From nobody Sat Oct 4 16:20:47 2025 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 60DF4189F43 for ; Fri, 15 Aug 2025 00:57:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755219455; cv=none; b=H8YnT+TbUmw5uTr5sOrxaR77CpWkbLUNPlyoaneXYmw7aYApnuGZspqCKnMqlUum+PbFgabp5/OO1ycnIWrvq5jz9hQMhkhrgCffzTNKQ0z9V7w69jA5CJJNOB2CGIoloIhZNjjaWoaLp7jtW+dAraIjmOXy8NuRujjmEyrBAIM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755219455; c=relaxed/simple; bh=CEVBW4WVbt8Lnu/3tYJRzLW233Zr94AiOicIUItOI/c=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Q1n1hLuyD6m2N8Ow8Cuy18xIN2VKcWUGxeIhnBb7XVvUAsOOYLJTZPfOzmn7RQw37BLoy1OrRUMtgQ1TEnNRZWe0i00kwDbLSzua5dDSP8B+jefD0dczBrBCy4yf0SwkFnK6C0Ht6slzxQhzEfsnccz3zoORZ/cBKbfqEXpLd7s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=W9UJZWLA; arc=none smtp.client-ip=209.85.214.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="W9UJZWLA" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-244581950a1so17529685ad.2 for ; Thu, 14 Aug 2025 17:57:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1755219453; x=1755824253; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=0uUsJ4w557iIRI1+Xq47LADMF7Kam5FO29De9FYVnNM=; b=W9UJZWLAJNI+BfwSzOJ62BgM/aTO8sA/dxQh7bz56/fg3qH5m+bKaV2Cci5Lav638t 2KZhvZHFRIsyXXoAwrMrTM9lCXfX9NlW3wAuBqeTffg5jed2TlE7MerMlIyMQeVBpw8J AlneuABJ7PceUJNHNJcYjiuvN/LHYGxctmicVcm9FRcEZ+VlFqa4lpt7Q0y9H1W5D3+t xBjzR9YGjx4VWm+bluVzYTazO+/133a0SZXVenRDShJpTcDjxDUUPqRoO2omaIn2n22+ XlQb6AHzj4AT1jWHzH80TMbglu2h8UOc9apBJi/oRtxQF8PgNdYVgCKwasCunJnlLGOq 0j+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1755219453; x=1755824253; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=0uUsJ4w557iIRI1+Xq47LADMF7Kam5FO29De9FYVnNM=; b=gXc7e+tQOMupdmbMJ1FTmp+8K/jRt1P+BFFw420fzAWjGd9S52+3BXrpwvKKxmAa09 zde5M/EVJRGK01/gV/hvAydIie2IYQKaNCdu62XQSU6pRobQRXYUfTQYFESgREICR++v XQSx8lEvLOpm9QntYS2cAaNENLThoRI8UgXginSR5NgLWt6GSRXVHMGjzS/9EbGiFpAV JxgI/M2Mdutr2Zl+Wg6o29MCbKvRZRzNa0cNXEbhrGk+dVfx8f1VWayPED0/2JuEZ06/ AEkgXRBZeJ7gGi8KdKamSLk6G9HFULwSRfA+a1nVxGuiVUMQ+N8QO5nhPuCbfUd5IsaO g03A== X-Forwarded-Encrypted: i=1; AJvYcCVHjJWBp9RSJ0hNUr7mSClclg+M2sfSngTRW3vgRF/1KBcUEZ6Wevth9zNbTgj2sE7w4+3jYO2U2ZgxmxE=@vger.kernel.org X-Gm-Message-State: AOJu0Yxq0pqaLsKQtkObnicSXkFqMuRXKib6K+35UziL9wudS4kVwu0b f4rKsgL0w/8/UO74/I1w5CtVcVzUreWoz7g27jB6ikeELm4k4k8MW07pCIVAWC9+IQMYPfpehi1 BdJFBnw== X-Google-Smtp-Source: AGHT+IFWenSfmvpmGV9Uvy5VzE86vLvZMuLNMRdB3X6t/lZx2YcZPhmYgNcEp3Mb/9LKOQ1XlpftJN6lvyM= X-Received: from pjbqc5.prod.google.com ([2002:a17:90b:2885:b0:31c:4a51:8b75]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:e84b:b0:240:5523:6658 with SMTP id d9443c01a7336-2446d89d22cmr3619125ad.29.1755219452737; Thu, 14 Aug 2025 17:57:32 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 14 Aug 2025 17:57:20 -0700 In-Reply-To: <20250815005725.2386187-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250815005725.2386187-1-seanjc@google.com> X-Mailer: git-send-email 2.51.0.rc1.163.g2494970778-goog Message-ID: <20250815005725.2386187-3-seanjc@google.com> Subject: [PATCH 6.12.y 2/7] KVM: x86: Drop kvm_x86_ops.set_dr6() in favor of a new KVM_RUN flag From: Sean Christopherson To: stable@vger.kernel.org, Greg Kroah-Hartman , Sasha Levin Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" [ Upstream commit 80c64c7afea1da6a93ebe88d3d29d8a60377ef80 ] 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 [sean: drop TDX changes] Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm-x86-ops.h | 1 - arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/svm/svm.c | 10 ++++++---- arch/x86/kvm/vmx/main.c | 1 - arch/x86/kvm/vmx/vmx.c | 9 +++------ arch/x86/kvm/x86.c | 2 +- 6 files changed, 11 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-= x86-ops.h index cfb22f8c451a..861d080ed4c6 100644 --- a/arch/x86/include/asm/kvm-x86-ops.h +++ b/arch/x86/include/asm/kvm-x86-ops.h @@ -47,7 +47,6 @@ 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) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_hos= t.h index cccc8cbe72db..2ed05925d9d5 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1629,6 +1629,7 @@ static inline u16 kvm_lapic_irq_dest_mode(bool dest_m= ode_logical) =20 enum kvm_x86_run_flags { KVM_RUN_FORCE_IMMEDIATE_EXIT =3D BIT(0), + KVM_RUN_LOAD_GUEST_DR6 =3D BIT(1), }; =20 struct kvm_x86_ops { @@ -1679,7 +1680,6 @@ 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); diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 7d1b871cfc02..800f781475c0 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4270,10 +4270,13 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kv= m_vcpu *vcpu, u64 run_flags) svm_hv_update_vp_id(svm->vmcb, vcpu); =20 /* - * Run with all-zero DR6 unless needed, so that we can get the exact cause - * of a #DB. + * 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 (likely(!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_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); =20 clgi(); @@ -5084,7 +5087,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata =3D { .set_idt =3D svm_set_idt, .get_gdt =3D svm_get_gdt, .set_gdt =3D svm_set_gdt, - .set_dr6 =3D svm_set_dr6, .set_dr7 =3D svm_set_dr7, .sync_dirty_debug_regs =3D svm_sync_dirty_debug_regs, .cache_reg =3D svm_cache_reg, diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c index 47476fcc179a..7668e2fb8043 100644 --- a/arch/x86/kvm/vmx/main.c +++ b/arch/x86/kvm/vmx/main.c @@ -60,7 +60,6 @@ struct kvm_x86_ops vt_x86_ops __initdata =3D { .set_idt =3D vmx_set_idt, .get_gdt =3D vmx_get_gdt, .set_gdt =3D vmx_set_gdt, - .set_dr6 =3D vmx_set_dr6, .set_dr7 =3D vmx_set_dr7, .sync_dirty_debug_regs =3D vmx_sync_dirty_debug_regs, .cache_reg =3D vmx_cache_reg, diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 2a977cdfcd0c..b9c7940feac6 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5630,12 +5630,6 @@ void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu) set_debugreg(DR6_RESERVED, 6); } =20 -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); @@ -7400,6 +7394,9 @@ fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, u64 ru= n_flags) vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]); vcpu->arch.regs_dirty =3D 0; =20 + 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 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 44ab46f2a2d2..7beea8fb6ea6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10977,7 +10977,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 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 |=3D KVM_RUN_LOAD_GUEST_DR6; } else if (unlikely(hw_breakpoint_active())) { set_debugreg(DR7_FIXED_1, 7); } --=20 2.51.0.rc1.163.g2494970778-goog