From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Chenyi Qiang <chenyi.qiang@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>,
Xiaoyao Li <xiaoyao.li@intel.com>,
kvm@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: Tue, 20 Oct 2020 15:01:58 -0700 [thread overview]
Message-ID: <20201020220158.GA9031@linux.intel.com> (raw)
In-Reply-To: <20201012033542.4696-2-chenyi.qiang@intel.com>
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.
next prev parent reply other threads:[~2020-10-20 22:02 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 [this message]
2020-10-26 5:31 ` Chenyi Qiang
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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