From patchwork Fri Apr 4 13:23:41 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 14038494 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 EED0DC36010 for ; Fri, 4 Apr 2025 13:43:28 +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=TK8MWaq0g9D90faJmCGZsneM13Zdzn3fIPEF+xECAnA=; b=lckzYR2AW2YT0bY1UAt5cHZLvU cEpfrM2gGI/018oFiO4ERHNKdvwLeOT4CvxEtuTj0vkoFjwFnssgQnfu2BujiSqtH7sHRbeUnmJbx 7K1d2o2pi3mgwuAchMX895/N35/EA7BCfeh4+Qcd+uhhl/QN0qYeRDP1X8zSwuYAD2Ivqc+S9KBI3 Fi8EOaZs0pUFMOxSACUxD5FN4RdIfRymEgcfHrhcj1U59Pp5HRFAI0wZaFgpCKRXGSvI32Amqmu1A H4dhEYp+g03x5cDUYJmlb4svJrH8uJfQTYLT0g5992Y9XDObLqpRbHo04Dydk66Upt0aAwotTlTYg t3Ay6f0g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1u0hKK-0000000BsIs-4Ahz; Fri, 04 Apr 2025 13:43:20 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98.1 #2 (Red Hat Linux)) id 1u0h5P-0000000BpCJ-42xW for linux-arm-kernel@lists.infradead.org; Fri, 04 Apr 2025 13:27:57 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 4703EA47391; Fri, 4 Apr 2025 13:22:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE541C4CEE8; Fri, 4 Apr 2025 13:27:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743773274; bh=5jtExQAwF36VmhyMCHSi9Dr/NqZucqSesDzOeduLG/o=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=ppBbXraMvMtezZw0mtRX/D3prPXYwFn4idOQRkPUNn/P6Wi+wvrhrs3BF4WAbmePH qMnGZskheFh5qRr6VhJ+1wfsaU/tgTB2Bb7mKSVvYmmhUjUWHbqHG/7apo/C6qgwOZ 6rg8SM/jM9Btr/up8vSVtbGFeFxM4I9EF3FD1hhbHS/YcXHnVSsc2dhJShMTVfMwaW /Vc0Gj0gamVP7zupprmM/YD9w5x/97V/8RNEv7nMHXoJji/ZTjb3y5RMBBUmF9CVz9 1nCgay16U3yd7HZwYzMLMM1wtAuOTcpMFtb91lE41X91TBe3iexRDMyyTdFARuSE49 8tWSQyKNJAELA== From: Mark Brown Date: Fri, 04 Apr 2025 14:23:41 +0100 Subject: [PATCH RESEND 6.1 08/12] KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN MIME-Version: 1.0 Message-Id: <20250404-stable-sve-6-1-v1-8-cd5c9eb52d49@kernel.org> References: <20250404-stable-sve-6-1-v1-0-cd5c9eb52d49@kernel.org> In-Reply-To: <20250404-stable-sve-6-1-v1-0-cd5c9eb52d49@kernel.org> To: Catalin Marinas , Will Deacon , Marc Zyngier , James Morse , Suzuki K Poulose , Oliver Upton , Oleg Nesterov , Greg Kroah-Hartman Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, Mark Brown , stable@vger.kernel.org, Mark Rutland , Fuad Tabba X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=4949; i=broonie@kernel.org; h=from:subject:message-id; bh=gGHtRWYkZIvY26SXOdVNVzxHFFds99XjbSYEpsfkvMA=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn794zFUdaBACXWoPRSc+Uzt5n9EGMEGdRPsJxZucS WnPxH7qJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ+/eMwAKCRAk1otyXVSH0IDXB/ sFJjCz99+FG6SozKUpw53LUEDTn6jY5vGIUuIzPGQF9N5skIQWMdeuAtILn1tlUKxgCW2rkZh/hC4l Tr2X25rfWH4MvZFriO1xrRWQ6GMObYthRFvxPEsYHLd8x2MP5wdo+gAqthHQX7l713p6vypYpjBfyV quZztHHXhG66hfCPbmFLk8kJSarEQn0XhyHC0ubUSHrWEYZZXnpGMm4SGONKuc8RW76ebtIp02GQDG TjRu4hImQbXDmW0DhfKDdcyEurPDdrfSQeQ7FC3wqTubnz4SQlKoSg3Hu8kijf7hWolyxQ1BxlWcz7 BJVSpV1qs/bopL8wxZjc9OQXNHEQYn X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250404_062756_139608_00895CAE X-CRM114-Status: GOOD ( 21.58 ) 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 | 31 ------------------------------- 2 files changed, 33 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 181e49120e0c..757f4dea1e56 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -556,8 +556,6 @@ 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 8d073a37c266..df050e4d3562 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -87,21 +87,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) */ fpsimd_save_and_flush_cpu_state(); vcpu->arch.fp_state = FP_STATE_FREE; - - /* - * We don't currently support SME guests but if we leave - * things in streaming mode then when the guest starts running - * FPSIMD or SVE code it may generate SME traps so as a - * special case if we are in streaming mode we force the host - * state to be saved now and exit streaming mode so that we - * don't have to handle any SME traps for valid guest - * operations. Do this for ZA as well for now for simplicity. - */ - 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); - } } /* @@ -162,22 +147,6 @@ 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 - * CPACR_EL1_DEFAULT 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); - } - if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) { if (vcpu_has_sve(vcpu)) { __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);