From patchwork Tue Jan 31 09:25:01 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 13122661 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DE791C636CC for ; Tue, 31 Jan 2023 09:41:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232501AbjAaJl6 (ORCPT ); Tue, 31 Jan 2023 04:41:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229686AbjAaJl5 (ORCPT ); Tue, 31 Jan 2023 04:41:57 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A646142BE7 for ; Tue, 31 Jan 2023 01:41:33 -0800 (PST) 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 ams.source.kernel.org (Postfix) with ESMTPS id 144D2B81AF7 for ; Tue, 31 Jan 2023 09:41:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B349DC433D2; Tue, 31 Jan 2023 09:41:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1675158090; bh=C193qCDjqiF5HkfsJlWly9Jsvkj9TvtpD7IYpBzHGpI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uNYz1SAYLmOJCe+uWcBDN+NDEqD/VQmLamiThqyte4jsBwE6JCNo8x/VBrn2dnqAb IZsgQ+L3E9T2jpkXkLhU0Faja2IOxeYREguEcohp0ccr79RLc00IFkZLr3VOyJzq+F iL1+x0xVGdH7ky8Yfj2f1W+JReZ7XKdMqIf1j0elslU16lJdVRHs5t89jEYmlUxPys w3BbJ9/46vSL0pNGEuAw8ryX3GiBdspCryUtx7S8Xf9MO+xKvLx8ogtT/xBLgo9KNn drUWEr9aaDEx0bOX9hgK8u5irfRlLWH1Jmrhrstapb+TWwKq6VaBXpSwpF15oD15NC lLiGFyOY61NAQ== 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 1pMmtw-0067U2-U8; Tue, 31 Jan 2023 09:26:04 +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 v8 66/69] KVM: arm64: nv: Fast-track 'InHost' exception returns Date: Tue, 31 Jan 2023 09:25:01 +0000 Message-Id: <20230131092504.2880505-67-maz@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230131092504.2880505-1-maz@kernel.org> References: <20230131092504.2880505-1-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 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.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)