From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 DB61C2F5311 for ; Tue, 3 Feb 2026 20:06:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770149193; cv=none; b=uQYwbSkA5IDY8Fvf15zNgGE9f9zQU1smaXEBAOKav0rlNBEgZwMFHnAnbzbVgVoWnrhG4hkY9LpjCa3URxYn7QwGWDgGLZwQ6J82mghf2jeTwT/VybkS8lLfeK/2WcIfCKGrq/awf67K9ygyvJgcEXbJUyYtpCYjwiwdza+EMcU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770149193; c=relaxed/simple; bh=1Ib3pwxKHmKqNzWuh8gauUn0Z+GM1AdBwnBeI2qs2L0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=YGYRhLVS8W+8otIHJDa5hEQXmE+EKsb5EA3jwqy+qp4lP3H1NjMZn/LXemgcWkmE6yt0HiJgXbmy1rTtkBNRgXBG2/ijf+qEzZDmkNPMBuYnIMXADyCKOQIzrMSstxqYtdWWOnpbHLorbqJGMuBWmr3hhqJ3zEwaT7QpygihvJw= 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=3O+5qWUx; arc=none smtp.client-ip=209.85.214.201 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="3O+5qWUx" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2a13cd9a784so52985635ad.2 for ; Tue, 03 Feb 2026 12:06:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1770149191; x=1770753991; 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=RxuGQhnhiUSSgKfkg98kr3VXsZ5hp0LNlVLYQ5k5le4=; b=3O+5qWUxTbXha7H06Qw+p3w3XCo1xA8rcg2eMapbBKt+mR57K+3LsUe2TWd0A7QLjO dm1CZh/ggxh2JZu2RGNB2cfl3+pJVWXAUm+5ekRH2Fl+Kn9AN2EICxY7l5LpPI6ydOz2 w6lcrjkr0gaH7PA8s+oXcgXTPfkxME5ilZafzBmUGE2jMC6FvGna8828s8QCdhm5d74x maC43RaiDYXldAqVdZo6FPryAGralXP7vydD2U1iYhgNYlGI8QCfh335Efphl9n8VAGe fm5zPjKXefxWHDC+cix+WOxq0K1ENyG+2w+4kpVeREIz+Iq8igoFBQyatne55VIN2LjW h8sQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770149191; x=1770753991; 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=RxuGQhnhiUSSgKfkg98kr3VXsZ5hp0LNlVLYQ5k5le4=; b=Yi0JhRQ3DqNhCp+dODVkubvmFoK1gZqMQwneIsVQdMIrSA/B1j3Hs6XlS6YF65SKq2 VMt4nSgq8A2PM9+3v1GxTbQUCzy8n7Ega3cRKY+eZ0JXc/GsTBXpGQT0enzTm2WaQVHO GykWl2PUP54mUTEcgMmRZRAmvADIOBIETgoNDmUdgmMuMJBC4dPnaPcHBOhtbW6KMARQ WRtFAMAuD3s+kz2DvM2LEkqL2nPRSBK/oVADK0D6O7vXLO218ia4QD44n+kL2cMEVEay NWvZ0Gc4PMb4id9/HUGXpTxP2H1no25h7VMpvHL8X+wJ9zepFd8vSVGHoliQo1b1lCdu IzIA== X-Forwarded-Encrypted: i=1; AJvYcCVSUpTRIaFSc0Jw3uMUtEidW9KkEWuT639Gfsmipx5UDsE4daRHXgrYUtPqAVbv9Mxa/bp3CVS6M8rnTjw=@vger.kernel.org X-Gm-Message-State: AOJu0Yz1te725GkNGr6e9SQuqXn/gu2Epr1V8UVgVeXsPOrCFmmAkYk0 JZC+r2qn4mHmw9dtHMip7DRfZ2OGtHdRwKe90MzuSqsobAjwXRjHV6BCRc9FVHsHfaQJr+xsv+0 a+8cuwA== X-Received: from plhn5.prod.google.com ([2002:a17:903:1105:b0:2a7:62c7:4431]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:983:b0:2a7:d7b8:7661 with SMTP id d9443c01a7336-2a933ce935emr4755565ad.4.1770149191214; Tue, 03 Feb 2026 12:06:31 -0800 (PST) Date: Tue, 3 Feb 2026 12:06:29 -0800 In-Reply-To: <1c4bdb3613ebaf65b5dcf9a2268b06fa0c5a6ef3.camel@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260129011517.3545883-1-seanjc@google.com> <20260129011517.3545883-3-seanjc@google.com> <1c4bdb3613ebaf65b5dcf9a2268b06fa0c5a6ef3.camel@intel.com> Message-ID: Subject: Re: [RFC PATCH v5 02/45] KVM: x86/mmu: Update iter->old_spte if cmpxchg64 on mirror SPTE "fails" From: Sean Christopherson To: Kai Huang Cc: "x86@kernel.org" , "dave.hansen@linux.intel.com" , "kas@kernel.org" , "bp@alien8.de" , "mingo@redhat.com" , "pbonzini@redhat.com" , "tglx@kernel.org" , Rick P Edgecombe , "ackerleytng@google.com" , "sagis@google.com" , Vishal Annapurve , "linux-kernel@vger.kernel.org" , Yan Y Zhao , Xiaoyao Li , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , Isaku Yamahata , "binbin.wu@linux.intel.com" Content-Type: text/plain; charset="us-ascii" On Tue, Feb 03, 2026, Kai Huang wrote: > On Wed, 2026-01-28 at 17:14 -0800, Sean Christopherson wrote: > > Pass a pointer to iter->old_spte, not simply its value, when setting an > > external SPTE in __tdp_mmu_set_spte_atomic(), so that the iterator's value > > will be updated if the cmpxchg64 to freeze the mirror SPTE fails. The bug > > is currently benign as TDX is mutualy exclusive with all paths that do > > "local" retry", e.g. clear_dirty_gfn_range() and wrprot_gfn_range(). > > > > Fixes: 77ac7079e66d ("KVM: x86/tdp_mmu: Propagate building mirror page tables") > > Signed-off-by: Sean Christopherson > > Reviewed-by: Kai Huang > > Btw, do we need to cc stable? Probably not? The bug is benign until dirty logging comes along, and if someone backports that support (if it ever manifests) to an older kernel, it's firmly that person's responsibility to pick up dependencies like this.