From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 24E932BE650 for ; Wed, 20 Aug 2025 15:11:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755702694; cv=none; b=po75AKuxKTTFqlgac5HPCSopnYZgzdvcHX9DTRjdTW9Hke0vbXCbjvLNh/HFNX/aOZ2e0czhXCyEZrUsWrQXXCMwJRVNCzH2TxppKUdnVK2qrrUrgImEXr/shNwU0u2ZtZECHyd4lUZIu70rBxJge38UzY66HCXU0E5RF4WaRbc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755702694; c=relaxed/simple; bh=VO9xsHFrbCLcnL58Q9qnzWr6MpdRTRLszsyRW06VVfA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XLoOq0bUqhS/CSv/HxW4WWwKEMXjmwXc+LJ4oqQ4q2ASwJqBUgMDHc4mpnlUpCv/G067/Of8rWwTCpGoCu/Pww6nBdH4MrOCxe23+CoDS+RsqZgUQfnDn181q1xUSLGaJgHxTq8zvOmNJ1GGhm3YjkkuKfWEZqLerhdzXvaGtqQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 63D991D31; Wed, 20 Aug 2025 08:11:24 -0700 (PDT) Received: from e133380.arm.com (e133380.arm.com [10.1.197.68]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C9CFA3F738; Wed, 20 Aug 2025 08:11:28 -0700 (PDT) Date: Wed, 20 Aug 2025 16:11:25 +0100 From: Dave Martin To: Yeoreum Yun Cc: catalin.marinas@arm.com, will@kernel.org, broonie@kernel.org, oliver.upton@linux.dev, anshuman.khandual@arm.com, robh@kernel.org, james.morse@arm.com, mark.rutland@arm.com, joey.gouly@arm.com, ahmed.genidi@arm.com, kevin.brodsky@arm.com, scott@os.amperecomputing.com, mbenes@suse.cz, james.clark@linaro.org, frederic@kernel.org, rafael@kernel.org, pavel@kernel.org, ryan.roberts@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v3 4/5] arm64: initialise SCTLR2_EL1 at cpu_soft_restart() Message-ID: References: <20250813120118.3953541-1-yeoreum.yun@arm.com> <20250813120118.3953541-5-yeoreum.yun@arm.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250813120118.3953541-5-yeoreum.yun@arm.com> Hi, On Wed, Aug 13, 2025 at 01:01:17PM +0100, Yeoreum Yun wrote: > SCTLR2_EL1 register is optional starting from ARMv8.8/ARMv9.3, > and becomes mandatory from ARMv8.9/ARMv9.4 > and serveral architectural feature are controled by bits in > these registers. > > Before, launching new kernel via kexec, initialise SCTLR2_EL1 explicitly. > > Signed-off-by: Yeoreum Yun > --- > arch/arm64/kernel/cpu-reset.S | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S > index c87445dde674..123564af345b 100644 > --- a/arch/arm64/kernel/cpu-reset.S > +++ b/arch/arm64/kernel/cpu-reset.S > @@ -37,6 +37,12 @@ SYM_TYPED_FUNC_START(cpu_soft_restart) > * regime if HCR_EL2.E2H == 1 > */ > msr sctlr_el1, x12 > + > +alternative_if ARM64_HAS_SCTLR2 > + mov_q x12, INIT_SCTLR2_EL1 > + msr_s SYS_SCTLR2_EL1, x12 > +alternative_else_nop_endif > + It would be better to do this based on the ID regs. Although the previous kernel _shouldn't_ have used SCTLR2 if the capability ARM64_HAS_SCTLR2 did not get enabled, it would be better to enforce a clean state here for the new kernel. If so, maybe one of the macros that you already defined can be used here? (But it's also fine to open-code it.) > isb > > cbz x0, 1f // el2_switch? [...] In the case where the el2_switch argument in non-zero, don't we also need to do something to reinitialise SCTLR2_EL2 after switching back to EL2, in the HVC_SOFT_RESTART handler? Maybe I missed something. Cheers ---Dave