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 754663C3458 for ; Mon, 8 Jun 2026 14:39:26 +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=1780929568; cv=none; b=O1QH/xEZRoq0N/M+HmQFTQR7GAFWltW1ghXF4kNxQZhCjWPAFJj+2eA8SG6QR0+eOAvVcZmoXtTtiNQX3DyN7g3U1kxkhjQSXAorjuSl53kf6IOuDl/8hQ3SKYE8tGh1QP8gRMnH/Og1mrerrId59qIRyWnYH238DjgH/29dLFQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780929568; c=relaxed/simple; bh=E5eo4Mo5EXDI09nFCk2QoBHOEU8AtPJhSqJe3US/6aE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XHnGGs39QEYocYmatuyUM7dw0oYMRhlM4EJdEFPzQKqxS02wWiErnFZLLofuXCqCIirJnFgcKL8Jk2i0/+m+pNHYZylLozSHCwiKYgjvFM3V6aW0FlzIVYD6Lkev35PMIwzqRFy+zfdFbRuJRRc+WE3AW8sGyKAKiEj6F6cWN5A= 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=WRhX2mqJ; 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="WRhX2mqJ" Received: from localhost (localhost.localdomain [127.0.0.1]) by mail.alien8.de (SuperMail on ZX Spectrum 128k) with ESMTP id 6CFFA40E0214; Mon, 8 Jun 2026 14:39:24 +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 YLoAt2fVcQaz; Mon, 8 Jun 2026 14:39:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=alien8; t=1780929550; bh=MJ007zwP0XOA/sjMoF44vGDsz82dDrw3p2u179aktcw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WRhX2mqJvMK1E3kVJuXWa/m6+XRABp0LPDozG3UUFqnPND/z0yzG17uZzQoJwihef dvU/8zeQ+pZyEGwW6ebL/8A4IYCn4pvNQCE0tK670z5nwQXepHAG8y0sHY+Z0DJ4Rv LFLQ9lO1B4LGw4K1TLefXcbRD/Yn7X2ripm0qRPJ2zGKfX6qzJQMvS1MBPji9OauUs viYSXoR9Q3w0Psaqg6g3C/TRBT2uHIwo+JCWbEJVbtlip8LAKMEu1nQSnSZ0fMsdBR j3vRUn8g5dmhpW2i5w6IPnhjlBzhaaFlh0zCHjL6wN4UOGX8EROgrRFGjdjcK6vZKP ZGGA3hyp4xr2z7e2NPA132icDrIY1tNUNklRLJZiXA39BYet3lyXx/I1LWutBFwDoy 2DuVecTiSltTG1ukrjfOC2d0M8QB3BtBLMynkDKW7xoMrR1Z8Y784MOR4kAYn2HWy5 s3YIL/+x1uigsgRwXITlQlH7LVVuW0ngBZknlgkWSbPsMLCDuha/KGs2hgoefv6jg4 h2oaF2KWD5KIa+rXw3zwzdNsCPKZI7Bc0Nk0gvDKANCdLZTbabzeWrV9rS4EXEY4yg SNbeUKo37d2OPbcoGcgcdxdMdLCyUqkOdbN0g+vbw/E/WmXGeqFfoJVHpt43FiqqqW EzxHxKTjW8N1Z7vvjT0h877w= Received: from stx.tnic (unknown [IPv6:2600:1700:38ca:c00::42]) (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 0698D40E0203; Mon, 8 Jun 2026 14:39:05 +0000 (UTC) Date: Mon, 8 Jun 2026 07:38:35 -0700 From: Borislav Petkov To: "H. Peter Anvin" Cc: Andrew Cooper , x86-ML , LKML Subject: Re: Save a WRMSR GS.base? Message-ID: <20260608143835.GAaibT6_Ypd2OzVkWD@fat_crate.local> References: <20260605042652.GBaiJQDMRcO_lO0Gig@fat_crate.local> <20260605043846.GCaiJS1iXH8A6Cb3Vy@fat_crate.local> <0F905129-3447-4173-A88B-98EAC8C18E4C@zytor.com> <1E2599FB-0A39-4637-B042-EE36DA224264@zytor.com> <2f297456-d6c6-4cc8-95d8-2dac6bea99ec@citrix.com> <20260605171711.GAaiMEl_CahU4oHpMk@fat_crate.local> <079850DB-52FE-4545-825F-E01E918B085D@zytor.com> 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: <079850DB-52FE-4545-825F-E01E918B085D@zytor.com> On Sun, Jun 07, 2026 at 11:46:34PM -0700, H. Peter Anvin wrote: > WRxSBASE does a 64-bit write, When REX.W. The SDM text is confusing: "If no REX.W prefix is used, the operand size is 32 bits; the upper 32 bits of the source register are ignored and upper 32 bits of the base address (for FS or GS) are cleared." Does this last part that GS is cleared, refer to when WRGSBASE is used with no REX.W or in general? > but for GS it would incorrectly address the kernel GS.base. What does that mean? Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette