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[92.26.98.202]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a6d1188247sm3046998f8f.76.2025.06.20.15.04.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Jun 2025 15:04:55 -0700 (PDT) Message-ID: <1aa5fb31-ce23-4c9f-ba1b-d5dc93402209@citrix.com> Date: Fri, 20 Jun 2025 23:04:53 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: dave.hansen@intel.com Cc: acme@redhat.com, aik@amd.com, akpm@linux-foundation.org, alexander.shishkin@linux.intel.com, ardb@kernel.org, ast@kernel.org, bp@alien8.de, brijesh.singh@amd.com, changbin.du@huawei.com, christophe.leroy@csgroup.eu, corbet@lwn.net, daniel.sneddon@linux.intel.com, dave.hansen@linux.intel.com, ebiggers@google.com, geert+renesas@glider.be, houtao1@huawei.com, hpa@zytor.com, jgg@ziepe.ca, jgross@suse.com, jpoimboe@kernel.org, kai.huang@intel.com, kees@kernel.org, kirill.shutemov@linux.intel.com, leitao@debian.org, linux-doc@vger.kernel.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux@rasmusvillemoes.dk, luto@kernel.org, mcgrof@kernel.org, mhiramat@kernel.org, michael.roth@amd.com, mingo@kernel.org, mingo@redhat.com, namhyung@kernel.org, paulmck@kernel.org, pawan.kumar.gupta@linux.intel.com, peterz@infradead.org, rick.p.edgecombe@intel.com, rppt@kernel.org, sandipan.das@amd.com, shijie@os.amperecomputing.com, sohil.mehta@intel.com, tglx@linutronix.de, tj@kernel.org, tony.luck@intel.com, vegard.nossum@oracle.com, x86@kernel.org, xin3.li@intel.com, xiongwei.song@windriver.com, ytcoode@gmail.com References: <61af62d9-4cd0-485f-8f0c-2da981f52695@intel.com> Subject: Re: [PATCHv6 00/16] x86: Enable Linear Address Space Separation support Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 64A6B80008 X-Stat-Signature: rk448i1c9u53qhp8a4a7mzpuigd9g6cx X-HE-Tag: 1750457097-891442 X-HE-Meta: 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 uZdt92oc 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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: List-Subscribe: List-Unsubscribe: > Most of the cover letter here reads like an Intel whitepaper. That's not > the worst thing in the world, but I think it glosses over one very > important point: > > Had it been available, LASS alone would have mitigated Meltdown. > > Could we say this up front in a prominent place, please? I'm going to nitpick. :) Yes, LASS would have made Meltdown a far less major problem than it was, but I don't think that phrasing is fair.  As I recall, LASS was literally invented as a "what would have been useful?" exercise in the wake of Meltdown. However, a less well known/researched area of Meltdown, which would not be addressed by LASS, is the ability to pend stores to read-only memory and proceed with the expectation that they'll success. Other things which would have helped would have been PKS (and this *was* asked for ahead of Skylake launching...) The other important thing about LASS is that it does cut off a whole class of sidechannels.  This halts definitely-rogue speculation, but is useful for non-speculative security too. ~Andrew