From: Chenyi Qiang <chenyi.qiang@intel.com>
To: Sean Christopherson <sean.j.christopherson@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>,
"Li, Xiaoyao" <xiaoyao.li@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RESEND v4 1/2] KVM: VMX: Convert vcpu_vmx.exit_reason to a union
Date: Mon, 26 Oct 2020 13:31:06 +0800 [thread overview]
Message-ID: <d547ba33-668e-dce5-9c9b-b24c78ebf9e4@intel.com> (raw)
In-Reply-To: <20201020220158.GA9031@linux.intel.com>
On 10/21/2020 6:01 AM, Sean Christopherson wrote:
> On Mon, Oct 12, 2020 at 11:35:41AM +0800, Chenyi Qiang wrote:
>> From: Sean Christopherson <sean.j.christopherson@intel.com>
>>
>> Convert vcpu_vmx.exit_reason from a u32 to a union (of size u32). The
>> full VM_EXIT_REASON field is comprised of a 16-bit basic exit reason in
>> bits 15:0, and single-bit modifiers in bits 31:16.
>>
>> Historically, KVM has only had to worry about handling the "failed
>> VM-Entry" modifier, which could only be set in very specific flows and
>> required dedicated handling. I.e. manually stripping the FAILED_VMENTRY
>> bit was a somewhat viable approach. But even with only a single bit to
>> worry about, KVM has had several bugs related to comparing a basic exit
>> reason against the full exit reason store in vcpu_vmx.
>>
>> Upcoming Intel features, e.g. SGX, will add new modifier bits that can
>> be set on more or less any VM-Exit, as opposed to the significantly more
>> restricted FAILED_VMENTRY, i.e. correctly handling everything in one-off
>> flows isn't scalable. Tracking exit reason in a union forces code to
>> explicitly choose between consuming the full exit reason and the basic
>> exit, and is a convenient way to document and access the modifiers.
>>
>> No functional change intended.
>>
>> Cc: Xiaoyao Li <xiaoyao.li@intel.com>
>> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
>
> This needs your SOB since you are involved in the handling of the patch.
Sorry for the late response, my mailbox encountered some issues...
Will add the SOB here.
>
next prev parent reply other threads:[~2020-10-26 5:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-12 3:35 [RESEND v4 0/2] Add bus lock VM exit support Chenyi Qiang
2020-10-12 3:35 ` [RESEND v4 1/2] KVM: VMX: Convert vcpu_vmx.exit_reason to a union Chenyi Qiang
2020-10-20 22:01 ` Sean Christopherson
2020-10-26 5:31 ` Chenyi Qiang [this message]
2020-10-12 3:35 ` [RESEND v4 2/2] KVM: VMX: Enable bus lock VM exit Chenyi Qiang
2020-10-20 22:19 ` Sean Christopherson
2020-10-26 5:31 ` Chenyi Qiang
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