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 C2657192D6A for ; Fri, 30 Aug 2024 13:52:49 +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=1725025971; cv=none; b=V+1UPHhUkZKJEPiUzqGOQ4Tx0LGCXw0RePT46Fn3U+YB0fsmzoh2zGt3/FfnP8fSn8ftcN7J7xbfdyZ8JfRvdW3dbPp0H/Z4LjlxYWPpsXs6yQAOomf5fHXzsVbNxUfEOm4UrhiRnIiY7QPfC3H7YPoA6FWcMhOmw8w8l0+hN3A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725025971; c=relaxed/simple; bh=7VO2YEoc2qaBwPc/ZWWxQx/gNcW0P3fJFQwweSWfe3I=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=PsIJyLeMJeWFiKTWIl/vdE2iDXjKnViYNJPIOYZbONauLwauxWLmBfrU9u6UNVs489x5hRpnVPSTqOr9xzH6H7DjZPCzbM5MK0dOsnoDTS1Hn7w/koMCrG27HMyRN9/61CnBXK1lOSSSm73DSPAzVlmR0OlYDMnzhGBiCSHUZw0= 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=fXWT7AS+; 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="fXWT7AS+" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-201e24bd4d9so17553055ad.0 for ; Fri, 30 Aug 2024 06:52:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1725025969; x=1725630769; 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=VGytXQEPwtv9Mq3qz2G1a6/C8wxSI6csvHwukiIv4rk=; b=fXWT7AS+8dBFndBbDHUOhIUkKLkMrS0ygtvNyCtbN/6zOuFHDyiTxq7jNFKbpKWWF8 T85HDP2P3KA4hA9PS+ySgKvGbKWNaJwhJQcyyDKe3nwOJpDhgsUeVP94UbTGe1NceY7C 1hd1lYOKv9m8kYz0K1OJWyKyHLWpPw9hBj+4hIf+DwVagl0uAq7I3OexOeXVpDJssAnr T08DMMjFcTCry2i6aAj/DHhxnGHeE0cYxQrpP3STNwbkAgQv0tIkJQQAjKVoXMiEgOGO +l5wHbmVhTEW4qj5v2WkqSQenK1sa8/0mia1wFCaImguMOGmK3PUbV/sBSNOVadNF4bf dGjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1725025969; x=1725630769; 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=VGytXQEPwtv9Mq3qz2G1a6/C8wxSI6csvHwukiIv4rk=; b=eL1iPTYenTXpA8Ib0lBLPFbfgFKK89IddYfpO3XkxQeXbDfPDj+jQCIjweRN0JusaD Gyxl+MfbS0POqqnnP67m4csjt6dQqgYt88YLMphRpquba9qEthtvmW5i/U8tMl2c6b0H 7whITdV0sp+h+Cj3Z5tF3djA1E4sVtOQpx8a3/ju7cCXdQmtb5arlVDg5AANxP0g+TgZ tcX30gLbOrH5VN9lWKMe60cAPz65hjnIHRaCEIUanUE9oJZddGQdg9ZnIuSbpIcep1Lb AbSdc2D1ya+llGZ+dJRJizn+IjtTKgLbYmv3g85uOvkpliQC7MLSX1u7XjjwDTFiVKae Au2A== X-Forwarded-Encrypted: i=1; AJvYcCXn8hXeli7vhvfn6PSbRcXGEt76aka90EpfsXvjrAjRKCy7qX/Ga5cg4L1L+YRaLUGTykgUx5oC2jkgPLs=@vger.kernel.org X-Gm-Message-State: AOJu0YwjxDoCEGa7lvhr0IRoFlUWP3w/Y2mDHPSpwJc7dE2GCuRwNc+q Sn9P9cFpqkBZXzZ66iSKZifCw/ZOwRU5Dll22ogBCYPzkyJMEReR8luV6E3DoR6Nd+aZ9wrO6rM FoQ== X-Google-Smtp-Source: AGHT+IGO22ARAD+XDst+l4CutMgZbM838KqS/tPsC9q5mz4asSk4MODrN2e+vIDiQs1MFNh7WOArc932vYQ= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:c412:b0:202:101a:b78e with SMTP id d9443c01a7336-20527a58c87mr431875ad.6.1725025968924; Fri, 30 Aug 2024 06:52:48 -0700 (PDT) Date: Fri, 30 Aug 2024 06:52:47 -0700 In-Reply-To: <871q26unq8.fsf@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240309010929.1403984-1-seanjc@google.com> <20240309010929.1403984-6-seanjc@google.com> <877cbyuzdn.fsf@redhat.com> <871q26unq8.fsf@redhat.com> Message-ID: Subject: Re: [PATCH 5/5] KVM: VMX: Always honor guest PAT on CPUs that support self-snoop From: Sean Christopherson To: Vitaly Kuznetsov Cc: Gerd Hoffmann , Paolo Bonzini , kvm@vger.kernel.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Kevin Tian , Yan Zhao , Yiwei Zhang , Lai Jiangshan , "Paul E. McKenney" , Josh Triplett Content-Type: text/plain; charset="us-ascii" On Fri, Aug 30, 2024, Vitaly Kuznetsov wrote: > Gerd Hoffmann writes: > > >> Necroposting! > >> > >> Turns out that this change broke "bochs-display" driver in QEMU even > >> when the guest is modern (don't ask me 'who the hell uses bochs for > >> modern guests', it was basically a configuration error :-). E.g: > > > > qemu stdvga (the default display device) is affected too. > > > > So far, I was only able to verify that the issue has nothing to do with > OVMF and multi-vcpu, it reproduces very well with > > $ qemu-kvm -machine q35,accel=kvm,kernel-irqchip=split -name guest=c10s > -cpu host -smp 1 -m 16384 -drive file=/var/lib/libvirt/images/c10s-bios.qcow2,if=none,id=drive-ide0-0-0 > -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 > -vnc :0 -device VGA -monitor stdio --no-reboot > > Comparing traces of working and broken cases, I couldn't find anything > suspicious but I may had missed something of course. For now, it seems > like a userspace misbehavior resulting in a segfault. Guest userspace?