From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (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 1CF7D2FC00C for ; Mon, 5 Jan 2026 17:42:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767634941; cv=none; b=rtXg3qXgNomIDd+wsHWkLH0sX9vKGzrUUH0qg+j4411g+r58f7iYLrVM1ouo6ks2Yksm/wY2vEOCEImL7nTR1XoYeUaSTVqVOfU5fpca5isYsqxNF3e+mhI8GND2oCxZR4CPPfv4xvWYS4I1DfUw4XC68ZxXG10DJuNqW5sc8qk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767634941; c=relaxed/simple; bh=4b6ti+RmgfZJNtUxvbEGFQg50xjmQpryddCzAS0dEKg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=oAtdlq1kkTNbsVnmsStrr48TWgnBGpNHZV+spgjTb16zJRtZDz/TdDImi/RXuVgSAXlUAIOA2P/xq5Jv+xe31fZFKkCIuKmo/Zt8uGbcZIwWmvrXRRG7C06Hf9aTVdzFA/uZj2ndBB4KMpC96LpXaDvRsi1MTxjj5DXbo4cSHjo= 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=FkZ2XIFL; arc=none smtp.client-ip=209.85.210.201 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="FkZ2XIFL" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-7f66686710fso430095b3a.3 for ; Mon, 05 Jan 2026 09:42:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1767634939; x=1768239739; 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=rhaaoIrpwKmi1popYwImOlBJQVWglr2lIzlwBR1M0gE=; b=FkZ2XIFLuD8R5qsX3JCJ3TkHBSO/HYVktpzLkIiNK5smNzfrSgMXrQsq1kqCJWktf4 EldMlUksSGJRqkTMpxGehoghkukF5BePehnNoJN2jdyc9TnVsUMt9momIPQ2ukGCUBKk 8QJBwo+cnr4JIZwlEeQlWOJAlIj3vW0vjNf0LWP4xvqGzDjhhfBN/XJ/kNSsZKu9Oo0T 19Bi3H+w7JBVh8MUWJRZlg83SGWeSh3UOlABZC+wjh3H0h7CNa8uV9AvB4EEdvPlv+zC 6coj5cfyl2Dp0f353AMzQS3AzVGM3CEPN+3ttGHFoSVsQUpApq1LdItIv1oVy8GJurFv IBcg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767634939; x=1768239739; 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=rhaaoIrpwKmi1popYwImOlBJQVWglr2lIzlwBR1M0gE=; b=VR2YJ3ovGj/sU3OGNx94IEdJ7q4Rj+AwLANERQi1pq0cVwzI9w0Nm/uUB9WO/Wuagj g7R/h6bA7XTo9PJP7Lb7IW0DgwsvdLO36B9JgckVHf8wS181hXVhbKCrNXMV0CDP3LgK K55jCuE8VuFPMCkJ378x404HbGANNNx+dNCCrjaPQgE8OYS4ZWg7ThewxCoKhGxEKIPb 1l+Gmk+Po8BLbkDTuNJ9dtJT6ALkRHSwccmMQVGamoElIaYgB3ZpGT4hlynAMyrZrhGq jgk/pMIkWXEaNtmo1yv2K+4iYVNkcFiJMbk/+EwaoWjEh7V98404ROV6YyWQLEBEYax/ wL3g== X-Forwarded-Encrypted: i=1; AJvYcCW/LKa4R7a6NIETgZ1e36Zur2g5kYCmkvCMbB2fiB0o3sr6iNjSMBeg5P1jxTPiRWaP5CQ=@vger.kernel.org X-Gm-Message-State: AOJu0Yy8epEJLh/IWhMThpbGxRP1B1C4s3Rj/y9iAuTOlqZyxES3hQs1 WrWQp3qNKCZUXWVZM6kpNd0ozxveyTxPfmNHBHDI1G7ICTg1szFzyNifPl5ZZH3ox4GMXWLjdPZ VSfbw5w== X-Google-Smtp-Source: AGHT+IHVQhNdzqxSBDWtZhkY1cbUxdZB6/e/xfSz8pxhB4np55/4r3z1TMMdoc4zF4qbMHXb5rrPeUwWoP0= X-Received: from pffn21.prod.google.com ([2002:a62:e515:0:b0:7ee:f5f6:a02f]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:3387:b0:35d:53dc:cb56 with SMTP id adf61e73a8af0-389822d69d9mr122558637.36.1767634939225; Mon, 05 Jan 2026 09:42:19 -0800 (PST) Date: Mon, 5 Jan 2026 09:42:17 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251230220220.4122282-1-seanjc@google.com> <20251230220220.4122282-3-seanjc@google.com> Message-ID: Subject: Re: [PATCH v2 2/2] KVM: nVMX: Remove explicit filtering of GUEST_INTR_STATUS from shadow VMCS fields From: Sean Christopherson To: Chao Gao Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Xin Li , Yosry Ahmed Content-Type: text/plain; charset="us-ascii" On Wed, Dec 31, 2025, Chao Gao wrote: > On Tue, Dec 30, 2025 at 02:02:20PM -0800, Sean Christopherson wrote: > >Drop KVM's filtering of GUEST_INTR_STATUS when generating the shadow VMCS > >bitmap now that KVM drops GUEST_INTR_STATUS from the set of supported > >vmcs12 fields if the field isn't supported by hardware. > > IIUC, the construction of the shadow VMCS bitmap and fields doesn't reference > "the set of supported vmcs12 fields". Argh, right you are. I assumed init_vmcs_shadow_fields() would already verify the field is a valid vmcs12 field, at least as a sanity check, but it doesn't. > So, with the filtering dropped, copy_shadow_to_vmcs12() and > copy_vmcs12_to_shadow() may access GUEST_INTR_STATUS on unsupported hardware. > > Do we need something like this (i.e., don't shadow unsupported vmcs12 fields) > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index f50d21a6a2d7..08433b3713d2 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -127,6 +127,8 @@ static void init_vmcs_shadow_fields(void) > continue; > break; > default: > + if (!cpu_has_vmcs12_field(field)) This can be if (get_vmcs12_field_offset(field) < 0) And I think I'll put it outside the switch statement, because the requirement applies to all fields, even those that have additional restrictions. I also think it makes sense to have patch 1 call nested_vmx_setup_vmcs12_fields() from nested_vmx_hardware_setup(), so that the ordering and dependency between configuring vmcs12 fields and shadow VMCS fields can be explicitly documented.