From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 5035C370AD2 for ; Thu, 11 Jun 2026 07:53:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781164397; cv=none; b=AQlhig65d6shIuOKeNFoTq/rN5nDCcGgMxtYvWn+xrDmNWqMcM7/WnuNf6x14UH8N1NgVKW8bAmUS0Xy6MS5QxDrYxGeYTS12JiLKHUoNdOsRufIaFxoMzQv0JgB8xith1+s4TkfhrjSkmdLU2s0UhD7g/U95vdyUHDTsR7geg4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781164397; c=relaxed/simple; bh=9qwpK8h4o/+oTREsihjk9tvq/Nx0hsOrLCz6qNBCJuE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Pj/u7MyGAcubJk7USQNyTMGBnW4bleF6Dmn5iEgnNW7THtHSGw9l+5iV35MAP3HktP6Om7B9xBQVXlomIJGOb+jb3jVYWdVY+9p5pR/dcqVF/hZbJxQVjUkXSsWWvxVsOlxtaXYN4448+45ikkZKmK5FtxznDXcb8zu/TZaVYHI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=gtZgEWxo; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="gtZgEWxo" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=+9UMft+R27BIF5q3UlLAfJRKMwaWN46+3ChhDZoJpuA=; b=gtZgEWxolBfNzziG1zT4e64dBz 4RgbJkmeXiCS3cwmdhnGux1bkknCmpL1dsynJHvlYW7jKSnkOPDkPWKzM67/pood7LsHxOjn1a159 wTDvgy/5AFliO5L2K762/rWSiAepGLrzbDpZlGF6/TyfqUNkW1E3sOK+JH0yjCbetPjGXouCYV6he 9rh5i6W/tGtIsvl1Qqh33N3es4pKL0QI5sJiOfz65Rj43NNxDdmOLZYvPS79D0K4TcDM4kfI8QP9Q x41H56gOWN0U5AA+6IbAxoRYpp8cf5RPouiw5w7z0cVTJ4kRarX8Hhtns+seQF4jiMsI49r9n2mU/ /8rcIS4w==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.2 #2 (Red Hat Linux)) id 1wXaDw-00000004uxP-1OK4; Thu, 11 Jun 2026 07:53:12 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 5A403301A42; Thu, 11 Jun 2026 09:53:11 +0200 (CEST) Date: Thu, 11 Jun 2026 09:53:11 +0200 From: Peter Zijlstra To: Borislav Petkov Cc: Ronan Pigott , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: UMIP and clearcpuid= Message-ID: <20260611075311.GH48970@noisy.programming.kicks-ass.net> References: <20260610200054.GDainCdpF585khK77w@fat_crate.local> <3868008f140c843f4443b79d800dba5456df174a@rjp.ie> <20260610235501.GGain5VbwcvpUwCxiw@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=us-ascii Content-Disposition: inline In-Reply-To: <20260610235501.GGain5VbwcvpUwCxiw@fat_crate.local> On Wed, Jun 10, 2026 at 04:55:01PM -0700, Borislav Petkov wrote: > On Wed, Jun 10, 2026 at 08:41:02PM +0000, Ronan Pigott wrote: > > My use case is playing Windows video games via Wine. For whatever reason, > > they like to use these instructions: > > > > $ journalctl -b -g umip -o cat --since=-5m > > umip_printk: 117 callbacks suppressed > > umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: SGDT instruction cannot be used by applications. > > umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: For now, expensive software emulation returns the result. > > umip: StreetFighter6.[3837] ip:15f523f4d sp:524fec20: SGDT instruction cannot be used by applications. > > umip: StreetFighter6.[3837] ip:15f523f4d sp:524fec20: For now, expensive software emulation returns the result. > > umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: SGDT instruction cannot be used by applications. > > > > I don't think I benefit from the UMIP protection or the emulation, so I'd > > Question is, do you benefit from disabling the UMIP emulation. Any noticeable > game performance increase? > > > rather just disable it. clearcpuid still works, but results in a tainted > > kernel etc: > > > > kernel: clearcpuid: force-disabling CPU feature flag: umip > > kernel: !!! setcpuid=/clearcpuid= in use, this is for TESTING ONLY, may break things horribly. Tainting kernel. > > Right, I don't think a tainted kernel would be a problem but yeah... > > I still think that it would make sense to issue a big fat warning when > disabling UMIP so that people know. > > > so I think a umip=no flag as originally proposed could be preferable. Would > > that be acceptable? > > umip=disable or umip=off > > I guess. > > Other than that, I guess that's a valid use case I'd say. Let's see what the > others think. So my own game box also has this; aside from the dmesg spam, there was one game that just plain didn't run. I forgot what it was, but I'm sure it was related to some dodgy DRM thing. It is really annoying having to disable UMIP though, its bugged me, just not enough to ever actually do anything about it.