From nobody Thu Dec 18 07:11:52 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 345765103F; Fri, 14 Mar 2025 00:35:48 +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=1741912549; cv=none; b=WfDI3qpufDxyadUsH+OmtllX/ynqcMjTH2LA4kMsOtyc1qK7CCbZAmmFRtjtXg2yhnFtUwHn9XWPYUY7f7F9HYgDBxG6qu2EAoCkOOqCKOPLN3Mcw4okhsqvLuAVm/z7sDjVe5PSYf9Nskxghg5oGjg2MFtBquO2ohlZ/s7vCW0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741912549; c=relaxed/simple; bh=HIGP6VBVWear5iflnuFs+CJgbgmTu67qH3gNvcXNftM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=FwKlq1k+YUrAjF2UawUD36MqL4Ui0OFhhqutShz6jIXOxXk6Vo5w0kPvyLAgef2hnXutCrtp9X/fuGf7pUPNnKiZeAPKsk9Hn/U+4a+6oOr0gOCiUnMZgFgsdm4v0/X+zxgKFKM7tF3DplUvfqX7yl/dvvN8AQfhKZtHCd/gVo0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AGjYGP2Y; 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="AGjYGP2Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 073F9C4CEEA; Fri, 14 Mar 2025 00:35:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741912548; bh=HIGP6VBVWear5iflnuFs+CJgbgmTu67qH3gNvcXNftM=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=AGjYGP2YJS1aamsClgwJVp8lf/kvGD7uAoY25yBI1REbemyE74WLcQq+g06M468KS aUnhTHifE1olwyulIXOfBegwsLtZU3L+PD+pKyAwyf2vmFxif5nqvz5i3pCeUR9361 vA3QrC0POnnxP8GMCB7ZibojebO9BYXEeD6zPS8ONfPixf1JLhC0OrmDBggVSzbJJf YxUU9Zw2ARStBU/VEzBgs/NxsItnxNFSSQAViGOr/Bd+73QS9eNS51zzODz8yS35Bn WOz/59OHaZRjIR4iZcrtLw2URol/L2smOLmeCBst5gk5bgvV4GVQLtddWLcqnQFPYP MsZ2DhXlTQKRw== From: Mark Brown Date: Fri, 14 Mar 2025 00:35:17 +0000 Subject: [PATCH 6.12 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: <20250314-stable-sve-6-12-v1-5-ddc16609d9ba@kernel.org> References: <20250314-stable-sve-6-12-v1-0-ddc16609d9ba@kernel.org> In-Reply-To: <20250314-stable-sve-6-12-v1-0-ddc16609d9ba@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=m4KZU2ZKwzrjocVTNsB04VCPKKuL2LaKvOlEuHx81YI=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn03nMSFXYqxcla2yOd8Q6on5+uQX/712+j4Vs6YuY SKd3+2qJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ9N5zAAKCRAk1otyXVSH0NwpB/ 9R+P4tBBfHyjajsFRWu7iejmODR6/43awUkFAy7YdjeXS6OC7DNo1d0jkkT+kNF+Ep0vF1ThBl1aXm kWW2QxCv7ixy2vRkXOFjUkoZBzyK28avR1VQ0o2+CL5E/PV4dqncMKypK7Bc22NYh5c4npcXhLgiS+ FZjjcjQoGIq+I9r+dSQPA0LLOtCtB/Wqq9uUY5RT76bydSYgs5aRDsTU7uK0QXBcRQsW8QbDTRBJjU PdSw4sVNx6DU0sOGN7/xtoN9vOT7S8TUZS1zDI6+sOy+qEGCBBJ5XgI9cLevDs1ltX5awZO05gRQhu 2KA92X3cjMs8+lCWAguTV7tORpNOCx 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 | 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 1a126fa657fcde3433f37f3aaf464a5b6a5f095d..122a1e12582c0584bce86c5416e= f7d150f90fe95 100644 --- 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)) =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 4127abfd319c2c683d2281efa52a6abe5fac67ee..f64724197958e0d8a4ec17deb1f= 9826ce3625eb7 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) =3D FP_STATE_FREE; =20 - 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) =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_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 =3D read_sysreg_el1(SYS_ZCR); --=20 2.39.5