All of lore.kernel.org
 help / color / mirror / Atom feed
From: Gleb Natapov <gleb@redhat.com>
To: avi@redhat.com
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH 9/9] [SVM] inject NMI after IRET from a previous NMI, not before.
Date: Tue, 5 May 2009 12:47:35 +0300	[thread overview]
Message-ID: <20090505094735.GP9795@redhat.com> (raw)
In-Reply-To: <1241511275-2261-9-git-send-email-gleb@redhat.com>

I noticed a small bug in previous patch. Use this one instead.
(change update_db_intercept(to_svm(svm)) -> update_db_intercept(&svm->vcpu))


If NMI is received during handling of another NMI it should be injected
immediately after IRET from previous NMI handler, but SVM intercept IRET
before instruction execution so we can't inject pending NMI at this
point and there is not way to request exit when NMI window opens. This
patch fix SVM code to open NMI window after IRET by single stepping over
IRET instruction.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index fea0429..bcd0857 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -358,6 +358,7 @@ struct kvm_vcpu_arch {
 	unsigned int time_offset;
 	struct page *time_page;
 
+	bool singlestep; /* guest is single stepped by KVM */
 	bool nmi_pending;
 	bool nmi_injected;
 
@@ -772,6 +773,7 @@ enum {
 #define HF_HIF_MASK		(1 << 1)
 #define HF_VINTR_MASK		(1 << 2)
 #define HF_NMI_MASK		(1 << 3)
+#define HF_IRET_MASK		(1 << 4)
 
 /*
  * Hardware virtualization extension instructions may fault if a
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d5173a2..5c00258 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -933,15 +933,16 @@ static void svm_set_segment(struct kvm_vcpu *vcpu,
 
 }
 
-static int svm_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
+static void update_db_intercept(struct kvm_vcpu *vcpu)
 {
-	int old_debug = vcpu->guest_debug;
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	vcpu->guest_debug = dbg->control;
-
 	svm->vmcb->control.intercept_exceptions &=
 		~((1 << DB_VECTOR) | (1 << BP_VECTOR));
+
+	if (vcpu->arch.singlestep)
+		svm->vmcb->control.intercept_exceptions |= (1 << DB_VECTOR);
+
 	if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) {
 		if (vcpu->guest_debug &
 		    (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))
@@ -952,6 +953,16 @@ static int svm_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
 				1 << BP_VECTOR;
 	} else
 		vcpu->guest_debug = 0;
+}
+
+static int svm_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
+{
+	int old_debug = vcpu->guest_debug;
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	vcpu->guest_debug = dbg->control;
+
+	update_db_intercept(vcpu);
 
 	if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
 		svm->vmcb->save.dr7 = dbg->arch.debugreg[7];
@@ -1101,14 +1112,30 @@ static int pf_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
 static int db_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
 {
 	if (!(svm->vcpu.guest_debug &
-	      (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))) {
+	      (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)) &&
+		!svm->vcpu.arch.singlestep) {
 		kvm_queue_exception(&svm->vcpu, DB_VECTOR);
 		return 1;
 	}
-	kvm_run->exit_reason = KVM_EXIT_DEBUG;
-	kvm_run->debug.arch.pc = svm->vmcb->save.cs.base + svm->vmcb->save.rip;
-	kvm_run->debug.arch.exception = DB_VECTOR;
-	return 0;
+
+	if (svm->vcpu.arch.singlestep) {
+		svm->vcpu.arch.singlestep = false;
+		if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP))
+			svm->vmcb->save.rflags &=
+				~(X86_EFLAGS_TF | X86_EFLAGS_RF);
+		update_db_intercept(&svm->vcpu);
+	}
+
+	if (svm->vcpu.guest_debug &
+	    (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)){
+		kvm_run->exit_reason = KVM_EXIT_DEBUG;
+		kvm_run->debug.arch.pc =
+			svm->vmcb->save.cs.base + svm->vmcb->save.rip;
+		kvm_run->debug.arch.exception = DB_VECTOR;
+		return 0;
+	}
+
+	return 1;
 }
 
 static int bp_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
@@ -1855,7 +1882,7 @@ static int iret_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
 {
 	++svm->vcpu.stat.nmi_window_exits;
 	svm->vmcb->control.intercept &= ~(1UL << INTERCEPT_IRET);
-	svm->vcpu.arch.hflags &= ~HF_NMI_MASK;
+	svm->vcpu.arch.hflags |= HF_IRET_MASK;
 	return 1;
 }
 
@@ -2331,8 +2358,16 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	if (svm->vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK)
-		enable_irq_window(vcpu);
+	if ((svm->vcpu.arch.hflags & (HF_NMI_MASK | HF_IRET_MASK))
+	    == HF_NMI_MASK)
+		return; /* IRET will cause a vm exit */
+
+	/* Something prevents NMI from been injected. Single step over
+	   possible problem (IRET or exception injection or interrupt
+	   shadow) */
+	vcpu->arch.singlestep = true;
+	svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
+	update_db_intercept(vcpu);
 }
 
 static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr)
@@ -2375,6 +2410,9 @@ static void svm_complete_interrupts(struct vcpu_svm *svm)
 	int type;
 	u32 exitintinfo = svm->vmcb->control.exit_int_info;
 
+	if (svm->vcpu.arch.hflags & HF_IRET_MASK)
+		svm->vcpu.arch.hflags &= ~(HF_NMI_MASK | HF_IRET_MASK);
+
 	svm->vcpu.arch.nmi_injected = false;
 	kvm_clear_exception_queue(&svm->vcpu);
 	kvm_clear_interrupt_queue(&svm->vcpu);
--
			Gleb.

      parent reply	other threads:[~2009-05-05  9:47 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-05-05  8:14 [PATCH 1/9] Unprotect a page if #PF happens during NMI injection Gleb Natapov
2009-05-05  8:14 ` [PATCH 2/9] Do not allow interrupt injection from userspace if there is a pending event Gleb Natapov
2009-05-05  8:14 ` [PATCH 3/9] Remove irq_pending bitmap Gleb Natapov
2009-05-06  5:55   ` Sheng Yang
2009-05-06  6:50     ` Sheng Yang
2009-05-05  8:14 ` [PATCH 4/9] [SVM] skip_emulated_instruction() decode an instruction if size is not known Gleb Natapov
2009-05-05  8:14 ` [PATCH 5/9] [VMX] Do not re-execute INTn instruction Gleb Natapov
2009-05-06  6:57   ` Sheng Yang
2009-05-06  9:27     ` Gleb Natapov
2009-05-06  9:30       ` Avi Kivity
2009-05-06 10:59   ` Gregory Haskins
2009-05-06 11:46   ` Gleb Natapov
2009-05-05  8:14 ` [PATCH 6/9] IRQ/NMI window should always be requested Gleb Natapov
2009-05-05  8:14 ` [PATCH 7/9] Drop interrupt shadow when single stepping should be done only on VMX Gleb Natapov
2009-05-05  8:14 ` [PATCH 8/9] Replace pending exception by PF if it happens serially Gleb Natapov
2009-05-05  8:14 ` [PATCH 9/9] [SVM] inject NMI after IRET from a previous NMI, not before Gleb Natapov
2009-05-05  8:45   ` Jan Kiszka
2009-05-05  9:03     ` Gleb Natapov
2009-05-05  9:25       ` Jan Kiszka
2009-05-05  9:32         ` Gleb Natapov
2009-05-05  9:47   ` Gleb Natapov [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20090505094735.GP9795@redhat.com \
    --to=gleb@redhat.com \
    --cc=avi@redhat.com \
    --cc=kvm@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.