Skip to content

Commit

Permalink
KVM: x86: Fix guest debug across vcpu INIT reset
Browse files Browse the repository at this point in the history 
If we reset a vcpu on INIT, we so far overwrote dr7 as provided by
KVM_SET_GUEST_DEBUG, and we also cleared switch_db_regs unconditionally.

Fix this by saving the dr7 used for guest debugging and calculating the
effective register value as well as switch_db_regs on any potential
change. This will change to focus of the set_guest_debug vendor op to
update_dp_bp_intercept.

Found while trying to stop on start_secondary.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
  • Loading branch information
Jan Kiszka authored and Avi Kivity committed Sep 23, 2012
1 parent 7a84428 commit c863901
Show file tree
Hide file tree
Showing 4 changed files with 24 additions and 43 deletions.
4 changes: 2 additions & 2 deletions arch/x86/include/asm/kvm_host.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -471,6 +471,7 @@ struct kvm_vcpu_arch {
unsigned long dr6;
unsigned long dr7;
unsigned long eff_db[KVM_NR_DB_REGS];
unsigned long guest_debug_dr7;

u64 mcg_cap;
u64 mcg_status;
Expand Down Expand Up @@ -647,8 +648,7 @@ struct kvm_x86_ops {
void (*vcpu_load)(struct kvm_vcpu *vcpu, int cpu);
void (*vcpu_put)(struct kvm_vcpu *vcpu);

void (*set_guest_debug)(struct kvm_vcpu *vcpu,
struct kvm_guest_debug *dbg);
void (*update_db_bp_intercept)(struct kvm_vcpu *vcpu);
int (*get_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata);
int (*set_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
u64 (*get_segment_base)(struct kvm_vcpu *vcpu, int seg);
Expand Down
23 changes: 4 additions & 19 deletions arch/x86/kvm/svm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1146,7 +1146,6 @@ static void init_vmcb(struct vcpu_svm *svm)

svm_set_efer(&svm->vcpu, 0);
save->dr6 = 0xffff0ff0;
save->dr7 = 0x400;
kvm_set_rflags(&svm->vcpu, 2);
save->rip = 0x0000fff0;
svm->vcpu.arch.regs[VCPU_REGS_RIP] = save->rip;
Expand Down Expand Up @@ -1643,7 +1642,7 @@ static void svm_set_segment(struct kvm_vcpu *vcpu,
mark_dirty(svm->vmcb, VMCB_SEG);
}

static void update_db_intercept(struct kvm_vcpu *vcpu)
static void update_db_bp_intercept(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);

Expand All @@ -1663,20 +1662,6 @@ static void update_db_intercept(struct kvm_vcpu *vcpu)
vcpu->guest_debug = 0;
}

static void svm_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
{
struct vcpu_svm *svm = to_svm(vcpu);

if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
svm->vmcb->save.dr7 = dbg->arch.debugreg[7];
else
svm->vmcb->save.dr7 = vcpu->arch.dr7;

mark_dirty(svm->vmcb, VMCB_DR);

update_db_intercept(vcpu);
}

static void new_asid(struct vcpu_svm *svm, struct svm_cpu_data *sd)
{
if (sd->next_asid > sd->max_asid) {
Expand Down Expand Up @@ -1748,7 +1733,7 @@ static int db_interception(struct vcpu_svm *svm)
if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP))
svm->vmcb->save.rflags &=
~(X86_EFLAGS_TF | X86_EFLAGS_RF);
update_db_intercept(&svm->vcpu);
update_db_bp_intercept(&svm->vcpu);
}

if (svm->vcpu.guest_debug &
Expand Down Expand Up @@ -3659,7 +3644,7 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
*/
svm->nmi_singlestep = true;
svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
update_db_intercept(vcpu);
update_db_bp_intercept(vcpu);
}

static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr)
Expand Down Expand Up @@ -4253,7 +4238,7 @@ static struct kvm_x86_ops svm_x86_ops = {
.vcpu_load = svm_vcpu_load,
.vcpu_put = svm_vcpu_put,

.set_guest_debug = svm_guest_debug,
.update_db_bp_intercept = update_db_bp_intercept,
.get_msr = svm_get_msr,
.set_msr = svm_set_msr,
.get_segment_base = svm_get_segment_base,
Expand Down
14 changes: 1 addition & 13 deletions arch/x86/kvm/vmx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2288,16 +2288,6 @@ static void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
}
}

static void set_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
{
if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
vmcs_writel(GUEST_DR7, dbg->arch.debugreg[7]);
else
vmcs_writel(GUEST_DR7, vcpu->arch.dr7);

update_exception_bitmap(vcpu);
}

static __init int cpu_has_kvm_support(void)
{
return cpu_has_vmx();
Expand Down Expand Up @@ -3960,8 +3950,6 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
kvm_rip_write(vcpu, 0);
kvm_register_write(vcpu, VCPU_REGS_RSP, 0);

vmcs_writel(GUEST_DR7, 0x400);

vmcs_writel(GUEST_GDTR_BASE, 0);
vmcs_write32(GUEST_GDTR_LIMIT, 0xffff);

Expand Down Expand Up @@ -7237,7 +7225,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
.vcpu_load = vmx_vcpu_load,
.vcpu_put = vmx_vcpu_put,

.set_guest_debug = set_guest_debug,
.update_db_bp_intercept = update_exception_bitmap,
.get_msr = vmx_get_msr,
.set_msr = vmx_set_msr,
.get_segment_base = vmx_get_segment_base,
Expand Down
26 changes: 17 additions & 9 deletions arch/x86/kvm/x86.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -692,6 +692,18 @@ unsigned long kvm_get_cr8(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_get_cr8);

static void kvm_update_dr7(struct kvm_vcpu *vcpu)
{
unsigned long dr7;

if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
dr7 = vcpu->arch.guest_debug_dr7;
else
dr7 = vcpu->arch.dr7;
kvm_x86_ops->set_dr7(vcpu, dr7);
vcpu->arch.switch_db_regs = (dr7 & DR7_BP_EN_MASK);
}

static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
{
switch (dr) {
Expand All @@ -717,10 +729,7 @@ static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
if (val & 0xffffffff00000000ULL)
return -1; /* #GP */
vcpu->arch.dr7 = (val & DR7_VOLATILE) | DR7_FIXED_1;
if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)) {
kvm_x86_ops->set_dr7(vcpu, vcpu->arch.dr7);
vcpu->arch.switch_db_regs = (val & DR7_BP_EN_MASK);
}
kvm_update_dr7(vcpu);
break;
}

Expand Down Expand Up @@ -5851,13 +5860,12 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) {
for (i = 0; i < KVM_NR_DB_REGS; ++i)
vcpu->arch.eff_db[i] = dbg->arch.debugreg[i];
vcpu->arch.switch_db_regs =
(dbg->arch.debugreg[7] & DR7_BP_EN_MASK);
vcpu->arch.guest_debug_dr7 = dbg->arch.debugreg[7];
} else {
for (i = 0; i < KVM_NR_DB_REGS; i++)
vcpu->arch.eff_db[i] = vcpu->arch.db[i];
vcpu->arch.switch_db_regs = (vcpu->arch.dr7 & DR7_BP_EN_MASK);
}
kvm_update_dr7(vcpu);

if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
vcpu->arch.singlestep_rip = kvm_rip_read(vcpu) +
Expand All @@ -5869,7 +5877,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
*/
kvm_set_rflags(vcpu, rflags);

kvm_x86_ops->set_guest_debug(vcpu, dbg);
kvm_x86_ops->update_db_bp_intercept(vcpu);

r = 0;

Expand Down Expand Up @@ -6045,10 +6053,10 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
vcpu->arch.nmi_pending = 0;
vcpu->arch.nmi_injected = false;

vcpu->arch.switch_db_regs = 0;
memset(vcpu->arch.db, 0, sizeof(vcpu->arch.db));
vcpu->arch.dr6 = DR6_FIXED_1;
vcpu->arch.dr7 = DR7_FIXED_1;
kvm_update_dr7(vcpu);

kvm_make_request(KVM_REQ_EVENT, vcpu);
vcpu->arch.apf.msr_val = 0;
Expand Down

0 comments on commit c863901

Please sign in to comment.