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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: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2015-04-19 21:12:59 +03:00 committed by Paolo Bonzini
parent cba3d2765e
commit 3db176d5b4
2 changed files with 5 additions and 4 deletions
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6
arch/x86/kvm/emulate.c
View File

@ -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;
}

3
arch/x86/kvm/vmx.c
View File

@ -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?