From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.alien8.de (mail.alien8.de [65.109.113.108]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8682D24A05B for ; Mon, 18 Aug 2025 14:31:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=65.109.113.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755527509; cv=none; b=SIQWulqVhB/eXFeiu4O1yDVQq3H4NPZ2s7EOl6zFqRMWEtcEzMABPsXh0uFDJ0iPM6fQGSDKiPI764xaR1iz6BJJ7XdhromScJBBX+6xKIII/VW2GdaZwSAGYrf+Vw09EE5BNrD4nbo6VRz9p/eLl8bYnrtQE3lFCEKZdB6MQsY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755527509; c=relaxed/simple; bh=H35AqFhE9vf8q6g0jToXYzEkYxqZTkp/ncpC7ZptQqk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bDBpH3k00ynzGTB+pqsQIHLnsutFA/65Qfl/xmUDMhmyi1ZQ+Hc7Pcr7AVCwP2d4xZQoH4VpufTdhhNvSeZj5RtQuPlemwtrkZL8AP1Jo+ftbJlDd9p7gBKXrFFFTsa8QBkqnAUzt3LgzeS9f+nTi5LuLPXnT4hRyvh3s000zMg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=alien8.de; spf=pass smtp.mailfrom=alien8.de; dkim=pass (4096-bit key) header.d=alien8.de header.i=@alien8.de header.b=FmBdDsJJ; arc=none smtp.client-ip=65.109.113.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=alien8.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=alien8.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (4096-bit key) header.d=alien8.de header.i=@alien8.de header.b="FmBdDsJJ" Received: from localhost (localhost.localdomain [127.0.0.1]) by mail.alien8.de (SuperMail on ZX Spectrum 128k) with ESMTP id 368F440E023B; Mon, 18 Aug 2025 14:31:44 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at mail.alien8.de Authentication-Results: mail.alien8.de (amavisd-new); dkim=pass (4096-bit key) header.d=alien8.de Received: from mail.alien8.de ([127.0.0.1]) by localhost (mail.alien8.de [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 2uyVxojAeshl; Mon, 18 Aug 2025 14:31:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=alien8; t=1755527498; bh=edxOOclTXrjoLplZzYIso8JyrxanTdeyvf0v0A9i2yY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FmBdDsJJEOm+9WAf5xQ9QfyVFfsbs+i52/hplurvwopZIobWwCjis+XbiohDPgpMj IpPcYKITwrtYRJ0KzLwXUe5+LgwSCaaWJXphN7gqy/d8jy2HlpP+GcvNuzyJGran+5 KsuqYjAcZ92v+StOnqj5hzSIYZOn1130/RFQcEiOXnpSckkKQS+qs+AneRdn9/v4/y 15440p3k2JuLg/lVxiCcnjGtLmfZa9zVGFYj1QMDB+l71yC2GlUMBz4MEN3qOfM/7B JEqb14reeN7UXLeH3h/aYtJxIromQamwYTLgLib8wm6jCUanIfkHL8rbfX7/FdFx/h rWtoQ/h95VupkGrxinhVRT0pUIn23WJwA9xvuSPfTTNmcye5EHKFtC5Yox1EFlXszf ezFsaXEEAq6Wt9uTm5n3D/pBKUWJUhnJ7b8YSvPvcz+K2Zr1jnbq77lc+KN6rRHHzB FTixN/Ma7zxr+rtCRxVWrUP3O7elU3xFwkVT5VswZAqL+XnZXCUnOK4QaHMAujXylZ +h5pTv2qOHOopHL1SNOwp/2ylorO/bpVjTpSDjX8Y84zODVW8nwtdCzUwbm/mPuJ1N ulwy1U8TaE6DCcKEDXW1YzgUCseG0DYyhWQ6E9fK6URc4+KmH01y6FxGSdFAKpoMKs Qei40JXVlOvcfHd0l73xLedw= Received: from zn.tnic (pd953092e.dip0.t-ipconnect.de [217.83.9.46]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature ECDSA (P-256) server-digest SHA256) (No client certificate requested) by mail.alien8.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id B63A140E0217; Mon, 18 Aug 2025 14:31:31 +0000 (UTC) Date: Mon, 18 Aug 2025 16:31:26 +0200 From: Borislav Petkov To: Sean Christopherson Cc: Mario Limonciello , Yazen Ghannam , x86@kernel.org, linux-kernel@vger.kernel.org, Libing He , David Arcari Subject: Re: [PATCH] x86/CPU/AMD: Ignore invalid reset reason value Message-ID: <20250818143126.GHaKM5PsVZPXwr5sPi@fat_crate.local> References: <27E487FE-EC8D-42AC-B259-F8A18776C802@alien8.de> <3cc16f7d-c650-43f2-b0ca-d99c427cd69b@amd.com> <20250725065009.GAaIMpIVgAKi0kMBVv@renoirsky.local> <20250815220436.GJaJ-u9FUVTmjyaaua@fat_crate.local> <20250816084218.GAaKBEaukeGa6b5UBj@fat_crate.local> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Mon, Aug 18, 2025 at 07:24:26AM -0700, Sean Christopherson wrote: > Most definitely not if the guest owner and host owner are not one and the same. > The example use case is where the platform owner is running one of _their_ kernels > in a VM, in which case that kernel probably does want to know why the platform > reboot. Except that can you control who uses that feature? If it ends up being used by a VM stack where the guest owner should not know the reboot reason, you've lost. > The same thing that guarantees hardware vendors adhere to specs: the desire to > get paid. So you're basically saying all HV vendors return -1 for an unimplemented register and we should be fine there? > And QEMU did return an error value, 0xffffffff, a.k.a. PCI Master Abort / PCIe > Unsupported Request. I would be amazed if any real world, general purpose VMM > did anything else for an MMIO access to an unknown/unsupported range. Ok, I guess we will know soon enough. :-) > Huh? Handle a read of all 0xffs as proposed in this patch, and this is unnecessary. I don't trust that all HVs will DTRT. But ok, I'll take your word for it. We can run with this and we'll know soon enough whether fishing out -1 is good enough. And then we'll have more fun. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette