VMX code
Date: Tue, 15 Feb 2022 16:30:44 +0000 [thread overview]
Message-ID: <YgvVNNvx4NGDSGUA@google.com> (raw)
In-Reply-To: <20220215022221.GA28478@gao-cwp>
On Tue, Feb 15, 2022, Chao Gao wrote:
> >--- a/arch/x86/kvm/vmx/vmx.c
> >+++ b/arch/x86/kvm/vmx/vmx.c
> >@@ -5302,9 +5302,16 @@ static int handle_apic_eoi_induced(struct kvm_vcpu *vcpu)
> > static int handle_apic_write(struct kvm_vcpu *vcpu)
> > {
> > unsigned long exit_qualification = vmx_get_exit_qual(vcpu);
> >- u32 offset = exit_qualification & 0xfff;
> >
> >- /* APIC-write VM exit is trap-like and thus no need to adjust IP */
> >+ /*
> >+ * APIC-write VM-Exit is trap-like, KVM doesn't need to advance RIP and
> >+ * hardware has done any necessary aliasing, offset adjustments, etc...
> >+ * for the access. I.e. the correct value has already been written to
> >+ * the vAPIC page for the correct 16-byte chunk. KVM needs only to
> >+ * retrieve the register value and emulate the access.
> >+ */
> >+ u32 offset = exit_qualification & 0xff0;
>
> Can we take this opportunity to remove offset/exit_qualification?
> They are used just once.
Definitely should have dropped exit_qualification, not sure why I didn't.
I'd prefer to keep offset to document what is held in vmcs.EXIT_QUALIFICATION
without having to add an explicit comment.
next prev parent reply other threads:[~2022-02-15 16:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-04 21:41 [PATCH 00/11] KVM: x86: Prep work for VMX IPI virtualization Sean Christopherson
2022-02-04 21:41 ` [PATCH 01/11] Revert "svm: Add warning message for AVIC IPI invalid target" Sean Christopherson
2022-02-07 16:44 ` Paolo Bonzini
2022-02-04 21:41 ` [PATCH 02/11] KVM: VMX: Handle APIC-write offset wrangling in VMX code Sean Christopherson
2022-02-15 2:22 ` Chao Gao
2022-02-15 16:30 ` Sean Christopherson [this message]
2022-02-04 21:41 ` [PATCH 03/11] KVM: x86: Use "raw" APIC register read for handling APIC-write VM-Exit Sean Christopherson
2022-02-04 21:41 ` [PATCH 04/11] KVM: SVM: Use common kvm_apic_write_nodecode() for AVIC write traps Sean Christopherson
2022-02-04 23:14 ` kernel test robot
2022-02-04 23:14 ` kernel test robot
2022-02-07 16:16 ` Sean Christopherson
2022-02-07 16:16 ` Sean Christopherson
2022-02-04 21:41 ` [PATCH 05/11] KVM: SVM: Don't rewrite guest ICR on AVIC IPI virtualization failure Sean Christopherson
2022-02-04 21:42 ` [PATCH 06/11] KVM: x86: WARN if KVM emulates an IPI without clearing the BUSY flag Sean Christopherson
2022-02-04 21:42 ` [PATCH 07/11] KVM: x86: Make kvm_lapic_reg_{read,write}() static Sean Christopherson
2022-02-04 21:42 ` [PATCH 08/11] KVM: x86: Add helpers to handle 64-bit APIC MSR read/writes Sean Christopherson
2022-02-04 21:42 ` [PATCH 09/11] KVM: x86: Treat x2APIC's ICR as a 64-bit register, not two 32-bit regs Sean Christopherson
2022-02-15 3:27 ` Chao Gao
2022-02-15 16:40 ` Sean Christopherson
2022-02-04 21:42 ` [PATCH 10/11] KVM: x86: Make kvm_lapic_set_reg() a "private" xAPIC helper Sean Christopherson
2022-02-04 21:42 ` [PATCH 11/11] KVM: selftests: Add test to verify KVM handles x2APIC ICR=>ICR2 dance Sean Christopherson
2022-02-24 14:58 ` [PATCH 00/11] KVM: x86: Prep work for VMX IPI virtualization Paolo Bonzini
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