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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id d13-20020a17090ae28d00b00233e52b7797sm941662pjz.44.2023.02.19.12.48.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 19 Feb 2023 12:48:20 -0800 (PST) Message-ID: <63f28b14.170a0220.8cbeb.12e3@mx.google.com> X-Google-Original-Message-ID: <202302191248.@keescook> Date: Sun, 19 Feb 2023 12:48:19 -0800 From: Kees Cook To: Rick Edgecombe Cc: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, david@redhat.com, debug@rivosinc.com Subject: Re: [PATCH v6 38/41] x86/fpu: Add helper for initing features References: <20230218211433.26859-1-rick.p.edgecombe@intel.com> <20230218211433.26859-39-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230218211433.26859-39-rick.p.edgecombe@intel.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: F112712000F X-Stat-Signature: u3iohea37k47dbepabmmmompyficwdam X-HE-Tag: 1676839701-161749 X-HE-Meta: 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 ci03UDwH 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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 Sat, Feb 18, 2023 at 01:14:30PM -0800, Rick Edgecombe wrote: > If an xfeature is saved in a buffer, the xfeature's bit will be set in > xsave->header.xfeatures. The CPU may opt to not save the xfeature if it > is in it's init state. In this case the xfeature buffer address cannot > be retrieved with get_xsave_addr(). > > Future patches will need to handle the case of writing to an xfeature > that may not be saved. So provide helpers to init an xfeature in an > xsave buffer. > > This could of course be done directly by reaching into the xsave buffer, > however this would not be robust against future changes to optimize the > xsave buffer by compacting it. In that case the xsave buffer would need > to be re-arranged as well. So the logic properly belongs encapsulated > in a helper where the logic can be unified. > > Tested-by: Pengfei Xu > Tested-by: John Allen > Signed-off-by: Rick Edgecombe Reviewed-by: Kees Cook -- Kees Cook