From mboxrd@z Thu Jan 1 00:00:00 1970 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 1EDCF225D0; Mon, 20 Nov 2023 13:11:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AmqACQRa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7AECC433C7; Mon, 20 Nov 2023 13:11:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700485861; bh=Br/kj0Vn+4hLI9ZQgSRNyujZTVGG2XeMTcdvl3gvXa0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AmqACQRaguiSNWTpnw9MSgzc2PqqaZA+OY6xePomlynIkJMD6Gv2pFDtTcYK0uWB5 begeyUdtrzPZy9+wul4+qPKC/I0aAcKOFGD96JEI/+uyq8/uQRUkDZAOQBvuTNIvJF O4N1GxBmw1su6ioF2TW5rL2o0rcYh+0cagbkhGgHPVApAJSqSX8NJV3ZzALxijfGGo imJ4P8/Ht1+n2ydqKm9ucFO+FiVptcmzKm2k6CSX4QR56KGwlnE3cEoyciTnGV5lP+ JSYsAPwjV8S0k2YXbL05WHBB6n6I9MXJGdvlkjCcr/BsdWYbo15ESSwQNhZV9CekIK xvgVAQt008+cA== 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 1r543I-00EjnU-1h; Mon, 20 Nov 2023 13:11:00 +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 , Darren Hart , Jintack Lim , Russell King , Miguel Luis , James Morse , Suzuki K Poulose , Oliver Upton , Zenghui Yu Subject: [PATCH v11 42/43] KVM: arm64: nv: Accelerate EL0 timer read accesses when FEAT_ECV is on Date: Mon, 20 Nov 2023 13:10:26 +0000 Message-Id: <20231120131027.854038-43-maz@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231120131027.854038-1-maz@kernel.org> References: <20231120131027.854038-1-maz@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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, darren@os.amperecomputing.com, jintack@cs.columbia.edu, rmk+kernel@armlinux.org.uk, miguel.luis@oracle.com, 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 Although FEAT_ECV allows us to correctly enable the timers, it also reduces performances pretty badly (a L2 guest doing a lot of virtio emulated in L1 userspace results in a 30% degradation). Mitigate this by emulating the CTL/CVAL register reads in the inner run loop, without returning to the general kernel. This halves the overhead described above. Signed-off-by: Marc Zyngier --- arch/arm64/kvm/arch_timer.c | 15 ------- arch/arm64/kvm/hyp/vhe/switch.c | 70 +++++++++++++++++++++++++++++++++ include/kvm/arm_arch_timer.h | 15 +++++++ 3 files changed, 85 insertions(+), 15 deletions(-) diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c index 860f6e190e63..1ee1ede23607 100644 --- a/arch/arm64/kvm/arch_timer.c +++ b/arch/arm64/kvm/arch_timer.c @@ -101,21 +101,6 @@ u64 timer_get_cval(struct arch_timer_context *ctxt) } } -static u64 timer_get_offset(struct arch_timer_context *ctxt) -{ - u64 offset = 0; - - if (!ctxt) - return 0; - - if (ctxt->offset.vm_offset) - offset += *ctxt->offset.vm_offset; - if (ctxt->offset.vcpu_offset) - offset += *ctxt->offset.vcpu_offset; - - return offset; -} - static void timer_set_ctl(struct arch_timer_context *ctxt, u32 ctl) { struct kvm_vcpu *vcpu = ctxt->vcpu; diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c index 360328aaaf7c..8d1e9d1adabe 100644 --- a/arch/arm64/kvm/hyp/vhe/switch.c +++ b/arch/arm64/kvm/hyp/vhe/switch.c @@ -258,11 +258,81 @@ static bool kvm_hyp_handle_tlbi_el1(struct kvm_vcpu *vcpu, u64 *exit_code) return true; } +static bool kvm_hyp_handle_timer(struct kvm_vcpu *vcpu, u64 *exit_code) +{ + u64 esr, val; + + /* + * Having FEAT_ECV allows for a better quality of timer emulation. + * However, this comes at a huge cost in terms of traps. Try and + * satisfy the reads without returning to the kernel if we can. + */ + if (!is_hyp_ctxt(vcpu)) + return false; + + esr = kvm_vcpu_get_esr(vcpu); + if ((esr & ESR_ELx_SYS64_ISS_DIR_MASK) != ESR_ELx_SYS64_ISS_DIR_READ) + return false; + + switch (esr_sys64_to_sysreg(esr)) { + case SYS_CNTP_CTL_EL02: + val = __vcpu_sys_reg(vcpu, CNTP_CTL_EL0); + break; + case SYS_CNTP_CTL_EL0: + if (vcpu_el2_e2h_is_set(vcpu)) + val = read_sysreg_el0(SYS_CNTP_CTL); + else + val = __vcpu_sys_reg(vcpu, CNTP_CTL_EL0); + break; + case SYS_CNTP_CVAL_EL02: + val = __vcpu_sys_reg(vcpu, CNTP_CVAL_EL0); + break; + case SYS_CNTP_CVAL_EL0: + if (vcpu_el2_e2h_is_set(vcpu)) { + val = read_sysreg_el0(SYS_CNTP_CVAL); + + if (!has_cntpoff()) + val -= timer_get_offset(vcpu_hptimer(vcpu)); + } else { + val = __vcpu_sys_reg(vcpu, CNTP_CVAL_EL0); + } + break; + case SYS_CNTV_CTL_EL02: + val = __vcpu_sys_reg(vcpu, CNTV_CTL_EL0); + break; + case SYS_CNTV_CTL_EL0: + if (vcpu_el2_e2h_is_set(vcpu)) + val = read_sysreg_el0(SYS_CNTV_CTL); + else + val = __vcpu_sys_reg(vcpu, CNTV_CTL_EL0); + break; + case SYS_CNTV_CVAL_EL02: + val = __vcpu_sys_reg(vcpu, CNTV_CVAL_EL0); + break; + case SYS_CNTV_CVAL_EL0: + if (vcpu_el2_e2h_is_set(vcpu)) + val = read_sysreg_el0(SYS_CNTV_CVAL); + else + val = __vcpu_sys_reg(vcpu, CNTV_CVAL_EL0); + break; + default: + return false; + } + + vcpu_set_reg(vcpu, kvm_vcpu_sys_get_rt(vcpu), val); + __kvm_skip_instr(vcpu); + + return true; +} + static bool kvm_hyp_handle_sysreg_vhe(struct kvm_vcpu *vcpu, u64 *exit_code) { if (kvm_hyp_handle_tlbi_el1(vcpu, exit_code)) return true; + if (kvm_hyp_handle_timer(vcpu, exit_code)) + return true; + return kvm_hyp_handle_sysreg(vcpu, exit_code); } diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h index 6e3f6b7ff2b2..c1ba31fab6f5 100644 --- a/include/kvm/arm_arch_timer.h +++ b/include/kvm/arm_arch_timer.h @@ -156,4 +156,19 @@ static inline bool has_cntpoff(void) return (has_vhe() && cpus_have_final_cap(ARM64_HAS_ECV_CNTPOFF)); } +static inline u64 timer_get_offset(struct arch_timer_context *ctxt) +{ + u64 offset = 0; + + if (!ctxt) + return 0; + + if (ctxt->offset.vm_offset) + offset += *ctxt->offset.vm_offset; + if (ctxt->offset.vcpu_offset) + offset += *ctxt->offset.vcpu_offset; + + return offset; +} + #endif -- 2.39.2