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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rioq9-0000000D3Cq-1PKl; Sat, 09 Mar 2024 05:01:45 +0000 Date: Sat, 9 Mar 2024 05:01:45 +0000 From: Matthew Wilcox To: "Gowans, James" Cc: "seanjc@google.com" , "akpm@linux-foundation.org" , "Roy, Patrick" , "chao.p.peng@linux.intel.com" , "Manwaring, Derek" , "rppt@kernel.org" , "pbonzini@redhat.com" , "Woodhouse, David" , "Kalyazin, Nikita" , "lstoakes@gmail.com" , "Liam.Howlett@oracle.com" , "linux-mm@kvack.org" , "qemu-devel@nongnu.org" , "kirill.shutemov@linux.intel.com" , "vbabka@suse.cz" , "mst@redhat.com" , "somlo@cmu.edu" , "Graf (AWS), Alexander" , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" Subject: Re: Unmapping KVM Guest Memory from Host Kernel Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 199A44000E X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 1cqzsbq41kdiqtm49rgd6jhmmeofhs4y X-HE-Tag: 1709960512-998424 X-HE-Meta: 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 dEltFl2i Y15MUU4m5IbKJbdyvJRuPGUDeAC/8Vofbmc0/cANg43bDufDpfSDRK9yNO35dSWnKAXw9lJ/UJ+iSEITZblEV9e8AxfEXYH0iV1L9VpXrrhN4mmb50YiEOur91Q9rL9J41TsepeFXP6Wyuq7MSN9bZBCmp8AD1JmQ7cmqTIOMugbUQl7KQz0VO+cxByqw3uGeF/qV8Un/k6EgOQ8= 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 Fri, Mar 08, 2024 at 03:50:05PM +0000, Gowans, James wrote: > Currently when using anonymous memory for KVM guest RAM, the memory all > remains mapped into the kernel direct map. We are looking at options to > get KVM guest memory out of the kernel’s direct map as a principled > approach to mitigating speculative execution issues in the host kernel. > Our goal is to more completely address the class of issues whose leak > origin is categorized as "Mapped memory" [1]. One of the things that is holding Linux back is the inability to do I/O to memory which is not part of memmap. _So Much_ of our infrastructure is based on having a struct page available to stick into an sglist, bio, skb_frag, or whatever. The solution to this is to move to a (phys_addr, length) tuple instead of (page, offset, len) tuple. I call this "phyr" and I've written about it before. I'm not working on this as I have quite enough to do with the folio work, but I hope somebody works on it before I get time to.