From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BFEA5606A323 for ; Thu, 12 Nov 2026 12:38:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=PJrQYXPj; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=G92ewwS6 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=qwGHYWqkzjPKzDNH4i/tvvgZ4hxVWyzdRGgiuO5uYi0=; b=PJrQYXPjDekyfT WQNZZMQukA2CuF4ez/zv+s4FxBuNVAssIOQtKk/JsHeXGvxwmZUz2ndtJzvw57oIKL+2bNlBDImVR s68Paz/brHD+9QKZHXtZrwfQBO9ZqmuM7ELfCbbwjQJnWHW7sWdCNIkBHQ762BcBVe7WEJMwYnmMv MQj3V6Cd2ONZVO8V2u7IwkKwOjJvcSRYF+CyiMBMyAEpvUFMocXCrMtDyHt6ycfc+OhEjbXYCr+mC g6NY+8YcCdOzeytRAk/pGSAiP5KJ5EV7jo9CWLJHbPzMS5KgXmWOYq73vzR5/WAtCH8NvxrFTKjBp N41VKCAnSRBLD8YW6/uA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xRU4R-00000009u2J-32xj; Thu, 12 Nov 2026 12:38:27 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xRU4P-00000009u1k-2Shr for linux-arm-kernel@lists.infradead.org; Thu, 12 Nov 2026 12:38:26 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 354211477; Thu, 12 Nov 2026 04:38:21 -0800 (PST) Received: from [10.57.59.183] (unknown [10.57.59.183]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F0E6E3F673; Thu, 12 Nov 2026 04:38:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1794487104; bh=GXDArifiTXzGS/TEyKUeQy694OV8tzZyyHhxUDTufKU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=G92ewwS69xI/sQnwPuFxDuaGeeicD5gWXRAQcqnYkeOnE+1AhuhQD+T9u+2gEnSvA 8Tz0b5fy8Nanp500jVMIfPIBqybgWOu28wUx9eUNS6BsJB8hlKLfKfowurrVqb8yg0 gegWtANRaNOjC5bAe0P7rnTdXxQKCb9wTnu50CiQ= Message-ID: <7b92f7c8-1543-447e-8ef3-aba608141699@arm.com> Date: Thu, 12 Nov 2026 13:38:13 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v10 07/22] arm64: Initialize POR_EL1 register on cpu_resume() To: Yeoreum Yun , Mark Brown 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 , =?UTF-8?Q?Pierre-Cl=C3=A9ment_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 References: <20261109-kpkeys-v10-0-aa6c4d9603bc@arm.com> <20261109-kpkeys-v10-7-aa6c4d9603bc@arm.com> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261112_043825_667928_FC6FFA85 X-CRM114-Status: UNSURE ( 9.15 ) X-CRM114-Notice: Please train this message. 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=-7.4 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,USER_AGENT_SANE_1 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 10/11/2026 17:36, Yeoreum Yun wrote: > 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. 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. - Kevin