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Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jkttA-0003xc-97; Mon, 15 Jun 2020 18:31:21 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 5D9C03003E1; Mon, 15 Jun 2020 20:31:16 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4B487203B815D; Mon, 15 Jun 2020 20:31:16 +0200 (CEST) Date: Mon, 15 Jun 2020 20:31:16 +0200 From: Peter Zijlstra To: Fenghua Yu Subject: Re: [PATCH v2 12/12] x86/traps: Fix up invalid PASID Message-ID: <20200615183116.GD2531@hirez.programming.kicks-ass.net> References: <1592008893-9388-1-git-send-email-fenghua.yu@intel.com> <1592008893-9388-13-git-send-email-fenghua.yu@intel.com> <20200615075649.GK2497@hirez.programming.kicks-ass.net> <20200615154854.GB13792@romley-ivt3.sc.intel.com> <20200615160357.GA2531@hirez.programming.kicks-ass.net> <20200615181259.GC13792@romley-ivt3.sc.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200615181259.GC13792@romley-ivt3.sc.intel.com> Cc: Dave Hansen , H Peter Anvin , Dave Jiang , Ashok Raj , x86 , amd-gfx , Ingo Molnar , Ravi V Shankar , Yu-cheng Yu , Andrew Donnellan , Borislav Petkov , Thomas Gleixner , Tony Luck , linuxppc-dev , Felix Kuehling , linux-kernel , iommu@lists.linux-foundation.org, Jacob Jun Pan , Frederic Barrat , David Woodhouse X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Mon, Jun 15, 2020 at 11:12:59AM -0700, Fenghua Yu wrote: > > I don't get why you need a rdmsr here, or why not having one would > > require a TIF flag. Is that because this MSR is XSAVE/XRSTOR managed? > > My concern is TIF flags are precious (only 3 slots available). Defining > a new TIF flag may be not worth it while rdmsr() can check if PASID > is valid in the MSR. And performance here might not be a big issue > in #GP. > > But if you think using TIF flag is better, I can define a new TIF flag > and maintain it per thread (init 0 when clone()/fork(), set 1 in fixup()). > Then we can avoid using rdmsr() to check valid PASID in the MSR. WHY ?!?! What do you need a TIF flag for? _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu