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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=kSgH+nQG; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A3DD360A260A; Tue, 10 Nov 2026 15:53:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=kSgH+nQG Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B92A1F008A3; Tue, 10 Nov 2026 15:53:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794326020; bh=4qaBcoJhuip85HNRKTiRsc6cXmbUnKal0wM/bMhZ1/4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=kSgH+nQGYPhpecDT9RjX6A/Px+LoAnOuAhiSotnuroSbtWAmzKYW4psaCtAgm3HTu Ud6V+EHkVE3/ElaMQwFldGXubSt6xnnZ/H3lgzIXO1EM8FVi1btcbv6Q58NdTqn5kX VSwm6LEMTkaplsK5V9TVhOGb77Pc7h/AvO0sKyFHmtojeCKTH7meWA2i2lB3xJQORv LLCXQjH6SckaZOufXYpZi4+dMGxI7LRSKGENk099kRFe/hVqBoPU2XdsQ5DcgYensD /N1jMWwlSmjxHjQj70tuBOg1mUKeFDv3uHaSqSd+3wj7rolN0iCh/5JK3PXXFiZxS4 +LKdNCB+uEhVw== Date: Tue, 10 Nov 2026 15:53:30 +0000 From: Mark Brown To: Kevin Brodsky Cc: 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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="y6i2pjiKjCxCKcN0" Content-Disposition: inline In-Reply-To: <20261109-kpkeys-v10-7-aa6c4d9603bc@arm.com> X-Cookie: You can't take damsel here now. --y6i2pjiKjCxCKcN0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Nov 09, 2026 at 03:58:32PM +0000, Kevin Brodsky wrote: > From: Yeoreum Yun >=20 > 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. --y6i2pjiKjCxCKcN0 Content-Type: application/pgp-signature; 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