From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6ABC6288DA; Mon, 24 Mar 2025 19:00:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742842843; cv=none; b=O+h8HF5vAqFKL3DXzJ7kMBq3AooYnvuvrI/zG6/59T9c5GKxzghVqUnoMDl22RE/Ys9QxWQdETs4AafaHRPozPrVdc37X2O8fwgPOBueQo6iGA9UKFh2oEsfPYuMovVQA9kj9nE7svXNfs9o3mV/B8RytSFVSgqaCmPcCcAGiWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742842843; c=relaxed/simple; bh=agw0W7rWLyfMIOL6qFurg01tHeni6ud0VRvBPFPaUbo=; h=Subject:To:Cc:From:Date:In-Reply-To:Message-ID:MIME-Version: Content-Type; b=kCBtJUSkNa/6qytBJ5KSUdHfy5OM5gKXm9yGrmByJ+X7/ALcj+7PZOQWDoCWUKV656qfwtEm5XlRrh7gzcomg0navw9Xwy+phsNXh0Es9+woD3aJ0Bso8ep0KXSxeW8lJMpIT7iQZnQrggSxC+ALVu+ysKeE0nBC9X25u9Q42V4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TLnmj6jT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="TLnmj6jT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A526AC4CEDD; Mon, 24 Mar 2025 19:00:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742842840; bh=agw0W7rWLyfMIOL6qFurg01tHeni6ud0VRvBPFPaUbo=; h=Subject:To:Cc:From:Date:In-Reply-To:From; b=TLnmj6jTAPfELJyd11bRrJkT2pNvOGBeQz4kvgH+OyqSaISPxEA9Y0eZnMT3f4UsZ lnxaVTooFiXS8tZ68Kys5JJxXt5T51jcl/N6GkEnlWwaIhDOLxP7QDQ7gq89JdzAKS N/C7xcPkfoFEJ0AgfJ1L2aWUTiwA27A+4LO0oubA= Subject: Patch "KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN" has been added to the 6.12-stable tree To: broonie@kernel.org,catalin.marinas@arm.com,gregkh@linuxfoundation.org,joey.gouly@arm.com,kvmarm@lists.linux.dev,linux-arm-kernel@lists.infradead.org,mark.rutland@arm.com,maz@kernel.org,oliver.upton@linux.dev,suzuki.poulose@arm.com,tabba@google.com,will@kernel.org Cc: From: Date: Mon, 24 Mar 2025 11:59:05 -0700 In-Reply-To: <20250321-stable-sve-6-12-v2-5-417ca2278d18@kernel.org> Message-ID: <2025032405-rumble-backroom-ccb8@gregkh> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit X-stable: commit X-Patchwork-Hint: ignore This is a note to let you know that I've just added the patch titled KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN to the 6.12-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.smen.patch and it can be found in the queue-6.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >From stable+bounces-125711-greg=kroah.com@vger.kernel.org Thu Mar 20 17:15:08 2025 From: Mark Brown Date: Fri, 21 Mar 2025 00:13:01 +0000 Subject: KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN To: Greg Kroah-Hartman , Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Catalin Marinas , Will Deacon Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Mark Brown , Mark Rutland , Fuad Tabba Message-ID: <20250321-stable-sve-6-12-v2-5-417ca2278d18@kernel.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 Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/kvm_host.h | 2 -- arch/arm64/kvm/fpsimd.c | 21 --------------------- 2 files changed, 23 deletions(-) --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -891,8 +891,6 @@ 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 */ --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -65,12 +65,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vc fpsimd_save_and_flush_cpu_state(); *host_data_ptr(fp_owner) = FP_STATE_FREE; - 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); - } - /* * If normal guests gain SME support, maintain this behavior for pKVM * guests, which don't support SME. @@ -141,21 +135,6 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcp local_irq_save(flags); - /* - * If we have VHE then the Hyp code will reset CPACR_EL1 to - * the default value 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_ELx_SMEN); - else - sysreg_clear_set(CPACR_EL1, - CPACR_EL1_SMEN_EL0EN, - CPACR_EL1_SMEN_EL1EN); - isb(); - } - if (guest_owns_fp_regs()) { if (vcpu_has_sve(vcpu)) { u64 zcr = read_sysreg_el1(SYS_ZCR); Patches currently in stable-queue which might be from broonie@kernel.org are queue-6.12/kvm-arm64-calculate-cptr_el2-traps-on-activating-traps.patch queue-6.12/regulator-check-that-dummy-regulator-has-been-probed-before-using-it.patch queue-6.12/kvm-arm64-eagerly-switch-zcr_el-1-2.patch queue-6.12/kvm-arm64-mark-some-header-functions-as-inline.patch queue-6.12/kvm-arm64-remove-host-fpsimd-saving-for-non-protected-kvm.patch queue-6.12/regulator-dummy-force-synchronous-probing.patch queue-6.12/kvm-arm64-refactor-exit-handlers.patch queue-6.12/kvm-arm64-unconditionally-save-flush-host-fpsimd-sve-sme-state.patch queue-6.12/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.smen.patch queue-6.12/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.zen.patch