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 16A6132A825 for ; Mon, 1 Sep 2025 15:13:32 +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=1756739614; cv=none; b=DVXmC+nkbqQTwVru9a1KaVLXYVvBHQP4jf0QmjopoxQBfdpSJx4fp117GYPQ1Fozg37DtgbqbcWjBHIL5NkdlNtzGQ7R95TNUtK0wyL3raEEvjJQxGV9HUPSvUYIAOlT1kLHmoHINTtD8GQ3YFusd5weiQA1cM+mt6zoYmtvqpw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756739614; c=relaxed/simple; bh=T/RAEzoBRkli0OidqH8/F4ZUiWPJufg9WZ3CV/HQrVs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FmF1F2Fu9XDZldIkKdrBlZh+ydYzdI3y5ABkm6uw6uvoius3Hdl9W7cVsByFyoGOKBDbI76XUjIRBjs/nW8jZl6SKZe1jP7JsvBuFDJhmydAyxI9rATylPuFLUa+dhrk93WKOuekMCN+eNNNuCPUMFgCI15VB8BV2QcWHo/X/1w= 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 26719175A; Mon, 1 Sep 2025 08:13:24 -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 847B83F6A8; Mon, 1 Sep 2025 08:13:28 -0700 (PDT) Date: Mon, 1 Sep 2025 16:13:25 +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, maz@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v4 4/5] arm64: initialise SCTLR2_EL1 at cpu_soft_restart() Message-ID: References: <20250821172408.2101870-1-yeoreum.yun@arm.com> <20250821172408.2101870-5-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: <20250821172408.2101870-5-yeoreum.yun@arm.com> Hi, On Thu, Aug 21, 2025 at 06:24:07PM +0100, Yeoreum Yun wrote: > Explicitly initialize the SCTLR2_ELx register before launching > a new kernel via kexec() to avoid leaving SCTLR2_ELx with an > arbitrary value when the new kernel runs. > > Signed-off-by: Yeoreum Yun > --- > arch/arm64/kernel/cpu-reset.S | 4 ++++ > arch/arm64/kvm/hyp/nvhe/hyp-init.S | 3 +++ > 2 files changed, 7 insertions(+) > > diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S > index c87445dde674..c8888891dc8d 100644 > --- a/arch/arm64/kernel/cpu-reset.S > +++ b/arch/arm64/kernel/cpu-reset.S > @@ -37,6 +37,10 @@ SYM_TYPED_FUNC_START(cpu_soft_restart) > * regime if HCR_EL2.E2H == 1 > */ > msr sctlr_el1, x12 > + > + mov_q x12, INIT_SCTLR2_EL1 > + set_sctlr2_elx 1, x12, x8 > + Nit: does it matter whether we reset SCTLR2 before SCTLR? I can't find a convincing architectural reason why they need to be reset in a particular order, but it looks a bit strange that the cpu_soft_restart and __kvm_handle_stub_hvc versions of this reset the registers in the opposite order... > isb > > cbz x0, 1f // el2_switch? > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S > index aada42522e7b..cc569656fe35 100644 > --- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S > @@ -255,6 +255,9 @@ SYM_CODE_START(__kvm_handle_stub_hvc) > mov x0, xzr > reset: > /* Reset kvm back to the hyp stub. */ > + mov_q x5, INIT_SCTLR2_EL2 > + set_sctlr2_elx 2, x5, x4 > + > mov_q x5, INIT_SCTLR_EL2_MMU_OFF > pre_disable_mmu_workaround > msr sctlr_el2, x5 Otherwise, I guess this is fine. Cheers ---Dave