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([2001:b07:6468:f312:1c09:f536:3de6:228c]) by smtp.googlemail.com with ESMTPSA id cr10-20020a056402222a00b0041d918fdf99sm8817933edb.85.2022.04.27.09.19.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Apr 2022 09:19:37 -0700 (PDT) Message-ID: Date: Wed, 27 Apr 2022 18:19:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH MANUALSEL 5.15 5/7] KVM: x86: Do not change ICR on write to APIC_SELF_IPI Content-Language: en-US To: Sasha Levin , linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Chao Gao , Sean Christopherson , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org References: <20220427155431.19458-1-sashal@kernel.org> <20220427155431.19458-5-sashal@kernel.org> From: Paolo Bonzini In-Reply-To: <20220427155431.19458-5-sashal@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/27/22 17:54, Sasha Levin wrote: > From: Paolo Bonzini > > [ Upstream commit d22a81b304a27fca6124174a8e842e826c193466 ] > > Emulating writes to SELF_IPI with a write to ICR has an unwanted side effect: > the value of ICR in vAPIC page gets changed. The lists SELF_IPI as write-only, > with no associated MMIO offset, so any write should have no visible side > effect in the vAPIC page. > > Reported-by: Chao Gao > Reviewed-by: Sean Christopherson > Signed-off-by: Paolo Bonzini > Signed-off-by: Sasha Levin > --- > arch/x86/kvm/lapic.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 4d92fb4fdf69..83d1743a1dd0 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -2125,10 +2125,9 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val) > break; > > case APIC_SELF_IPI: > - if (apic_x2apic_mode(apic)) { > - kvm_lapic_reg_write(apic, APIC_ICR, > - APIC_DEST_SELF | (val & APIC_VECTOR_MASK)); > - } else > + if (apic_x2apic_mode(apic)) > + kvm_apic_send_ipi(apic, APIC_DEST_SELF | (val & APIC_VECTOR_MASK), 0); > + else > ret = 1; > break; > default: Acked-by: Paolo Bonzini