From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 579EE403AF7 for ; Wed, 10 Jun 2026 12:45:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781095550; cv=none; b=Q4M52pOQV01lt2JkwMKa0Qi0h/P50yghDw+YOUWX4h8t+gfTJKVMiYqlvPKaNCRAYrOGw/cT8P5JCEjowiVc0rsQVLvwGAlLPR9NUkPkt+pGj9V9NhPbz1QsLijfnpTfBtkxUbh9wttCXX4AGUlvgbYAweGDdurMzE8JoGVp1AY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781095550; c=relaxed/simple; bh=ZDtoHAg0RVYLJFl411rVT6pojkbYcRqIGwO9uqRapX0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=k5E9SFx/d1zAcbY4skZrgIgHOD7zn05L/tmnXLP57CoTrUYEQYFCrmMOSX3X+7t8saQD90m6L/ZzyzpIXvy0jaeapA6FVWtbul+rZOwup0AsZhsJkm03wQGp9aHZoXJ5FPRwr/HB7w08WOHgLVb2YfAzX9fJyhMEIN5SX3yYMnU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=mkl1Ngmk; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="mkl1Ngmk" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-c85a2c305d0so3867716a12.1 for ; Wed, 10 Jun 2026 05:45:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1781095549; x=1781700349; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=BekvPjo4s9TiFe+KHAujjPKkPO/Dd5UZ6PvZoUWkBvE=; b=mkl1NgmkhNuqgwdWZVc3nq3ZBi1ysas/5Wqg6bWTJwegC6db/dJo6dfeBre5XZmopu 6DHkfmNcgXqZXLWla0yoBOzhMe6YjNWNLJOJgcZ1p2ttrfZm7aXPrllj73ZHlcgA7/Bk UO/FIkP6nWJ0RSNr9Wc1zKozWa6kRcgNW9457++Ab1a3EoFh8LAoaVCWhUEojFMBmKBt L4g8QkCMtpjwGNzUxd7K9RNHdjIjoG1i7pf+xwI+Ddvki85tk7FRLJKJKH5YKNbvaOjb u8DCEDAgcAsjH3mbNihey9oWl+LyOXi+HdoRMBBvREg3qi4zoOI0xy5IhVyKDkr3d5Ob vR3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781095549; x=1781700349; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=BekvPjo4s9TiFe+KHAujjPKkPO/Dd5UZ6PvZoUWkBvE=; b=ifEStNkOmV9e4cdSPg+hVY3mXz8utEiZUxiLU7TIRNXPtCOMfqO6UY6LniEBqPTSpo Fzl4Vz6OCMhWge0ijaiRKqnkRMVqXnUwuyLQJzKletv1kmW/pzgMtRlz9yzpSawGWu1P OVzyBI74G5WMVitaJSToSSbAT6KuokVv87eh0Jw1IwbZyXHjpeKWORUc5SIsn5cKkTF4 i3y/dwXHI/qMRzmr7JvxBZKC0TNKBoa2vhj2eupx3Wqn3qg3+UUQnekVnF/VyicGuZX7 l6h18x40uZR3DDnY5X2FPJa/yWLuGYmli/f8BnbbQe4LkeT+UpWXbCXDfGQnbxKrSZ/x yRzA== X-Forwarded-Encrypted: i=1; AFNElJ9TeFVX16TDPmNLTq9RZspBrQvzGgY63MxEn78as24hL3SsrlU3FplNb8vRRiu56hdjlJR2LHki6XVT+Ss=@vger.kernel.org X-Gm-Message-State: AOJu0YxRhhzgb1SSawMN5DQHb/8RVnIaPxttWPUM+qIHD6fDF75TqKbJ b8y4h/yecbAvYnKB/JuVtVOnqmgElqj2clIp29/emtaIV8IpiPR20dP/S4Q0wqpu4++IQ3gvbil BzplhTQ== X-Received: from pfms4.prod.google.com ([2002:aa7:8284:0:b0:842:6fe1:8620]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:84b:b0:842:6004:3fd5 with SMTP id d2e1a72fcca58-842b0f4ed9dmr26896280b3a.25.1781095548452; Wed, 10 Jun 2026 05:45:48 -0700 (PDT) Date: Wed, 10 Jun 2026 05:45:47 -0700 In-Reply-To: <20260610070512.85463-1-m18700951735@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260610070512.85463-1-m18700951735@163.com> Message-ID: Subject: Re: [PATCH] KVM: SVM: Clear dummy V_IRQ in vmcb01 when deactivating AVIC From: Sean Christopherson To: xin guo Cc: pbonzini@redhat.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Wed, Jun 10, 2026, xin guo wrote: > When KVM requests an IRQ window via svm_set_vintr(), it programs a > dummy VINTR with int_vector=0 and V_IRQ=1 into the current VMCB. > These int_ctl fields are documented to be ignored while AVIC is > enabled, so the dummy VINTR is harmless during AVIC operation. > > However, avic_deactivate_vmcb() only clears AVIC_ENABLE_MASK and > X2APIC_MODE_MASK, and does not clear the VINTR injection state. Once > AVIC is disabled, hardware honors V_IRQ again and injects vector 0 > into the guest on the next VMRUN. Windows guests observe this as a > spurious interrupt and crash, e.g. with STATUS_INTEGER_DIVIDE_BY_ZERO. Can you provide a reproducer, or at least instructions to reproduce? This feels like we're treating a symptom, not the underlying bug. And while I can definitely see KVM leaving a stale V_IRQ_MASK in vmcb01, I don't see how that can happen while also clearing INTERCEPT_VINTR, as the only place INTERCEPT_VINTR is cleared in vmcb01 is svm_clear_vintr(), which also purges V_IRQ_MASK. svm_clr_intercept(svm, INTERCEPT_VINTR); /* Drop int_ctl fields related to VINTR injection. */ svm->vmcb->control.int_ctl &= ~V_IRQ_INJECTION_BITS_MASK; > Fix this by also clearing V_IRQ_INJECTION_BITS_MASK from vmcb01's > int_ctl in avic_deactivate_vmcb(), so that no stale dummy VINTR is > left behind when AVIC transitions from enabled to disabled. > > Signed-off-by: xin guo > --- > arch/x86/kvm/svm/avic.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c > index cdd5a6dc646f..b042c3f5f90e 100644 > --- a/arch/x86/kvm/svm/avic.c > +++ b/arch/x86/kvm/svm/avic.c > @@ -257,7 +257,9 @@ static void avic_deactivate_vmcb(struct vcpu_svm *svm) > { > struct vmcb *vmcb = svm->vmcb01.ptr; > > - vmcb->control.int_ctl &= ~(AVIC_ENABLE_MASK | X2APIC_MODE_MASK); > + vmcb->control.int_ctl &= ~(AVIC_ENABLE_MASK | X2APIC_MODE_MASK | > + V_IRQ_INJECTION_BITS_MASK); > + > vmcb->control.avic_physical_id &= ~AVIC_PHYSICAL_MAX_INDEX_MASK; > > if (!is_sev_es_guest(&svm->vcpu)) > -- > 2.27.0 >