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Shutemov" To: Michael Roth Cc: Chao Peng , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , tabba@google.com, mhocko@suse.com, Muchun Song , wei.w.wang@intel.com Subject: Re: [PATCH v9 1/8] mm: Introduce memfd_restricted system call to create restricted user memory Message-ID: <20221102211404.l5whyif3j3k67fv2@box.shutemov.name> References: <20221025151344.3784230-1-chao.p.peng@linux.intel.com> <20221025151344.3784230-2-chao.p.peng@linux.intel.com> <20221031174738.fklhlia5fmaiinpe@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221031174738.fklhlia5fmaiinpe@amd.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667423655; a=rsa-sha256; cv=none; b=8I6+lf6o/VWvQpUXp74YHURiOTzBgpuZ0ESpi+Aaf+P2z8mFZEcW1v07iHY5sCP0xYlbEb 2vSfPA/+FnvzB+X1ABaO1H0hsgT3OFRb1L3i33z643uS4ZmfTo8VzMOIq3ZICQDKhWZygD d2tezxddiGKLal0sDMzTwf2FrRpI/GE= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm2 header.b=Ky05TEuW; dkim=pass header.d=messagingengine.com header.s=fm3 header.b=kXuKgSJS; spf=pass (imf04.hostedemail.com: domain of kirill@shutemov.name designates 64.147.123.27 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1667423655; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=yaz7HB+tA0RP33F5tMpk/jLLItyrZaFvVEGA2nFMTHI=; b=PnHYcot7XN+tEXkrxlZinLS5Bb3LFl75KFWWmJlrkVBI2N4/8UK3st8eQkUyf6QCpXOk9c P27N8Ztj24SAeR8ek3tuuHdcB/5RzuFGSLa63Jl8PlQFkJFJhRS2mR2GQZb1zBoEdgadTe kzjg3c+4gLSvvBUhVgvtnW+HnLZv6vs= X-Stat-Signature: e7but4t6mbhjt7idpuocqpysnaxe73s8 X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 304C040007 Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm2 header.b=Ky05TEuW; dkim=pass header.d=messagingengine.com header.s=fm3 header.b=kXuKgSJS; spf=pass (imf04.hostedemail.com: domain of kirill@shutemov.name designates 64.147.123.27 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none X-HE-Tag: 1667423654-79465 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: On Mon, Oct 31, 2022 at 12:47:38PM -0500, Michael Roth wrote: > > In v8 there was some discussion about potentially passing the page/folio > and order as part of the invalidation callback, I ended up needing > something similar for SEV-SNP, and think it might make sense for other > platforms. This main reasoning is: > > 1) restoring kernel directmap: > > Currently SNP (and I believe TDX) need to either split or remove kernel > direct mappings for restricted PFNs, since there is no guarantee that > other PFNs within a 2MB range won't be used for non-restricted > (which will cause an RMP #PF in the case of SNP since the 2MB > mapping overlaps with guest-owned pages) That's news to me. Where the restriction for SNP comes from? There's no such limitation on TDX side AFAIK? Could you point me to relevant documentation if there's any? -- Kiryl Shutsemau / Kirill A. Shutemov