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Shutemov" , Jacob Pan , Ashok Raj , "Kirill A. Shutemov" , Ashok Raj , Dave Hansen , Andy Lutomirski , Peter Zijlstra , x86@kernel.org, Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Alexander Potapenko , Taras Madan , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joerg Roedel , jacob.jun.pan@linux.intel.com Subject: Re: [PATCHv8 00/11] Linear Address Masking enabling Message-ID: <20220920113742.277ac497@jacob-builder> In-Reply-To: References: <20220914144518.46rhhyh7zmxieozs@box.shutemov.name> <20220914151818.uupzpyd333qnnmlt@box.shutemov.name> <20220914154532.mmxfsr7eadgnxt3s@box.shutemov.name> <20220914165116.24f82d74@jacob-builder> <20220915090135.fpeokbokkdljv7rw@box.shutemov.name> <20220915172858.pl62a5w3m5binxrk@box.shutemov.name> <15741fdf-68b6-bd32-b0c2-63fde3bb0db2@intel.com> Organization: OTC X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663699058; a=rsa-sha256; cv=none; b=7qC6NPyUgbA0aavnyLOX6DmuLriOdJ2i+it09yg2Yc9D9fcjfGX9xEkuU0nXzS0Ivgqvnn lJEeDq/0eqG1vusFGDFVx2PJwoOl0Oo3WGHHhQzVlO46o0H+vFIdj7TklGOdSeS5tHcUrl ocZCfRVaotsbvkUpmSv7kkHDSdYavyA= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=MNvlVjDc; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none); spf=none (imf21.hostedemail.com: domain of jacob.jun.pan@linux.intel.com has no SPF policy when checking 192.55.52.120) smtp.mailfrom=jacob.jun.pan@linux.intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663699058; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=2GFWGGrKGBa5F7dNKu2gGRRpNEqVW9ty/j8I0SRCClM=; b=s3/K5Fh63V8lu0pVAn4vvekxkmr54kk0YTbdvU+TYUaed7dps+oM4gQj7hsA+kPjyecbtk B51zFovST8lTGWqbR105+wc+36/mKvuA8fQT/IFczbcQCqCGLbSnv3/s0NS2Cu/+FzgSQf dplAzR0q4wHQl36ON9nCSYtAJwV40lQ= X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 154941C000E X-Stat-Signature: uz95hapsc7kd4oybhqat6pcypqdtar8t Authentication-Results: imf21.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=MNvlVjDc; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none); spf=none (imf21.hostedemail.com: domain of jacob.jun.pan@linux.intel.com has no SPF policy when checking 192.55.52.120) smtp.mailfrom=jacob.jun.pan@linux.intel.com X-Rspam-User: X-HE-Tag: 1663699057-327383 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Jason, On Tue, 20 Sep 2022 13:27:27 -0300, Jason Gunthorpe wrote: > On Tue, Sep 20, 2022 at 09:06:32AM -0700, Dave Hansen wrote: > > On 9/20/22 06:14, Jason Gunthorpe wrote: > > > For this I would rather have a function that queries the format of the > > > page table under the mm_struct and we have enum values like > > > INTEL_NORMAL and INTEL_LAM as possible values. > > > > > > The iommu driver will block incompatible page table formats, and when > > > it starts up it should assert something that blocks changing the > > > format. > > > > That doesn't sound too bad. Except, please don't call it a "page table > > format". The format of the page tables does not change with LAM. It's > > entirely how the CPU interprets addresses that changes. > > Sure it does. The rules for how the page table is walked change. The > actual bits stored in memory might not be different, but that doesn't > mean the format didn't change. If it didn't change we wouldn't have an > incompatibility with the IOMMU HW walker. There are many CPU-IOMMU compatibility checks before we do for SVA,e.g. we check paging mode in sva_bind. We are delegating these checks in arch/platform code. So why can't we let arch code decide how to convey mm-IOMMU SVA compatibility? let it be a flag ( as in this patch) or some callback. Perhaps a more descriptive name s/arch_can_alloc_pasid(mm)/arch_can_support_sva(mm)/ is all we disagreeing :) Thanks, Jacob