From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 9CBDA2652B7 for ; Wed, 25 Feb 2026 01:21:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771982478; cv=none; b=d50Nfve4MNKmvE+GpBLOHeHidzCtHLwogQtSyY19SuX77Jz5uMmO31r6FbEdduwvXcCpopJCA6ztF5pmIsy1TWic3lfGLN+a607R58l/ohmv4cwtGnVoWGBhQnaBGSR8gqhxqoWPDZo0+k5zHGVxsX2ZOfca44k9VFRtWo+NG8s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771982478; c=relaxed/simple; bh=Qy31+uRAyXc552YjYjFbiMoMOXbW3e9UP2BZgteKHMs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=QSxjpmL9A+jWNrmy0LiesOTaXrIYEVFIZoIOCiEQj5FrbwQUMaMCyiXsnhR5hMoDnCauOMIYLhRAPE9o1aK1MchTf5V46JJdYpCc//ebw3PV8pGC/uvE4cH4gDUMrO5KJinTjSqJ4EMGI8q36hM+AvfhvtJ7huXA6Ls048zBsQM= 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=zH1okmbq; arc=none smtp.client-ip=209.85.216.74 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="zH1okmbq" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-358f058973fso906327a91.1 for ; Tue, 24 Feb 2026 17:21:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1771982477; x=1772587277; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=LC9/uqgNjMKR3Pk2VQH/jaz/lG7goMkRYlbLKdqdUyY=; b=zH1okmbqk7N039NOHaa7iZu7VCsU59eWPClkOHV62+tC+WvWTXksNXYyxMfvikYiVK N0UnKPFYdwmB4C+G408v4rAQJj/xXpC9XBFDs1CCbNcC4m/WFfWCpWpYlC6DrDANKXF+ UE1FqGWpX3Sel3Ta8mk7Y3LqtndiPn/fM1NOPqW54l9woHTnu9ZS7q9/hHykGeyWXbwc AutQdKJRNvw4h4/bQ5YaX2vQQgOlRUlMnc7YMzVvL3jWSs5NqjIxAivCDKoytSWb+6EW LUah5xsfGVcTR+jEQ6F3wB1jQBNFzRY/bDC1mW3yCHOpdAew93EKY+XL4PJ9waPCiVo9 NUOw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771982477; x=1772587277; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=LC9/uqgNjMKR3Pk2VQH/jaz/lG7goMkRYlbLKdqdUyY=; b=lQnWPvF+hR9Xmg6PWEp5yeVSes9SkNmW64Kw5J1NB2p6a5K2Ul4pqF3pVFF/OC8xAl 0d5fus3a7baEjAlzZ0dtEHr2tzO8T4kbDY7mg8XNo2dkVgcB8YUdjzNsstwXcQuDEjI3 jIogRuHkZptk2TUAyp3rzfgs4nWSMXaa7nOvJGbKJHq+Zo2bp+mVlIPyksOUH+zvLUSp r383ArqLm5+x3XHpiStD/GHTNZprgT8Ye6ow5EEfFjJjKMYBrShzyXFBiRBACDqrQ45p JIpk1Xyq+qiU4o4KTdbjsCoTzfB7OS101zp1RL8b7QK+vkitm7WM+l4DR0LIaj/nxPXi MZIg== X-Forwarded-Encrypted: i=1; AJvYcCXPtamxe+ZX0sf3IP0vN+xMLyHaxO6Faz13AOALPYC2Cnk2IXMwj4Z3mmArtBhptS75hrt5RBk8FF8Lw3I=@vger.kernel.org X-Gm-Message-State: AOJu0YyrPqdAHK1de+sNj39fFbzwv6h5a/A8baw1AFmrjoSN7wRodIe+ EkxtHI258px09KN8V/9goAZm2W/PV/LNLViZqxoZkd2sNELZxrK8vsVwOqTGxiVBcdZ58dfAg1g hpxwQ7Q== X-Received: from pgbcz10.prod.google.com ([2002:a05:6a02:230a:b0:c6d:cb1b:286e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:6a04:b0:394:8455:d1a9 with SMTP id adf61e73a8af0-39545e5081dmr10146147637.2.1771982476785; Tue, 24 Feb 2026 17:21:16 -0800 (PST) Reply-To: Sean Christopherson Date: Tue, 24 Feb 2026 17:20:48 -0800 In-Reply-To: <20260225012049.920665-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260225012049.920665-1-seanjc@google.com> X-Mailer: git-send-email 2.53.0.414.gf7e9f6c205-goog Message-ID: <20260225012049.920665-14-seanjc@google.com> Subject: [PATCH 13/14] KVM: x86: Don't panic the kernel if completing userspace I/O / MMIO goes sideways From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini , Kiryl Shutsemau Cc: kvm@vger.kernel.org, x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, Yashu Zhang , Rick Edgecombe , Binbin Wu , Xiaoyao Li , Tom Lendacky , Michael Roth Content-Type: text/plain; charset="UTF-8" Kill the VM instead of the host kernel if KVM botches I/O and/or MMIO handling. There is zero danger to the host or guest, i.e. panicking the host isn't remotely justified. Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f3e2ec7e1828..5376b370b4db 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9710,7 +9710,8 @@ static int complete_fast_pio_in(struct kvm_vcpu *vcpu) unsigned long val; /* We should only ever be called with arch.pio.count equal to 1 */ - BUG_ON(vcpu->arch.pio.count != 1); + if (KVM_BUG_ON(vcpu->arch.pio.count != 1, vcpu->kvm)) + return -EIO; if (unlikely(!kvm_is_linear_rip(vcpu, vcpu->arch.cui_linear_rip))) { vcpu->arch.pio.count = 0; @@ -11820,7 +11821,8 @@ static inline int complete_emulated_io(struct kvm_vcpu *vcpu) static int complete_emulated_pio(struct kvm_vcpu *vcpu) { - BUG_ON(!vcpu->arch.pio.count); + if (KVM_BUG_ON(!vcpu->arch.pio.count, vcpu->kvm)) + return -EIO; return complete_emulated_io(vcpu); } @@ -11849,7 +11851,8 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu) struct kvm_mmio_fragment *frag; unsigned len; - BUG_ON(!vcpu->mmio_needed); + if (KVM_BUG_ON(!vcpu->mmio_needed, vcpu->kvm)) + return -EIO; /* Complete previous fragment */ frag = &vcpu->mmio_fragments[vcpu->mmio_cur_fragment]; @@ -14262,7 +14265,8 @@ static int complete_sev_es_emulated_mmio(struct kvm_vcpu *vcpu) struct kvm_mmio_fragment *frag; unsigned int len; - BUG_ON(!vcpu->mmio_needed); + if (KVM_BUG_ON(!vcpu->mmio_needed, vcpu->kvm)) + return -EIO; /* Complete previous fragment */ frag = &vcpu->mmio_fragments[vcpu->mmio_cur_fragment]; -- 2.53.0.414.gf7e9f6c205-goog