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 BC5601531C5; Tue, 25 Mar 2025 12:34:22 +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=1742906062; cv=none; b=kodTnPyLttu+rzb8yDuT0bCKqkUTa8Zqzsjk2byhnija7owOvKPt46Nbuod1gtLyXX1/zTavqcGJA+7o9p1OBNuOXfW2F5MZkD7+G3QKqgXE+TF65ZwWS8r/0lc5Dnw1X3feU5vOuIl3YOxo+rRBVbgUgFNrsyJZK7UqXHgARQs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742906062; c=relaxed/simple; bh=2AB2CxwX+FpUSd8hg5qXA7pzt50UgH7rW3xan7CCKJo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IUc7Rqy1uUIHBufwPWkm1okileunnDvqm0k++9lHSNbn2nrGH0nO25PVL5W3fMJAX6Js4d1iI605JYdSoMsQNTFMVPqrgmbJU9+lklWBHYezue5PbsToSLuMlzYsN/xUFqJltbw4KyK7AuqIEkQyxVvZRP64hmj0VALCnymaMXo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ICRJmjHp; 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="ICRJmjHp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B678C4CEE4; Tue, 25 Mar 2025 12:34:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742906062; bh=2AB2CxwX+FpUSd8hg5qXA7pzt50UgH7rW3xan7CCKJo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ICRJmjHpQtfdto0WNPs5+A5uRbfSREoloyOA6SINMttIxSyoFoXhaDzmmJNN9LOK1 0AruUT3upgwKfb29VCIZDD54iC3qG+/3yYLTbH7QTfqgX0E+1ZmOKrKJtuRdQ/GQjP jtmnpIjaUBk7GaGRbfBuZOKIY1bPeu0GF1wPWYEI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mark Rutland , Mark Brown , Will Deacon , Catalin Marinas , Fuad Tabba , Marc Zyngier , Oliver Upton Subject: [PATCH 6.13 114/119] KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN Date: Tue, 25 Mar 2025 08:22:52 -0400 Message-ID: <20250325122151.969003212@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250325122149.058346343@linuxfoundation.org> References: <20250325122149.058346343@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.13-stable review patch. If anyone has any objections, please let me know. ------------------ 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 @@ -902,8 +902,6 @@ 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);