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 2ABF0C71132 for ; Thu, 12 Jan 2023 20:06:06 +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=fMcclAvqJTp43dQ+yc53LJd/lWoQs7i1Pk+NJMwQc54=; b=TOfokgt7dVWRP+ h2YfrgPrYQtyQxnsjW8ygrkLsifCNUyrem+uRy38UxcL7RHJhPPZWZ4SdkvxTkBJLECzL48fRebOT 8NhoTgz4wmhZAE12yNtu8nfRoSuUv3YaRziqQYxsg/5GcYDTXrpdCIdr7FK/kJM99X+/K171OQYsA DIgEIflVMDmLUsWaPltvfCH2lV1fDA6+nnhTHQDYmU2YUpY7Tmyylrg4rfQukj2nl58FnsxQ7DL91 IIk77Yd926vJFULTnVtKeXnYViAPmj785DDWM2gmHrWP0kudmH/pH3dlvaGCRzE2p3lI/ZsKqfbEL mkLBFTspFx7w9s9RqL7A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pG3oa-00GkLE-Ji; Thu, 12 Jan 2023 20:04:46 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pG3A5-00GS2z-FR for linux-arm-kernel@lists.infradead.org; Thu, 12 Jan 2023 19:22:55 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 15F0460A47; Thu, 12 Jan 2023 19:22:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A32AC433EF; Thu, 12 Jan 2023 19:22:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673551372; bh=C193qCDjqiF5HkfsJlWly9Jsvkj9TvtpD7IYpBzHGpI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MbrSej1yGiejo+gENfW4uJdBsq1FHqLB94c6jucYEavWNBUveRNf/NN/+ssnWNIlG tHCkajF+FB8L48H5QIXpwx/O4pK1/HY2bJ3pouoKUIKhLDMeVLFUgI6n/W6RVdy7VJ 5Cs89AHVP6+4mIFWysBytuyZ3Bo+HF53G8kLWHSB/iWLikQgZYiSt+9hCS9Iz/qMdM AbmTXAfTAEunV823CMkO9HamVD8Agawmb053c5qliIjr8BUSEzW3KrE8trt7mA/8W5 HbhMh3X0Js92Jt08RA07MyzXkFS5VsSAm/k+jjQsfwm4SenHUL4EY4szePj6r+4dCz 89Zs2zEEcdwIw== 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 1pG37T-001IWu-Sw; Thu, 12 Jan 2023 19:20:11 +0000 From: Marc Zyngier To: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Alexandru Elisei , Andre Przywara , Chase Conklin , Christoffer Dall , Ganapatrao Kulkarni , Jintack Lim , Russell King , James Morse , Suzuki K Poulose , Oliver Upton , Zenghui Yu Subject: [PATCH v7 65/68] KVM: arm64: nv: Fast-track 'InHost' exception returns Date: Thu, 12 Jan 2023 19:19:24 +0000 Message-Id: <20230112191927.1814989-66-maz@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230112191927.1814989-1-maz@kernel.org> References: <20230112191927.1814989-1-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, alexandru.elisei@arm.com, andre.przywara@arm.com, chase.conklin@arm.com, christoffer.dall@arm.com, gankulkarni@os.amperecomputing.com, jintack@cs.columbia.edu, rmk+kernel@armlinux.org.uk, james.morse@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, yuzenghui@huawei.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-20230112_112253_627960_57EDCDEB X-CRM114-Status: GOOD ( 21.68 ) 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 ARMv8.3-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 | 46 +++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+), 26 deletions(-) diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c index 555771e1260d..e2d23f624115 100644 --- a/arch/arm64/kvm/emulate-nested.c +++ b/arch/arm64/kvm/emulate-nested.c @@ -79,8 +79,7 @@ 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 @@ -89,33 +88,11 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu) if (forward_nv_traps(vcpu)) 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 7682d2f13eaa..238c6613cf47 100644 --- a/arch/arm64/kvm/hyp/vhe/switch.c +++ b/arch/arm64/kvm/hyp/vhe/switch.c @@ -168,6 +168,51 @@ void deactivate_traps_vhe_put(struct kvm_vcpu *vcpu) __deactivate_traps_common(vcpu); } +static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code) +{ + struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt; + 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); + spsr = __fixup_spsr_el2_read(ctxt, 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, @@ -177,6 +222,7 @@ static const exit_handler_fn hyp_exit_handlers[] = { [ESR_ELx_EC_IABT_LOW] = kvm_hyp_handle_iabt_low, [ESR_ELx_EC_DABT_LOW] = kvm_hyp_handle_dabt_low, [ESR_ELx_EC_PAC] = kvm_hyp_handle_ptrauth, + [ESR_ELx_EC_ERET] = kvm_hyp_handle_eret, }; static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu) -- 2.34.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel