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Commit 3db176d5 authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
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KVM: x86: Fix DR7 mask on task-switch while debugging 



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: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent cba3d276

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?