Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH 2/2] KVM: x86: Fix split-irqchip vs interrupt injection
 window request
To:     Sean Christopherson <seanjc@google.com>,
        Lai Jiangshan <jiangshanlai+lkml@gmail.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, kvm@vger.kernel.org,
        Filippo Sironi <sironi@amazon.de>,
        David Woodhouse <dwmw@amazon.co.uk>,
        "v4.7+" <stable@vger.kernel.org>,
        Wanpeng Li <wanpengli@tencent.com>
References: <20201127112114.3219360-1-pbonzini@redhat.com>
 <20201127112114.3219360-3-pbonzini@redhat.com>
 <CAJhGHyCdqgtvK98_KieG-8MUfg1Jghd+H99q+FkgL0ZuqnvuAw@mail.gmail.com>
 <YHS/BxMiO6I1VOEY@google.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <4a9e11b1-9cd6-b9a4-d9ea-f2f4d0983084@redhat.com>
Date:   Tue, 13 Apr 2021 14:10:02 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.7.0
MIME-Version: 1.0
In-Reply-To: <YHS/BxMiO6I1VOEY@google.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 12/04/21 23:43, Sean Christopherson wrote:
> where kvm_arch_interrupt_allowed() checks EFLAGS.IF (and an edge case related to
> nested virtualization).  KVM also captures EFLAGS.IF in vcpu->run->if_flag.
> For whatever reason, QEMU checks both vcpu->run flags before injecting an IRQ,
> maybe to handle a case where QEMU itself clears EFLAGS.IF?

It's mostly obsolete code (that will be deprecated in the next version 
and removed in about a year) so I wouldn't read much into it.  if_flag 
itself is obsolete; it is not provided by SEV-ES, and a useless subset 
of ready_for_interrupt_injection.

Paolo