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 239F51C1AAA; Tue, 12 Aug 2025 19:01:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755025318; cv=none; b=f2c+8TfmNOpmrCoTstl6gh6gGmFVa1VHEgcb7FjAhoCJuXMVqdyAp9q1BWhlebK+eXWSfpobritn8vSTR3dykpGzFD2nEZp27q75/b/+SY88h9eMjFT3PfN2Tt3Q+31AoRisM5Ep+LFGvWCJkHtPgXSLIzrDr/WrvURD8HxFPPo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755025318; c=relaxed/simple; bh=XFvHuM+wfMiT3qN2HKoJvCS+1XaHH0nv5a2Fn9swdkQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Z/RbXdXCCBK/23d9/rcK0UPKtLbSR9qh5s39lpZnWqHFAc1Ccksdef2yDgsoQ5lpCOg8U//QkfTyIUUbDhYq9gRgg84JSULvw8auxCw48XqdX+LhKaI5N3SbXy3C/yz+DO4x+ItRjpZyr8zyCbIJcWz5jyz20Jr+Jyc0rMUtsSo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=APkv3Sp0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="APkv3Sp0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A967C4CEF0; Tue, 12 Aug 2025 19:01:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755025317; bh=XFvHuM+wfMiT3qN2HKoJvCS+1XaHH0nv5a2Fn9swdkQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=APkv3Sp0ViPVX/RjKdFPhU7af7uCL+lkLV6zdigSlh6fdQ4yJcoc1h2sl3RaDa0+/ bPV8RKEgipUgFWQPiOEg7D7VyHr7v7eSr7a5U4fSVC5ZNx84t3EafnOR7G5FcIqyiS kUU30SiimrEH4nuG5Cuu3GNbOpTSbaemCSWdgTgI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sean Christopherson Subject: [PATCH 6.16 605/627] KVM: x86: Drop kvm_x86_ops.set_dr6() in favor of a new KVM_RUN flag Date: Tue, 12 Aug 2025 19:35:00 +0200 Message-ID: <20250812173454.891102768@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250812173419.303046420@linuxfoundation.org> References: <20250812173419.303046420@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sean Christopherson commit 80c64c7afea1da6a93ebe88d3d29d8a60377ef80 upstream. Instruct vendor code to load the guest's DR6 into hardware via a new KVM_RUN flag, and remove kvm_x86_ops.set_dr6(), whose sole purpose was to load vcpu->arch.dr6 into hardware when DR6 can be read/written directly by the guest. Note, TDX already WARNs on any run_flag being set, i.e. will yell if KVM thinks DR6 needs to be reloaded. TDX vCPUs force KVM_DEBUGREG_AUTO_SWITCH and never clear the flag, i.e. should never observe KVM_RUN_LOAD_GUEST_DR6. Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250610232010.162191-4-seanjc@google.com Signed-off-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/kvm-x86-ops.h | 1 - arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/svm/svm.c | 12 +++++++----- arch/x86/kvm/vmx/main.c | 9 --------- arch/x86/kvm/vmx/vmx.c | 9 +++------ arch/x86/kvm/x86.c | 2 +- 6 files changed, 12 insertions(+), 23 deletions(-) --- a/arch/x86/include/asm/kvm-x86-ops.h +++ b/arch/x86/include/asm/kvm-x86-ops.h @@ -49,7 +49,6 @@ KVM_X86_OP(set_idt) KVM_X86_OP(get_gdt) KVM_X86_OP(set_gdt) KVM_X86_OP(sync_dirty_debug_regs) -KVM_X86_OP(set_dr6) KVM_X86_OP(set_dr7) KVM_X86_OP(cache_reg) KVM_X86_OP(get_rflags) --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1682,6 +1682,7 @@ static inline u16 kvm_lapic_irq_dest_mod enum kvm_x86_run_flags { KVM_RUN_FORCE_IMMEDIATE_EXIT = BIT(0), + KVM_RUN_LOAD_GUEST_DR6 = BIT(1), }; struct kvm_x86_ops { @@ -1734,7 +1735,6 @@ struct kvm_x86_ops { void (*get_gdt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt); void (*set_gdt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt); void (*sync_dirty_debug_regs)(struct kvm_vcpu *vcpu); - void (*set_dr6)(struct kvm_vcpu *vcpu, unsigned long value); void (*set_dr7)(struct kvm_vcpu *vcpu, unsigned long value); void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg); unsigned long (*get_rflags)(struct kvm_vcpu *vcpu); --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4438,10 +4438,13 @@ static __no_kcsan fastpath_t svm_vcpu_ru svm_hv_update_vp_id(svm->vmcb, vcpu); /* - * Run with all-zero DR6 unless needed, so that we can get the exact cause - * of a #DB. - */ - if (likely(!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT))) + * Run with all-zero DR6 unless the guest can write DR6 freely, so that + * KVM can get the exact cause of a #DB. Note, loading guest DR6 from + * KVM's snapshot is only necessary when DR accesses won't exit. + */ + if (unlikely(run_flags & KVM_RUN_LOAD_GUEST_DR6)) + svm_set_dr6(vcpu, vcpu->arch.dr6); + else if (likely(!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT))) svm_set_dr6(vcpu, DR6_ACTIVE_LOW); clgi(); @@ -5252,7 +5255,6 @@ static struct kvm_x86_ops svm_x86_ops __ .set_idt = svm_set_idt, .get_gdt = svm_get_gdt, .set_gdt = svm_set_gdt, - .set_dr6 = svm_set_dr6, .set_dr7 = svm_set_dr7, .sync_dirty_debug_regs = svm_sync_dirty_debug_regs, .cache_reg = svm_cache_reg, --- a/arch/x86/kvm/vmx/main.c +++ b/arch/x86/kvm/vmx/main.c @@ -489,14 +489,6 @@ static void vt_set_gdt(struct kvm_vcpu * vmx_set_gdt(vcpu, dt); } -static void vt_set_dr6(struct kvm_vcpu *vcpu, unsigned long val) -{ - if (is_td_vcpu(vcpu)) - return; - - vmx_set_dr6(vcpu, val); -} - static void vt_set_dr7(struct kvm_vcpu *vcpu, unsigned long val) { if (is_td_vcpu(vcpu)) @@ -943,7 +935,6 @@ struct kvm_x86_ops vt_x86_ops __initdata .set_idt = vt_op(set_idt), .get_gdt = vt_op(get_gdt), .set_gdt = vt_op(set_gdt), - .set_dr6 = vt_op(set_dr6), .set_dr7 = vt_op(set_dr7), .sync_dirty_debug_regs = vt_op(sync_dirty_debug_regs), .cache_reg = vt_op(cache_reg), --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5606,12 +5606,6 @@ void vmx_sync_dirty_debug_regs(struct kv set_debugreg(DR6_RESERVED, 6); } -void vmx_set_dr6(struct kvm_vcpu *vcpu, unsigned long val) -{ - lockdep_assert_irqs_disabled(); - set_debugreg(vcpu->arch.dr6, 6); -} - void vmx_set_dr7(struct kvm_vcpu *vcpu, unsigned long val) { vmcs_writel(GUEST_DR7, val); @@ -7370,6 +7364,9 @@ fastpath_t vmx_vcpu_run(struct kvm_vcpu vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]); vcpu->arch.regs_dirty = 0; + if (run_flags & KVM_RUN_LOAD_GUEST_DR6) + set_debugreg(vcpu->arch.dr6, 6); + /* * Refresh vmcs.HOST_CR3 if necessary. This must be done immediately * prior to VM-Enter, as the kernel may load a new ASID (PCID) any time --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11052,7 +11052,7 @@ static int vcpu_enter_guest(struct kvm_v set_debugreg(vcpu->arch.eff_db[3], 3); /* When KVM_DEBUGREG_WONT_EXIT, dr6 is accessible in guest. */ if (unlikely(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT)) - kvm_x86_call(set_dr6)(vcpu, vcpu->arch.dr6); + run_flags |= KVM_RUN_LOAD_GUEST_DR6; } else if (unlikely(hw_breakpoint_active())) { set_debugreg(DR7_FIXED_1, 7); }