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X-IronPort-AV: E=McAfee;i="6600,9927,10955"; a="13410035" X-IronPort-AV: E=Sophos;i="6.05,199,1701158400"; d="scan'208";a="13410035" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmvoesa102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Jan 2024 08:21:14 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10955"; a="1031027297" X-IronPort-AV: E=Sophos;i="6.05,199,1701158400"; d="scan'208";a="1031027297" Received: from aegarcia-mobl1.amr.corp.intel.com (HELO [10.212.31.16]) ([10.212.31.16]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Jan 2024 08:21:11 -0800 Message-ID: <6ecc4517-9a4f-4d7e-a630-2b8357b7be05@intel.com> Date: Tue, 16 Jan 2024 08:21:09 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map when adding them to the RMP table Content-Language: en-US To: Borislav Petkov Cc: Michael Roth , x86@kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, peterz@infradead.org, srinivas.pandruvada@linux.intel.com, rientjes@google.com, tobin@ibm.com, vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, pankaj.gupta@amd.com, liam.merwick@oracle.com, zhi.a.wang@intel.com, Brijesh Singh References: <20231230161954.569267-1-michael.roth@amd.com> <20231230161954.569267-12-michael.roth@amd.com> <20240115090948.GBZaT2XKw00PokD-WJ@fat_crate.local> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: ndrbicx3bt7rhrc5rd41jpqkjrnw6gtz X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5D9ED40002 X-HE-Tag: 1705422077-261466 X-HE-Meta: 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 4aee/1ml XXYws880kGzYjV1V+AhvyAsZKGteRkeJTiNe/7SZfiuSBsgQF7FnIED7u7v+jA0hkn//tQpvjx3LfJPQ68vhJs3JGWSbIbDB0aJ1XUy0FTCVcQsoV9nX6W2imB1uRHdI5oraX+Q3jG5F+tpqs6rmkoeiSm4AQEbEgP+CZcNwx4v9niQHXx9FGaITB2OmYt1uk6QjKN/lhFUbMSVPmZm3RAbvMRaixt/501ZBd5uatFxxQb9rVYk8XxAHmAhhGfIQQEE41PCKaFK/E8ldI1FUvd9oaHU0pZPVRVgVAn6nombsa7RKHu1tZlQKoyjHZ0xfZw96p 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: List-Subscribe: List-Unsubscribe: On 1/15/24 01:09, Borislav Petkov wrote: > On Fri, Jan 12, 2024 at 12:00:01PM -0800, Dave Hansen wrote: >> I thought we agreed long ago to just demote the whole direct map to 4k >> on kernels that might need to act as SEV-SNP hosts. That should be step >> one and this can be discussed as an optimization later. > > Do we have a link to that agreement somewhere? I seem to be remembering it wrong. I have some memory of disabling 2M mappings in the same spots that debug_pagealloc_enabled() does, but I must have hallucinated it. > https://lore.kernel.org/lkml/535400b4-0593-a7ca-1548-532ee1fefbd7@intel.com/ The original approach tried to fix up the page faults by doing the demotion there and didn't seem to work with hugetlbfs at all. > I'd like to read why we agreed. And looking at Mike's talk: > https://lwn.net/Articles/931406/ - what do we wanna do in general with > the direct map granularity? I think fracturing it is much less of a problem than we once thought it was. There are _definitely_ people that will pay the cost for added security. The problem will be the first time someone sees a regression when their direct-map-fracturing kernel feature (secret pages, SNP host, etc...) collides with some workload that's sensitive to kernel TLB pressure.