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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-Stat-Signature: ck4i14u54h7yc8bq7jw4s37dpqp5ouan X-Rspamd-Server: rspam01 X-Rspam-User: 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-Rspamd-Queue-Id: 6C5BF180004 X-HE-Tag: 1794328580-440432 X-HE-Meta: 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 8hSi9Lnf Pcv+J+bhwRo870NlFYspC1jjvPwozz7R8Yq8XXwE03R+xEcbM5mouSMd+p8CSNTQD7ez1Ygnb1lcyj5bLZ3TznE5g63suFf9ND817NCxEmYLPJHQFz1xvZmT7GxoGVTRrZrFyWfptjs97O84Uivj8Fd3wx5nrnqpQvZJ1z6mhy1f7Hcx+gNT8rPp/GQZqMcnMpz7RK1b0i0AviZ10g5FCiTJBhxvDhB/twBTXthSbZjxYo5fLncjhvJAGwi6dEIUmOyBSCDojTJ+oug8a3SBIgsZeGOsRlun35M+sE3FyR/mPJbgB6u49mt8QyghmBi5M9dvS/M9pNj0wpLVRXgcknXlcXj2BuGQvVXVqi5d1CRDcVqugy6Trpa4qEmg6AO8I124GVDyotMgn8kz5pOdrUL0cdGN65UhCexW8yw4hE/KG+xqC6akgi2KGEiQVD4CXj47M 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 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