From mboxrd@z Thu Jan 1 00:00:00 1970 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 69E2EC48260 for ; Mon, 19 Feb 2024 09:21:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=potdHoUVcZ5VbmiZT+PkgCUT8H6mGYhGQXqeDE7prVQ=; b=0MGNO9bl1M+Jac yyUVecegUN5x4FusCtY/HogpYiQMcLUIDnu5WbMO4eamJYAKjrXKx3g4ECKJHmSw3QD03As5Hjz73 T6KXPK/72yGAoOd72YkVuQ/YDhocwlE3HhmtMo3Q6FQh1w8sF3Z05ZI6QXfSAeHLJ+H05Gg4alHWv mWCWKIl3xvI6mKr2L6Ks4ryCfD1dd8wBCeREJfTwAjtGCavz+zkZYWLl+KQtE/ZUVhPyVeRh2uryO lzQjXbsESDgZU5TzgGVbHd22uklUtrtn1yaBdQUtw9dIAxvASPNU74NxeCUzdeNLUjuEDEvbq3Clm DHcdgZlFzdc7ZM5hfvUg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rbzpj-00000009mNh-1dbV; Mon, 19 Feb 2024 09:21:07 +0000 Received: from sin.source.kernel.org ([2604:1380:40e1:4800::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rbzp5-00000009lxY-1CNu for linux-arm-kernel@lists.infradead.org; Mon, 19 Feb 2024 09:20:29 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 47310CE10B2; Mon, 19 Feb 2024 09:20:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 671B1C43141; Mon, 19 Feb 2024 09:20:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1708334424; bh=gHuw6gM0kxaTDkdludLUngX+0zZfHKbDwECjHkZh6xs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=A8ok9AVuLASRtCeECwevq3T7az8dloz4F58X2n4txtC+nzXPNCaGOB4+W9SQoRTj3 HqosrySHNBYwnlJA7ze6Vplik6S3GYFhpiw4qS1+X8FgP4kPpL7PG1rW5fOqTc6ca9 1VaFpzjWtPF4TcNeatQORbYYf0gBMSnNgr5dHK7dEmbycxSe3p14Mpj1VZJJKjN3I/ fCpWkiTCPkoBchr4+I/ge1+BGIscR9d60OrfPz/3+QitUML7CjnqNEA/3ZlEXz95d3 gXuPiT16HRLhrCNWW/TM7Peg4aMw6zdcaDYGN2jhU2aR3DXroKydy+RDhyyEbS/2ml hLqnQgg10uyCw== Received: from sofa.misterjones.org ([185.219.108.64] helo=valley-girl.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1rbzp0-004WBZ-J5; Mon, 19 Feb 2024 09:20:22 +0000 From: Marc Zyngier To: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: James Morse , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Will Deacon , Catalin Marinas Subject: [PATCH 06/13] KVM: arm64: nv: Fast-track 'InHost' exception returns Date: Mon, 19 Feb 2024 09:20:07 +0000 Message-Id: <20240219092014.783809-7-maz@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240219092014.783809-1-maz@kernel.org> References: <20240219092014.783809-1-maz@kernel.org> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, james.morse@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, yuzenghui@huawei.com, will@kernel.org, catalin.marinas@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240219_012027_879788_1B18F666 X-CRM114-Status: GOOD ( 19.64 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org A significant part of the FEAT_NV extension is to trap ERET instructions so that the hypervisor gets a chance to switch from a vEL2 L1 guest to an EL1 L2 guest. But this also has the unfortunate consequence of trapping ERET in unsuspecting circumstances, such as staying at vEL2 (interrupt handling while being in the guest hypervisor), or returning to host userspace in the case of a VHE guest. Although we already make some effort to handle these ERET quicker by not doing the put/load dance, it is still way too far down the line for it to be efficient enough. For these cases, it would ideal to ERET directly, no question asked. Of course, we can't do that. But the next best thing is to do it as early as possible, in fixup_guest_exit(), much as we would handle FPSIMD exceptions. Signed-off-by: Marc Zyngier --- arch/arm64/kvm/emulate-nested.c | 29 +++------------------- arch/arm64/kvm/hyp/vhe/switch.c | 44 +++++++++++++++++++++++++++++++++ 2 files changed, 47 insertions(+), 26 deletions(-) diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c index 2d80e81ae650..63a74c0330f1 100644 --- a/arch/arm64/kvm/emulate-nested.c +++ b/arch/arm64/kvm/emulate-nested.c @@ -2172,8 +2172,7 @@ static u64 kvm_check_illegal_exception_return(struct kvm_vcpu *vcpu, u64 spsr) void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu) { - u64 spsr, elr, mode; - bool direct_eret; + u64 spsr, elr; /* * Forward this trap to the virtual EL2 if the virtual @@ -2182,33 +2181,11 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu) if (forward_traps(vcpu, HCR_NV)) return; - /* - * Going through the whole put/load motions is a waste of time - * if this is a VHE guest hypervisor returning to its own - * userspace, or the hypervisor performing a local exception - * return. No need to save/restore registers, no need to - * switch S2 MMU. Just do the canonical ERET. - */ - spsr = vcpu_read_sys_reg(vcpu, SPSR_EL2); - spsr = kvm_check_illegal_exception_return(vcpu, spsr); - - mode = spsr & (PSR_MODE_MASK | PSR_MODE32_BIT); - - direct_eret = (mode == PSR_MODE_EL0t && - vcpu_el2_e2h_is_set(vcpu) && - vcpu_el2_tge_is_set(vcpu)); - direct_eret |= (mode == PSR_MODE_EL2h || mode == PSR_MODE_EL2t); - - if (direct_eret) { - *vcpu_pc(vcpu) = vcpu_read_sys_reg(vcpu, ELR_EL2); - *vcpu_cpsr(vcpu) = spsr; - trace_kvm_nested_eret(vcpu, *vcpu_pc(vcpu), spsr); - return; - } - preempt_disable(); kvm_arch_vcpu_put(vcpu); + spsr = __vcpu_sys_reg(vcpu, SPSR_EL2); + spsr = kvm_check_illegal_exception_return(vcpu, spsr); elr = __vcpu_sys_reg(vcpu, ELR_EL2); trace_kvm_nested_eret(vcpu, elr, spsr); diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c index 29f59c374f7a..0c175516d114 100644 --- a/arch/arm64/kvm/hyp/vhe/switch.c +++ b/arch/arm64/kvm/hyp/vhe/switch.c @@ -205,6 +205,49 @@ void kvm_vcpu_put_vhe(struct kvm_vcpu *vcpu) __vcpu_put_switch_sysregs(vcpu); } +static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code) +{ + u64 spsr, mode; + + /* + * Going through the whole put/load motions is a waste of time + * if this is a VHE guest hypervisor returning to its own + * userspace, or the hypervisor performing a local exception + * return. No need to save/restore registers, no need to + * switch S2 MMU. Just do the canonical ERET. + * + * Unless the trap has to be forwarded further down the line, + * of course... + */ + if (__vcpu_sys_reg(vcpu, HCR_EL2) & HCR_NV) + return false; + + spsr = read_sysreg_el1(SYS_SPSR); + mode = spsr & (PSR_MODE_MASK | PSR_MODE32_BIT); + + switch (mode) { + case PSR_MODE_EL0t: + if (!(vcpu_el2_e2h_is_set(vcpu) && vcpu_el2_tge_is_set(vcpu))) + return false; + break; + case PSR_MODE_EL2t: + mode = PSR_MODE_EL1t; + break; + case PSR_MODE_EL2h: + mode = PSR_MODE_EL1h; + break; + default: + return false; + } + + spsr = (spsr & ~(PSR_MODE_MASK | PSR_MODE32_BIT)) | mode; + + write_sysreg_el2(spsr, SYS_SPSR); + write_sysreg_el2(read_sysreg_el1(SYS_ELR), SYS_ELR); + + return true; +} + static const exit_handler_fn hyp_exit_handlers[] = { [0 ... ESR_ELx_EC_MAX] = NULL, [ESR_ELx_EC_CP15_32] = kvm_hyp_handle_cp15_32, @@ -215,6 +258,7 @@ static const exit_handler_fn hyp_exit_handlers[] = { [ESR_ELx_EC_DABT_LOW] = kvm_hyp_handle_dabt_low, [ESR_ELx_EC_WATCHPT_LOW] = kvm_hyp_handle_watchpt_low, [ESR_ELx_EC_PAC] = kvm_hyp_handle_ptrauth, + [ESR_ELx_EC_ERET] = kvm_hyp_handle_eret, [ESR_ELx_EC_MOPS] = kvm_hyp_handle_mops, }; -- 2.39.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel