KVM: x86: Fix DR7 mask on task-switch while debugging (3db176d5) · Commits · 戴 / test

If the host sets hardware breakpoints to debug the guest, and a task-switch occurs in the guest, the architectural DR7 will not be updated. The effective DR7 would be updated instead. This fix puts the DR7 update during task-switch emulation, so it now uses the standard DR setting mechanism instead of the one that was previously used. As a bonus, the update of DR7 will now be effective for AMD as well. Signed-off-by:

Nadav Amit <namit@cs.technion.ac.il> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/emulate.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -25,6 +25,7 @@
		#include <linux/module.h>
		#include <asm/kvm_emulate.h>
		#include <linux/stringify.h>
		#include <asm/debugreg.h>

		#include "x86.h"
		#include "tss.h"
		@@ -2849,7 +2850,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
		ulong old_tss_base =
		ops->get_cached_segment_base(ctxt, VCPU_SREG_TR);
		u32 desc_limit;
		ulong desc_addr;
		ulong desc_addr, dr7;

		/* FIXME: old_tss_base == ~0 ? */

		@@ -2934,6 +2935,9 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
		ret = em_push(ctxt);
		}

		ops->get_dr(ctxt, 7, &dr7);
		ops->set_dr(ctxt, 7, dr7 & ~(DR_LOCAL_ENABLE_MASK \| DR_LOCAL_SLOWDOWN));

		return ret;
		}

arch/x86/kvm/vmx.c

+0 −3

Original line number	Diff line number	Diff line
		@@ -5708,9 +5708,6 @@ static int handle_task_switch(struct kvm_vcpu *vcpu)
		return 0;
		}

		/* clear all local breakpoint enable flags */
		vmcs_writel(GUEST_DR7, vmcs_readl(GUEST_DR7) & ~0x155);

		/*
		* TODO: What about debug traps on tss switch?
		* Are we supposed to inject them and update dr6?

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