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Tue, 10 Nov 2026 08:36:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1794328579; bh=W93zuHvv0B3GjuQYbnfR2B0hYUYTD/1HhAutAvOyHc8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sYozmqnTmmj1HDyt+LmelivUTXfURzy4ZuotqpQSAnyER6/dyDFtKIFkVkn0SmpO+ O+RU5XZyaIzhycu65Pmw23utreNYCUqv9PnuZP1DrGLbr5D7k6uP7oHKi7dXqKJdYN CbmlR/v3UEIQ3c8AHIpFUW0pKrLveLcUhkh7pNdA= Date: Tue, 10 Nov 2026 16:36:12 +0000 From: Yeoreum Yun To: Mark Brown Cc: Kevin Brodsky , 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 , Yeoreum Yun , 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> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261110_083623_076936_83239B51 X-CRM114-Status: GOOD ( 13.10 ) X-Spam-Score: -4.4 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-5.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Nov 10, 2026 at 03:53:30PM +0000, Mark Brown wrote: > On Mon, Nov 09, 2026 at 03:58:32PM +0000, Kevin Brodsky wrote: > > From: Yeoreum Yun > > > > The POR_EL1 register is reset to an unknown value after cpu_suspend(). > > Since POR_EL1 always holds POR_EL1_INIT when entering cpu_suspend(), > > initialize POR_EL1 with POR_EL1_INIT before cpu_do_resume(). > > > +#ifdef CONFIG_ARM64_POE > > +alternative_if_not ARM64_HAS_S1POE > > + b .Lskip_por_set > > +alternative_else_nop_endif > > + mov_q x2, POR_EL1_INIT > > + msr_s SYS_POR_EL1, x2 > > + /* isb can be skipped since cpu_do_resume() will do it. */ > > +.Lskip_por_set: > > +#endif /* CONFIG_ARM64_POE */ > > cpu_do_resume() will update TCR2_EL1 to enable POE again, a sufficiently > unhelpful implementation could potentially decide to do that before this > POR_EL1 value takes effect AFAICT given that there's no barriers. Thanks. seems required to isb() after initialising SYS_POR_EL1. -- Sincerely, Yeoreum Yun