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[209.85.208.44]) by smtp.gmail.com with ESMTPSA id v4-20020a17090690c400b0099b921de301sm8102728ejw.159.2023.09.19.11.50.06 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 Sep 2023 11:50:06 -0700 (PDT) Received: by mail-ed1-f44.google.com with SMTP id 4fb4d7f45d1cf-530a6cbbb47so5181796a12.0 for ; Tue, 19 Sep 2023 11:50:06 -0700 (PDT) X-Received: by 2002:a50:ee14:0:b0:530:d8df:afaa with SMTP id g20-20020a50ee14000000b00530d8dfafaamr219079eds.41.1695149405833; Tue, 19 Sep 2023 11:50:05 -0700 (PDT) MIME-Version: 1.0 References: <20230915105933.495735-1-matteorizzo@google.com> <7a4f5128-28fd-3c5f-34c2-1c34f4448174@intel.com> <1d7573c0-ebbc-6ed2-f152-1045eb0542f9@os.amperecomputing.com> In-Reply-To: From: Linus Torvalds Date: Tue, 19 Sep 2023 11:49:48 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 00/14] Prevent cross-cache attacks in the SLUB allocator To: Matteo Rizzo Cc: Ingo Molnar , "Lameter, Christopher" , Dave Hansen , penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, corbet@lwn.net, luto@kernel.org, peterz@infradead.org, jannh@google.com, evn@google.com, poprdi@google.com, jordyzomer@google.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: ozkj8iakycquj5y4759qwxxc3569y3w9 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: F3317140017 X-Rspam-User: X-HE-Tag: 1695149408-610719 X-HE-Meta: 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 uLKB5obD 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 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 Tue, 19 Sept 2023 at 08:48, Matteo Rizzo wrote: > > On Mon, 18 Sept 2023 at 20:05, Linus Torvalds > wrote: > > > > ... and equally importantly, what about DMA? > > I'm not exactly sure what you mean by this, I don't think this should > affect the performance of DMA. I was more worried about just basic correctness. We've traditionally had a lot of issues with using virtual addresses for dma, simply because we've got random drivers, and I'm not entirely convinced that your "virt_to_phys()" update will catch it all. IOW, even on x86-64 - which is hopefully better than most architectures because it already has that double mapping issue - we have things like unsigned long paddr = (unsigned long)vaddr - __PAGE_OFFSET; in other places than just the __phys_addr() code. The one place I grepped for looks to be just boot-time AMD memory encryption, so wouldn't be any slab allocation, but ... Linus