From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (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 BDDBD33B96F for ; Fri, 31 Oct 2025 11:30:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761910258; cv=none; b=cLs3TTSBtf7BO+bPwenT38qTnNDOdJTY1H41DqFuKFkC2/dFzZiqJxFxOYDFe4nGIGKvCuJKh18xMe687+U9/1eQSHOW5q+zImt6P8P/3d+iYZTdYzR7K4tegCZ8xyyQ0yCdeoQPPCVm0Z7+WqZWxtYJ1hXvY0zJA3o68XShUt4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761910258; c=relaxed/simple; bh=xb3z6RRv9FWBgbpoNB+f0HdOZ7ja5DXI4nWbdCPpE58=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ERAuwIVkNiL5jzEbVFX/lt/oxE0gj+azQiGCxTE8Nb2leazE2eJvs7jMUosqXtb5nPynU76qN/dU4GV/XPiTU1+HbH/voGmuG0Z4LWxX97YF5OChDFzOsmypL18BoLMHQNHVGQONUSJFTWkhr0tX+dFLrm6wL2lDc2mpe6tyFto= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=O56zN/Rr; arc=none smtp.client-ip=209.85.128.73 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--jackmanb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="O56zN/Rr" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-475e032d81bso18644185e9.3 for ; Fri, 31 Oct 2025 04:30:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1761910255; x=1762515055; 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=f5LhUGa1olQ3GKY/+89Hs0L3mppFiQpo0PHzSoy/D1E=; b=O56zN/RrFQWbNCswqdl5WyNgUtp5F1+s379ohxy8R/H3q809kGRuH4Odd72qIfIaPb IaIifsjToig37mI6syZAoPgag81dihlMNod644lxpB7OST92lkExroM9XxXMXzj1hbBI /KbE4LHR2/KTFYP8YTjt5ayNj1s3fJ+EBM/vEJtI5aJpnMKwR+gdQThiu/wT/L+SU7uj N7Nm7EuT/td25i87+4e/1ihWjak2eprN/Xq1WohoXr+w1Zq96xZaMgg2+n4PBQfgbR9O GTvp+lEVa4V4bBWw1z4QkOumeRM0EelNWOILER+ApTq+owi7z3rqcGFXKpMUyCnZOYY1 bcaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761910255; x=1762515055; 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=f5LhUGa1olQ3GKY/+89Hs0L3mppFiQpo0PHzSoy/D1E=; b=KbV8xmu04RcUvLBGOtjflY9aPqRVipGxZfxCj5UF+NVDXYbfm2vshCI1qrMWGhBnxn Lk3wXHmpPE5HEqSsaZ3o7SLC82Adb6GKax8pMU22dxSpaiPPt6J1A9EXtwWI2zJHFYo0 VngTHhs5Gk+fiMFmHkeBEgYo7nKLksONUzk5CGiA6zCbM5ld6TIU00JWYVdqIC9odfu5 fQfza5Gpj9sufTCfz/7I4/N5hxfgSurq5hqXccExKa+U7Zff6Afd91JvQYmD5Wnnexo0 8YkEJiK73HWpamDIhj0zIVQgH0zidl4E24Z32QIa40gMLt8wJHpnxJUMEFJNBSuz4wdA WjXw== X-Forwarded-Encrypted: i=1; AJvYcCV8KWFFyhB7s7QwhS+tu60r+5Y3+nZ881YBifbw7sSqRe6MEWJlChQbv9syn/2NhSldkAQa8XuZ9dAeVmc=@vger.kernel.org X-Gm-Message-State: AOJu0Yz9uSrP6gLAzPHU4IYBG/5gqXDSr9EkdpTnZoAuCGVbAjA/j5OL V6k0TQF/610EoWCa47ehUO4pGUsU3SM5UzkTeXpiLTNmDjjbvVngL3tO9gXbLyr75Iu4oy2ADjN 2uNT3dmy6w7EIUw== X-Google-Smtp-Source: AGHT+IGsaBJIkQ/y8I03wvIhCvj64lg46pEHivGFWKZTeovvbi13vTifrl6UEKclPzTqf3k83Nt11P3xJ27+8A== X-Received: from wmvz2.prod.google.com ([2002:a05:600d:6282:b0:477:d21:4a92]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:41d2:b0:429:b21e:49b2 with SMTP id ffacd0b85a97d-429bd6ac0a0mr2563121f8f.51.1761910255127; Fri, 31 Oct 2025 04:30:55 -0700 (PDT) Date: Fri, 31 Oct 2025 11:30:54 +0000 In-Reply-To: <20251031003040.3491385-2-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251031003040.3491385-1-seanjc@google.com> <20251031003040.3491385-2-seanjc@google.com> X-Mailer: aerc 0.21.0 Message-ID: Subject: Re: [PATCH v4 1/8] x86/bugs: Use VM_CLEAR_CPU_BUFFERS in VMX as well From: Brendan Jackman To: Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Borislav Petkov , Peter Zijlstra , Josh Poimboeuf Cc: , , Pawan Gupta , Brendan Jackman Content-Type: text/plain; charset="UTF-8" Rewording my comments from: https://lore.kernel.org/all/20251029-verw-vm-v1-1-babf9b961519@linux.intel.com/ On Fri Oct 31, 2025 at 12:30 AM UTC, Sean Christopherson wrote: > From: Pawan Gupta > > TSA mitigation: > > d8010d4ba43e ("x86/bugs: Add a Transient Scheduler Attacks mitigation") > > introduced VM_CLEAR_CPU_BUFFERS for guests on AMD CPUs. Currently on Intel > CLEAR_CPU_BUFFERS is being used for guests which has a much broader scope > (kernel->user also). > > Make mitigations on Intel consistent with TSA. This would help handling the > guest-only mitigations better in future. > > Signed-off-by: Pawan Gupta > [sean: make CLEAR_CPU_BUF_VM mutually exclusive with the MMIO mitigation] > Signed-off-by: Sean Christopherson I think this is a clear improvement. Now that X86_FEATURE_CLEAR_CPU_BUF has a clear scope, can we also update the comment on its definition in cpufeatures.h? I.e. say that it's specifically about exit to user. This also seems like a good moment to update the comment on verw_clear_cpu_buf_mitigation_selected to mention the _VM flag too. Also, where we set vmx->disable_fb_clear in vmx_update_fb_clear_dis(), it still refers to X86_FEATURE_CLEAR_CPU_BUF, is that wrong?