From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) (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 9141986337 for ; Thu, 19 Dec 2024 22:41:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734648117; cv=none; b=eNoAIUOqwC4Vgu2hivVIqhQgeSPjDlgcRxqk7xVq5Z5wcV85ljxTxlk9BjFe2AI5ebSvVpQIFHRF1+inl3FoAK5GkTSEuW0ScJFqxXH/Z4RwiaQPFeMZh/KCIIoNGy8cPSYw/g2i/uXEjfvomy8u6j2RBFcWq+CMNKNploHnV8g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734648117; c=relaxed/simple; bh=1m1OTV3Z07RpGR1gYQrzdXd/7n+wC8cTrlthjxMut4s=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=QAEiAUJoiapj2O+YZMcWPekh9J5hOeqQr3AqMIoY3cM9fDPPdC06JnpQ99Y4PJBKPE5qCMaskbEBmVDNp46jCZSjPAM+cAtMxIdHCk17U0lHin1Aj3yGA/64kWUx2/yPRsnIv1Cl9mBhI2ZzUOpJAeGLg2MqmWyKiAaN4BVyTjk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=GatuqOr/; arc=none smtp.client-ip=95.215.58.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="GatuqOr/" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1734648114; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iX7TAsD+9g0v/Xv15OsbwtzCwaftrrm19PwNqMUkgQI=; b=GatuqOr/79Miv+A1Av08XbiNT8CxmCBwooB2A7kRFvnhAQl3nXoTeMVMy3yFIgMzd9/1bM sN1Q5546BONG2iRAWBDckpOwLk4txFOiWlB2bnWuDrLYDxGkiJwiPeJOOiLrn8sKlBpxUB 68i+J0CQaJScQtXzKga2dlTNdPIp+Ss= From: Oliver Upton To: kvmarm@lists.linux.dev Cc: Marc Zyngier , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Mingwei Zhang , Colton Lewis , Raghavendra Rao Ananta , James Clark , Oliver Upton Subject: [PATCH v4 11/19] KVM: arm64: Use debug_owner to track if debug regs need save/restore Date: Thu, 19 Dec 2024 14:41:08 -0800 Message-Id: <20241219224116.3941496-12-oliver.upton@linux.dev> In-Reply-To: <20241219224116.3941496-1-oliver.upton@linux.dev> References: <20241219224116.3941496-1-oliver.upton@linux.dev> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Use the debug owner to determine if the debug regs are in use instead of keeping around the DEBUG_DIRTY flag. Debug registers are now saved/restored after the first trap, regardless of whether it was a read or a write. This also shifts the point at which KVM becomes lazy to vcpu_put() rather than the next exception taken from the guest. Tested-by: James Clark Signed-off-by: Oliver Upton --- arch/arm64/include/asm/kvm_host.h | 4 +-- arch/arm64/kvm/debug.c | 19 ++----------- arch/arm64/kvm/hyp/include/hyp/debug-sr.h | 2 -- arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 4 +-- arch/arm64/kvm/sys_regs.c | 33 ---------------------- 5 files changed, 7 insertions(+), 55 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 905b84e59c24..a6796a952af7 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -917,8 +917,6 @@ struct kvm_vcpu_arch { #define EXCEPT_AA64_EL2_IRQ __vcpu_except_flags(5) #define EXCEPT_AA64_EL2_FIQ __vcpu_except_flags(6) #define EXCEPT_AA64_EL2_SERR __vcpu_except_flags(7) -/* Guest debug is live */ -#define DEBUG_DIRTY __vcpu_single_flag(iflags, BIT(4)) /* Physical CPU not in supported_cpus */ #define ON_UNSUPPORTED_CPU __vcpu_single_flag(sflags, BIT(0)) @@ -1356,6 +1354,8 @@ void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu); ((vcpu)->arch.debug_owner != VCPU_DEBUG_FREE) #define kvm_host_owns_debug_regs(vcpu) \ ((vcpu)->arch.debug_owner == VCPU_DEBUG_HOST_OWNED) +#define kvm_guest_owns_debug_regs(vcpu) \ + ((vcpu)->arch.debug_owner == VCPU_DEBUG_GUEST_OWNED) int kvm_arm_vcpu_arch_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr); diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index c75874435157..300ea3720bed 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -86,15 +86,9 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu) vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; /* - * Trap debug register access when one of the following is true: - * - Userspace is using the hardware to debug the guest - * (KVM_GUESTDBG_USE_HW is set). - * - The guest is not using debug (DEBUG_DIRTY clear). - * - The guest has enabled the OS Lock (debug exceptions are blocked). + * Trap debug registers if the guest doesn't have ownership of them. */ - if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) || - !vcpu_get_flag(vcpu, DEBUG_DIRTY) || - kvm_vcpu_os_lock_enabled(vcpu)) + if (!kvm_guest_owns_debug_regs(vcpu)) vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; /* Write MDCR_EL2 directly if we're already at EL2 */ @@ -127,8 +121,7 @@ void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu) * debug related registers. * * Additionally, KVM only traps guest accesses to the debug registers if - * the guest is not actively using them (see the DEBUG_DIRTY - * flag on vcpu->arch.iflags). Since the guest must not interfere + * the guest is not actively using them. Since the guest must not interfere * with the hardware state when debugging the guest, we must ensure that * trapping is enabled whenever we are debugging the guest using the * debug registers. @@ -197,8 +190,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) mdscr |= DBG_MDSCR_MDE; vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); - vcpu_set_flag(vcpu, DEBUG_DIRTY); - /* * The OS Lock blocks debug exceptions in all ELs when it is * enabled. If the guest has enabled the OS Lock, constrain its @@ -213,10 +204,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1); } } - - /* If KDE or MDE are set, perform a full save/restore cycle. */ - if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE)) - vcpu_set_flag(vcpu, DEBUG_DIRTY); } void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) diff --git a/arch/arm64/kvm/hyp/include/hyp/debug-sr.h b/arch/arm64/kvm/hyp/include/hyp/debug-sr.h index 9e3051225039..c14586d87361 100644 --- a/arch/arm64/kvm/hyp/include/hyp/debug-sr.h +++ b/arch/arm64/kvm/hyp/include/hyp/debug-sr.h @@ -176,8 +176,6 @@ static inline void __debug_switch_to_host_common(struct kvm_vcpu *vcpu) __debug_save_state(guest_dbg, guest_ctxt); __debug_restore_state(host_dbg, host_ctxt); - - vcpu_clear_flag(vcpu, DEBUG_DIRTY); } #endif /* __ARM64_KVM_HYP_DEBUG_SR_H__ */ diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h index a651c43ad679..a998b2f6abcb 100644 --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h @@ -283,7 +283,7 @@ static inline void __sysreg32_save_state(struct kvm_vcpu *vcpu) __vcpu_sys_reg(vcpu, DACR32_EL2) = read_sysreg(dacr32_el2); __vcpu_sys_reg(vcpu, IFSR32_EL2) = read_sysreg(ifsr32_el2); - if (has_vhe() || vcpu_get_flag(vcpu, DEBUG_DIRTY)) + if (has_vhe() || kvm_debug_regs_in_use(vcpu)) __vcpu_sys_reg(vcpu, DBGVCR32_EL2) = read_sysreg(dbgvcr32_el2); } @@ -300,7 +300,7 @@ static inline void __sysreg32_restore_state(struct kvm_vcpu *vcpu) write_sysreg(__vcpu_sys_reg(vcpu, DACR32_EL2), dacr32_el2); write_sysreg(__vcpu_sys_reg(vcpu, IFSR32_EL2), ifsr32_el2); - if (has_vhe() || vcpu_get_flag(vcpu, DEBUG_DIRTY)) + if (has_vhe() || kvm_debug_regs_in_use(vcpu)) write_sysreg(__vcpu_sys_reg(vcpu, DBGVCR32_EL2), dbgvcr32_el2); } diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 8c5771572133..66db77fb6201 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -621,40 +621,11 @@ static bool trap_dbgauthstatus_el1(struct kvm_vcpu *vcpu, } } -/* - * We want to avoid world-switching all the DBG registers all the - * time: - * - * - If we've touched any debug register, it is likely that we're - * going to touch more of them. It then makes sense to disable the - * traps and start doing the save/restore dance - * - If debug is active (DBG_MDSCR_KDE or DBG_MDSCR_MDE set), it is - * then mandatory to save/restore the registers, as the guest - * depends on them. - * - * For this, we use a DIRTY bit, indicating the guest has modified the - * debug registers, used as follow: - * - * On guest entry: - * - If the dirty bit is set (because we're coming back from trapping), - * disable the traps, save host registers, restore guest registers. - * - If debug is actively in use (DBG_MDSCR_KDE or DBG_MDSCR_MDE set), - * set the dirty bit, disable the traps, save host registers, - * restore guest registers. - * - Otherwise, enable the traps - * - * On guest exit: - * - If the dirty bit is set, save guest registers, restore host - * registers and clear the dirty bit. This ensure that the host can - * now use the debug registers. - */ static bool trap_debug_regs(struct kvm_vcpu *vcpu, struct sys_reg_params *p, const struct sys_reg_desc *r) { access_rw(vcpu, p, r); - if (p->is_write) - vcpu_set_flag(vcpu, DEBUG_DIRTY); kvm_debug_set_guest_ownership(vcpu); return true; @@ -665,9 +636,6 @@ static bool trap_debug_regs(struct kvm_vcpu *vcpu, * * A 32 bit write to a debug register leave top bits alone * A 32 bit read from a debug register only returns the bottom bits - * - * All writes will set the DEBUG_DIRTY flag to ensure the hyp code - * switches between host and guest values in future. */ static void reg_to_dbg(struct kvm_vcpu *vcpu, struct sys_reg_params *p, @@ -684,7 +652,6 @@ static void reg_to_dbg(struct kvm_vcpu *vcpu, *dbg_reg = val; kvm_debug_set_guest_ownership(vcpu); - vcpu_set_flag(vcpu, DEBUG_DIRTY); } static void dbg_to_reg(struct kvm_vcpu *vcpu, -- 2.39.5