From patchwork Tue Mar 25 18:48:22 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 14029385 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E3B63C36008 for ; Tue, 25 Mar 2025 19:03:58 +0000 (UTC) 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:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=5fbZb8O063y2szKqurFj3dHdteN+I19L4oMjgjw4W/k=; b=SR0W71xRYv98vqILHWQQwgVVCU pfn8hhTiV3HxKJ++prMxbh2FtH/RGlBmYbyW0GE2toR1VAlvfa4sxH+pCZyrree58NAiz2vjp5+mI 4yBmbMjadzVM08V7BaF4n3bo12AveEIz1AEcBi1SLuKnf6c0THTwm2qihUKYfJAgzR0SeGh92ve8R YZpiAk27H3/yxT2ZTVt87pNBvfBdGdKQvY8tM3iAhJE4z86cuc0iVhrdIqF2XUsjqPsxS3WDEZ7v9 2iVe28Ff8AToUYPjaWopqtHxFigo7oOAyJ6Ol9bHj6i9P08XZCTbY4Rxe8swwLrbxdlhCV/7QKqyW 6gu6EdRQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1tx9Yv-00000006oEi-2zRU; Tue, 25 Mar 2025 19:03:45 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.1 #2 (Red Hat Linux)) id 1tx9LR-00000006lWI-2f0z for linux-arm-kernel@lists.infradead.org; Tue, 25 Mar 2025 18:49:49 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id C3EE2614C3; Tue, 25 Mar 2025 18:49:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F158C4CEE4; Tue, 25 Mar 2025 18:49:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742928588; bh=mkvTxdIaHOVoQg/PN+WHoGMe/wTgoxEDXWXJ93mvLPc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=eFvV423ZKHWcrxffpn6SAjkkkIylPE2tno5KDKeeGkgs3a6GeDzsWHCJwmsbE92m7 MfcXEk4nexNPtZT2T714NRwb6oIkEJoCJKIqjJp52x5D1uDzO2g3JrZpy3WYCSFjQ5 QtwyMCjhFHlMDvGm9aceUBJdTmDvGGpDwoaefbGKD4SuflJ7TFQjht3T+TXiQG3mxs c+aZeqwoY3A1cVKzhC67sTrn8nl5XRZQKVWcy1azCC/huaYDhm4ZR01WLg0aRM6ga0 9gKFKgRjYPfrqmXD3WzFUL3atgA3qGf4U//M/0n7MVnySt5paQHfL1bWYv+lOTo82S ZpUjqnYLwVuzg== From: Mark Brown Date: Tue, 25 Mar 2025 18:48:22 +0000 Subject: [PATCH 6.1 08/12] KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN MIME-Version: 1.0 Message-Id: <20250325-stable-sve-6-1-v1-8-83259d427d84@kernel.org> References: <20250325-stable-sve-6-1-v1-0-83259d427d84@kernel.org> In-Reply-To: <20250325-stable-sve-6-1-v1-0-83259d427d84@kernel.org> To: Catalin Marinas , Will Deacon , Marc Zyngier , James Morse , Suzuki K Poulose , Oliver Upton , Oleg Nesterov Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, Mark Brown , Mark Rutland , Fuad Tabba X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=5061; i=broonie@kernel.org; h=from:subject:message-id; bh=e8sm3bVdKGiSFMPfGMxoLS31b4Pe7foaJqQ4sSxvqLM=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn4vqscpJ+XGZeGryzI/YA13ZTYzfjGz3goro64dnl GtVJHs+JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ+L6rAAKCRAk1otyXVSH0FFzB/ 9rVAEmnovvGxTguFSumWqR9fYmivCJRYurw+/GlJIodM04qg/u9ZvW2xsLDngJIxlczEW22dmpJJpV ylZp+2pQaOjGwTkRSVbbB42Z76v5p3iNg2EqMMjbXi0Dvvp8YezHuAjCRuaz9R9a/HEKciCuIlRR7B S0Ge1e7H2iabInofA3MKQgeKFIktXh9nN0HyHJCVniZbzWfkxKpHLzF2vAsQ+Q9dqjlr7jhkOIOb5Y 97vVcM5o3tVIFzLO6rKP4zaqraxwdP1a+ugrGTxYQ/G8hOH49I2Cy03XK4da5HthHjZYMaU/FnBiGv oYhfCLuj+0OzDEpjXAbJT0J7L80wg8 X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Mark Rutland [ Upstream commit 407a99c4654e8ea65393f412c421a55cac539f5b ] When KVM is in VHE mode, the host kernel tries to save and restore the configuration of CPACR_EL1.SMEN (i.e. CPTR_EL2.SMEN when HCR_EL2.E2H=1) across kvm_arch_vcpu_load_fp() and kvm_arch_vcpu_put_fp(), since the configuration may be clobbered by hyp when running a vCPU. This logic has historically been broken, and is currently redundant. This logic was originally introduced in commit: 861262ab86270206 ("KVM: arm64: Handle SME host state when running guests") At the time, the VHE hyp code would reset CPTR_EL2.SMEN to 0b00 when returning to the host, trapping host access to SME state. Unfortunately, this was unsafe as the host could take a softirq before calling kvm_arch_vcpu_put_fp(), and if a softirq handler were to use kernel mode NEON the resulting attempt to save the live FPSIMD/SVE/SME state would result in a fatal trap. That issue was limited to VHE mode. For nVHE/hVHE modes, KVM always saved/restored the host kernel's CPACR_EL1 value, and configured CPTR_EL2.TSM to 0b0, ensuring that host usage of SME would not be trapped. The issue above was incidentally fixed by commit: 375110ab51dec5dc ("KVM: arm64: Fix resetting SME trap values on reset for (h)VHE") That commit changed the VHE hyp code to configure CPTR_EL2.SMEN to 0b01 when returning to the host, permitting host kernel usage of SME, avoiding the issue described above. At the time, this was not identified as a fix for commit 861262ab86270206. Now that the host eagerly saves and unbinds its own FPSIMD/SVE/SME state, there's no need to save/restore the state of the EL0 SME trap. The kernel can safely save/restore state without trapping, as described above, and will restore userspace state (including trap controls) before returning to userspace. Remove the redundant logic. Signed-off-by: Mark Rutland Reviewed-by: Mark Brown Tested-by: Mark Brown Acked-by: Will Deacon Cc: Catalin Marinas Cc: Fuad Tabba Cc: Marc Zyngier Cc: Oliver Upton Reviewed-by: Oliver Upton Link: https://lore.kernel.org/r/20250210195226.1215254-5-mark.rutland@arm.com Signed-off-by: Marc Zyngier [Update for rework of flags storage -- broonie] Signed-off-by: Mark Brown --- arch/arm64/include/asm/kvm_host.h | 2 -- arch/arm64/kvm/fpsimd.c | 31 ------------------------------- 2 files changed, 33 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 181e49120e0c4027aa52dd389de13f9ce5cd7b57..757f4dea1e563657eb5c79e624e4b91f514a113a 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -556,8 +556,6 @@ struct kvm_vcpu_arch { /* Save TRBE context if active */ #define DEBUG_STATE_SAVE_TRBE __vcpu_single_flag(iflags, BIT(6)) -/* SME enabled for EL0 */ -#define HOST_SME_ENABLED __vcpu_single_flag(sflags, BIT(1)) /* Physical CPU not in supported_cpus */ #define ON_UNSUPPORTED_CPU __vcpu_single_flag(sflags, BIT(2)) /* WFIT instruction trapped */ diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 8d073a37c266db3dc2726c6a0bb39c7e2586f53f..df050e4d3562d2ef36b7c27602a6feaa431dfa93 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -87,21 +87,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) */ fpsimd_save_and_flush_cpu_state(); vcpu->arch.fp_state = FP_STATE_FREE; - - /* - * We don't currently support SME guests but if we leave - * things in streaming mode then when the guest starts running - * FPSIMD or SVE code it may generate SME traps so as a - * special case if we are in streaming mode we force the host - * state to be saved now and exit streaming mode so that we - * don't have to handle any SME traps for valid guest - * operations. Do this for ZA as well for now for simplicity. - */ - if (system_supports_sme()) { - vcpu_clear_flag(vcpu, HOST_SME_ENABLED); - if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN) - vcpu_set_flag(vcpu, HOST_SME_ENABLED); - } } /* @@ -162,22 +147,6 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) local_irq_save(flags); - /* - * If we have VHE then the Hyp code will reset CPACR_EL1 to - * CPACR_EL1_DEFAULT and we need to reenable SME. - */ - if (has_vhe() && system_supports_sme()) { - /* Also restore EL0 state seen on entry */ - if (vcpu_get_flag(vcpu, HOST_SME_ENABLED)) - sysreg_clear_set(CPACR_EL1, 0, - CPACR_EL1_SMEN_EL0EN | - CPACR_EL1_SMEN_EL1EN); - else - sysreg_clear_set(CPACR_EL1, - CPACR_EL1_SMEN_EL0EN, - CPACR_EL1_SMEN_EL1EN); - } - if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) { if (vcpu_has_sve(vcpu)) { __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);