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d=arm.com; s=foss; t=1794489248; bh=w1bnY+Ps4zITYTRUimdbVrN0cNHgFPf1y5ifSbYb950=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ir+GhsOFl4eXFwGT7DY570KXtbzdF31B+5y++WKx8y5Mt8D9PCavJtunWAPhq11FQ 3y9F+FQeN7oJYgE6McH1/9bBfmGxPdH3wzJzX2m8BupRfTjtvOMcJ34FftvP/WD6se sCtXi4bJ4nt0qiwC4fHQYnZSriQiUhYjZrdlfgEs= Date: Thu, 12 Nov 2026 13:14:01 +0000 From: Yeoreum Yun To: Mark Brown Cc: Kevin Brodsky , Yeoreum Yun , linux-hardening@vger.kernel.org, Andrew Morton , Ard Biesheuvel , Andy Lutomirski , Catalin Marinas , Dave Hansen , "David Hildenbrand (Arm)" , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linu Cherian , Linus Walleij , Marc Zyngier , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , =?iso-8859-1?Q?Pierre-Cl=E9ment?= Tosi , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Ira Weiny , Lorenzo Stoakes , Thomas Gleixner Subject: Re: [PATCH RFC v10 07/22] arm64: Initialize POR_EL1 register on cpu_resume() Message-ID: References: <20261109-kpkeys-v10-0-aa6c4d9603bc@arm.com> <20261109-kpkeys-v10-7-aa6c4d9603bc@arm.com> <7b92f7c8-1543-447e-8ef3-aba608141699@arm.com> <6808f3a6-1c12-4cb2-a109-30704d812490@sirena.org.uk> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6808f3a6-1c12-4cb2-a109-30704d812490@sirena.org.uk> X-Stat-Signature: rd4g76cceouj7gw74f6qo959kz7nu6tr X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6D68B40005 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1794489249-159964 X-HE-Meta: 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 AxEFlTX2 CsWTyAbr6mFMaSBTTLb2PEwYjsU7Z8Tq2I3OIqCLhzUc8a+hSJ6Hpms039GB5fgzs6+tiLGM5s2lFBBgy1Nz4vyt1iqsKBPItrb5ydez4+hA+6lgLV2A6yKdChUId5qkfJZStuCsoJEhMd6lUUVtus+aDDI+ObqItiXyrA4MNkvpJQPEyVzCanCHY854uursp2HgVvXqBGMNUQhx2daZH1N5kajtPUO8Z5Ue6nhA6Bh5uRTki08ZHOdiU9BETBOXNLMWSh+0jrx0Ew0OZc3h3da/nfsw8IKXhSm1Ql2UW2fhW4Hf/TNAFSXuK98xyErec0JyLD6LAMJBaZBtBHomQwgVkMDsHqyalBBmQH6X3szNiiazIykQarYtkjRsvaptyGp0Q7DwQPg2gz5U= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 12, 2026 at 01:02:16PM +0000, Mark Brown wrote: > On Thu, Nov 12, 2026 at 01:38:13PM +0100, Kevin Brodsky wrote: > > On 10/11/2026 17:36, Yeoreum Yun wrote: > > > > Thanks. seems required to isb() after initialising SYS_POR_EL1. > > > Agreed (as Sashiko reported as well). Presumably that means we also need > > an ISB after writing to POR_EL1 in cpu_enable_poe(), as that's basically > > the same situation. > > Possibly just have one before writing TCR2_EL1 rather than for each of > the indvididual features, that's harder to mess up? I'm not sure that's necessarily better, as we'd end up executing an isb() even when POE or other features aren't enabled. Wouldn't it be better to execute an isb() only when needed? -- Sincerely, Yeoreum Yun