From patchwork Fri Mar 21 00:10:14 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 14024713 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 BD1E2C28B30 for ; Fri, 21 Mar 2025 00:19:35 +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=XbS5WHn14arEHctM5lngaRY3uhDw8toPfz7q43QpcCY=; b=vkL5h2rYCPFVqM4npGJ7C0CAj3 MBU6MZ2rHRoXuzRcqHVnOUmk0hlGwCL0AhW7C6ReJwpQlAyP4xVzJicC4VJoYnfyb/AduVtr0zb7o mEvpDxlcHvdLy1gpsi2Ljj/1jAzLsDQjphoqHg2k2uBAcZqsL2efroBG53ay1nP7K4yfOEE99S8tg 97QZkvz+BQIEQle99M5iJaojfmPvvvQl3+PGGSaZQCsuA4f7GI67M5ZI9PlmSeRGumSFsgkDRwOKZ lo947W9Vnfni5BoS541tEU6LaAec2tj9JS9eGDuubTeOltMlulHaLN5kfyuTAeKJCT8gIJRL1Qk5Z +i99o1rA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tvQ6c-0000000DXbj-3Sh3; Fri, 21 Mar 2025 00:19:22 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tvPyU-0000000DWJE-2cf5 for linux-arm-kernel@lists.infradead.org; Fri, 21 Mar 2025 00:10:58 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 1DD856159E; Fri, 21 Mar 2025 00:10:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C71B7C4CEE3; Fri, 21 Mar 2025 00:10:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742515857; bh=bw43+XI1pckdNtniIOtil4SJwIekSgoH7HvyZXHg1qA=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Wob2BTQkjk8R9W8rECTaBsKdvGyJjN4nK04fI4ADtYnwa9XR+3DrbjeobSoXeW1Ra CgOwCYp3gSMSWCLnxbMZH6nCPwj3d2U1LZF8IMNHQuowpunRIhsTwRWRyQK7xcMaNj c3xR3JYmIom+gtdNhP0i4cGRIZN2i6NbKpk6vghcOX23QTvfs8o8EKOSLIMW4cLKwy rwDGKZB5cbiilfmFGvjG8CcnxC6R18kM2SWQGKHYjpBoLgqFt2tQJtIWozi2k008Cq f6coRyLgdfI0cgPEWqxEDjh5Ag7+cOA2Sj/IRrAYs909PTDZA7y4uB1f1AnaewNL0g +zAZDKua5Ci1Q== From: Mark Brown Date: Fri, 21 Mar 2025 00:10:14 +0000 Subject: [PATCH 6.13 v2 5/8] KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN MIME-Version: 1.0 Message-Id: <20250321-stable-sve-6-13-v2-5-3150e3370c40@kernel.org> References: <20250321-stable-sve-6-13-v2-0-3150e3370c40@kernel.org> In-Reply-To: <20250321-stable-sve-6-13-v2-0-3150e3370c40@kernel.org> 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 X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=4631; i=broonie@kernel.org; h=from:subject:message-id; bh=KPO0pMf/f4hzNo7O+4ORc0iTjEcZ2saBRPtDAXpQPO0=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn3K53NCIK+0T7a4DKTLLE6v2Zr7zVILM3BfHegMg0 I94VU4OJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ9yudwAKCRAk1otyXVSH0DN7B/ 9Cap64hoWGEJL5wQP32lxgKtJDP/KaNywIK/Ync5h5ozwPtfpnS+dZzasAxRCZbGTOJ3w2Hc7c1qbk XJn6MtPgDcun0m5NGKk+kkBZkppxswoNY+loI6A3qKx/25hBGa0NasXteSbjihPYZ/zVWF/A+s1qNH 9eqEemritFtDfEQf8YL9FqxTHC8hag9urGaUVLDb5sRQjTNpyYaqlX6pWoQU4LqgPWYhuPhYq3aDjB 2K/6P9t2EGNjsg9kTw0hFn9T/DVC/ect6towvxX+9B+bbdWrAgXtSkfx3wLYPxu/1tahTea/f+PdVT luZMLU6avvPrVmRGxnTGOYsFYGwf5Z 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 | 21 --------------------- 2 files changed, 23 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index fe25d411d3d8efbe19d5ffba8ea23bf98eb06c38..06e3cfc9a73b8c95712580b13b926b6471a16be7 100644 --- 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 */ diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 4127abfd319c2c683d2281efa52a6abe5fac67ee..f64724197958e0d8a4ec17deb1f9826ce3625eb7 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -65,12 +65,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) 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_vcpu *vcpu) 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);