From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 11E2D19F464; Thu, 6 Feb 2025 18:58:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738868300; cv=none; b=jCWil5almbAB4oPkcS8nEsOG6uAVAMlxdq1BxC1C5yX8JPnxJKg3R3DUzhP+BCi/Yo/QPr52eCSKQ5SQ28TpIU9tQ/SfrixMbVLPglyyCnjRvWOwlh0x7VFUKLPvlJ1oASWFdm5Tkp8hJ7oigqnSybv/sJ1yBrIjEnChEyBXfKI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738868300; c=relaxed/simple; bh=8hRgzL1B/JGnaj5lF5A8Ys2U6fexDb2aSBDK4P2Stao=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=qFZC3WwgkT35B9mI5IJtagsXBODEF+d0KPBxnhS7T7JMXLBixzC+ftQTtDzLK9Wc28olGtFdrLZxtx7AHNnAeAZL1zG8K3F7foO2RNl7ZgLAngfzvEaWdrX6yxMFvud2k0Il7mMryIyfiHa4iLDVohb0fkH6apZunQfBVeCzAic= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=casper.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=DTqh5v3h; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=casper.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DTqh5v3h" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=8hRgzL1B/JGnaj5lF5A8Ys2U6fexDb2aSBDK4P2Stao=; b=DTqh5v3htIu1J/SosHLdsX2eed kfNpsB6oSllRnmCM1JPv+UKBTtBCGrWGjukMYEawjLjeulO3J60YY7VhBRw/K/RyvjERs9vLJNk5x IiTH0heXGzrxwJXCo7T/qVxTdPRvT9up7i/SE5ejjC2h7eBase40iEO/BI8H0kxtI9Rp7TU5uFq95 lHn09wryqihJ977Zlbw3AlrxEeVC/X/MkjQ+KInQDN5x1R0ztav/nw8Owdm5bYIsMTVqlUbEiA3Iq pOfnXq6XhV6ExTpB/o6cKPWXOJso9ds97mKz56Ao1mLwiSZuEU7ACJzLJK9uib6NN5CDpnhMJN8J4 aoUF+WpA==; Received: from [54.239.6.187] (helo=freeip.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tg74m-00000006SPI-20Cb; Thu, 06 Feb 2025 18:58:12 +0000 Message-ID: <4410f771de905b8df18f7fc87fe5a034d1a57a7b.camel@infradead.org> Subject: Re: [PATCH 1/5] KVM: x86/xen: Restrict hypercall MSR to unofficial synthetic range From: David Woodhouse To: Sean Christopherson Cc: Paolo Bonzini , Paul Durrant , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+cdeaeec70992eca2d920@syzkaller.appspotmail.com, Joao Martins Date: Thu, 06 Feb 2025 18:58:11 +0000 In-Reply-To: References: <20250201011400.669483-1-seanjc@google.com> <20250201011400.669483-2-seanjc@google.com> <43f702b383fb99d435f2cdb8ef35cc1449fe6c23.camel@infradead.org> <48FAD370-09F1-47AA-8892-8BE29DC8A949@infradead.org> <85f8aaea4cb5918cef92309c8c1c26fc7fd113b8.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-q9u42lPy1Sfm6Owvy46A" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html --=-q9u42lPy1Sfm6Owvy46A Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2025-02-05 at 11:20 -0800, Sean Christopherson wrote: > On Wed, Feb 05, 2025, David Woodhouse wrote: > > On Wed, 2025-02-05 at 16:18 +0000, David Woodhouse wrote: > > >=20 > > > > Oh!=C2=A0 It doesn't help KVM avoid breaking userspace, but a way f= or QEMU to avoid a > > > > future collision would be to have QEMU start at 0x40000200 when Hyp= er-V is enabled, > > > > but then use KVM_GET_MSR_INDEX_LIST to detect a collision with KVM = Hyper-V, e.g. > > > > increment the index until an available index is found (with sanity = checks and whatnot). > > >=20 > > > Makes sense. I think that's a third separate patch, yes? > >=20 > > To be clear, I think I mean a third patch which further restricts > > kvm_xen_hvm_config() to disallow indices for which > > kvm_is_advertised_msr() returns true? > >=20 > > We could roll that into your original patch instead, if you prefer. >=20 > Nah, I like the idea of separate patch. Helpfully, kvm_is_advertised_msr() doesn't actually return true for MSR_IA32_XSS. Is that a bug? And kvm_vcpu_reset() attempts to set MSR_IA32_XSS even if the guest doesn't have X86_FEATURE_XSAVES. 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