From nobody Wed Dec 17 10:44:55 2025 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 68CCB13C914; Fri, 21 Mar 2025 00:18:30 +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=1742516311; cv=none; b=oqSqw5rYIM6UmfCEIhr2DAm5uK1R6ayhsFRWAatTTjT+R0ZKWEUq5VXEQY5z4pn0vMqjadjYgV0Ep4zQz8RG9tVPvLV+Cma0392WdSqrupOaiRgsF+AyyYQoi4OHSZH6AHXgShmNhRXR9zd+/0FJ0o9QCzuiF6XuMUEs0TzH07M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742516311; c=relaxed/simple; bh=ZqZu/OIKLFWaTlZe8i8EThKet2GXAnjLMbBwEC506ms=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ROukrnGJhEYUWnpeBZ0guux0NFGfEnJF5W1Yh3cgAOGAwowIvF7Af8HT8Xgv4aJ9F59sSXWG6PDZHMSokZOGu3WEjRZvolBwHpEI/wT10BbenJTpVTfyY1/CaOv3Dx4TOlH+KwSvPL8cmSPe/OpBC+WExQ+QfPz4Y/avrrbdAO8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BFJ/BWWt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BFJ/BWWt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 607DBC4CEEA; Fri, 21 Mar 2025 00:18:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742516310; bh=ZqZu/OIKLFWaTlZe8i8EThKet2GXAnjLMbBwEC506ms=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=BFJ/BWWtUsZOaVEr/IxKaarSBg4XbMl8SlTMKBYvTx2PBaCZfGKeG+gxJgpbN+rDU ZsJAUce7wJ1LLDfUlX6hBsaoUVuVGLKEGLoLLjsZecEIF+4TWCkHolEO9Fe6QtAV7c 7JarArWBWvJFPG3KXeBlkIaiUW8cefUiwodowrf7jOzYd25zNXbE2OH2bXa7G/Q1gh gdsmYsjuT8FJ5RB5A2TDm3AC8Fd4Pmie5+72ZKVwmoaMQXHJ/wxpfnX7bfZgRO6Pb4 ke20UF0F2v0BqHq/iBXU7WbeVTvP2I3TJgFmRqpe35xxk23wRiBsadCjtHltkvI/cy ca6YYGLXckBXQ== From: Mark Brown Date: Fri, 21 Mar 2025 00:16:05 +0000 Subject: [PATCH 6.6 5/8] KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250321-stable-sve-6-6-v1-5-0b3a6a14ea53@kernel.org> References: <20250321-stable-sve-6-6-v1-0-0b3a6a14ea53@kernel.org> In-Reply-To: <20250321-stable-sve-6-6-v1-0-0b3a6a14ea53@kernel.org> To: Greg Kroah-Hartman , Marc Zyngier , Oliver Upton , James Morse , 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 X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=4610; i=broonie@kernel.org; h=from:subject:message-id; bh=KPoLYPWBSzZcnvIISNKfbhEVULIfJGkJjRCo5GPoRtE=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn3LA9pLOeOCWXk9Bbg48Gc9v306SXIZRAlw1DjtCr WLkRbLyJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ9ywPQAKCRAk1otyXVSH0KgXB/ 9ZLaJiuCyWeNYOKY8BZOaoZ6dmEqQ0N45Y5Xzgtr/vTR8M44uNGSe2zyltCQQBuwo5psuyWo76ouL6 1kW7Onpbr+xcgreb0/VaNkPKnDorCSYBYpQQ/8om2dXaWJUkirAqiyLO97exbHaEvtxjOtkf+OyxWA 26Nf2+zg/RDq+v46eh2SjmaE+0rV1DQjugqFW0FoPR5jzM1GpVT2QVUzPQYoCH1GLRgIsP519oRMck 2t96jxJwPB43jw18VD23fGh/Svvav5xmTVcZocGRwdxINY4v9rsxsF0hw0dCF1QYmIaZYTR8C2n9OA D8k23BSRQx7ezSkYx8z5aafCr/LAKy X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB 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=3D1) 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.c= om 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 | 23 ----------------------- 2 files changed, 25 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm= _host.h index 9c1056d6f6859522dcee4b8c4e4804a7abac93d5..27c53b603d693d1cfe8d81f94a5= 9d3afb665be8e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -717,8 +717,6 @@ struct kvm_vcpu_arch { /* vcpu running in HYP context */ #define VCPU_HYP_CONTEXT __vcpu_single_flag(iflags, BIT(7)) =20 -/* 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 f1fe7abbcb83393e7c3402405bb7b1fdbf6024ff..0492a1fc718130934f8bada836f= e42bea6db7abb 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -87,12 +87,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) */ fpsimd_save_and_flush_cpu_state(); vcpu->arch.fp_state =3D 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); - } } =20 /* @@ -157,23 +151,6 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) =20 local_irq_save(flags); =20 - /* - * 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_EL1_SMEN_EL0EN | - CPACR_EL1_SMEN_EL1EN); - else - sysreg_clear_set(CPACR_EL1, - CPACR_EL1_SMEN_EL0EN, - CPACR_EL1_SMEN_EL1EN); - isb(); - } - if (vcpu->arch.fp_state =3D=3D FP_STATE_GUEST_OWNED) { if (vcpu_has_sve(vcpu)) { __vcpu_sys_reg(vcpu, ZCR_EL1) =3D read_sysreg_el1(SYS_ZCR); --=20 2.39.5