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KVM: MMU: Track page fault data in struct vcpu
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This patch introduces a struct with two new fields in
vcpu_arch for x86:

	* fault.address
	* fault.error_code

This will be used to correctly propagate page faults back
into the guest when we could have either an ordinary page
fault or a nested page fault. In the case of a nested page
fault the fault-address is different from the original
address that should be walked. So we need to keep track
about the real fault-address.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
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Joerg Roedel authored and Avi Kivity committed Oct 24, 2010
1 parent 3241f22 commit 8df25a3
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Showing 6 changed files with 38 additions and 31 deletions.
1 change: 0 additions & 1 deletion arch/x86/include/asm/kvm_emulate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -229,7 +229,6 @@ struct x86_emulate_ctxt {
int exception; /* exception that happens during emulation or -1 */
u32 error_code; /* error code for exception */
bool error_code_valid;
unsigned long cr2; /* faulted address in case of #PF */

/* decode cache */
struct decode_cache decode;
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17 changes: 12 additions & 5 deletions arch/x86/include/asm/kvm_host.h
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Original file line number Diff line number Diff line change
Expand Up @@ -239,9 +239,7 @@ struct kvm_mmu {
void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long root);
unsigned long (*get_cr3)(struct kvm_vcpu *vcpu);
int (*page_fault)(struct kvm_vcpu *vcpu, gva_t gva, u32 err);
void (*inject_page_fault)(struct kvm_vcpu *vcpu,
unsigned long addr,
u32 error_code);
void (*inject_page_fault)(struct kvm_vcpu *vcpu);
void (*free)(struct kvm_vcpu *vcpu);
gpa_t (*gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t gva, u32 access,
u32 *error);
Expand Down Expand Up @@ -288,6 +286,16 @@ struct kvm_vcpu_arch {
bool tpr_access_reporting;

struct kvm_mmu mmu;

/*
* This struct is filled with the necessary information to propagate a
* page fault into the guest
*/
struct {
u64 address;
unsigned error_code;
} fault;

/* only needed in kvm_pv_mmu_op() path, but it's hot so
* put it here to avoid allocation */
struct kvm_pv_mmu_op_buffer mmu_op_buffer;
Expand Down Expand Up @@ -624,8 +632,7 @@ void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr);
void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);
void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr);
void kvm_requeue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);
void kvm_inject_page_fault(struct kvm_vcpu *vcpu, unsigned long cr2,
u32 error_code);
void kvm_inject_page_fault(struct kvm_vcpu *vcpu);
bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);

int kvm_pic_set_irq(void *opaque, int irq, int level);
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30 changes: 14 additions & 16 deletions arch/x86/kvm/emulate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -487,11 +487,9 @@ static void emulate_gp(struct x86_emulate_ctxt *ctxt, int err)
emulate_exception(ctxt, GP_VECTOR, err, true);
}

static void emulate_pf(struct x86_emulate_ctxt *ctxt, unsigned long addr,
int err)
static void emulate_pf(struct x86_emulate_ctxt *ctxt)
{
ctxt->cr2 = addr;
emulate_exception(ctxt, PF_VECTOR, err, true);
emulate_exception(ctxt, PF_VECTOR, 0, true);
}

static void emulate_ud(struct x86_emulate_ctxt *ctxt)
Expand Down Expand Up @@ -834,7 +832,7 @@ static int read_emulated(struct x86_emulate_ctxt *ctxt,
rc = ops->read_emulated(addr, mc->data + mc->end, n, &err,
ctxt->vcpu);
if (rc == X86EMUL_PROPAGATE_FAULT)
emulate_pf(ctxt, addr, err);
emulate_pf(ctxt);
if (rc != X86EMUL_CONTINUE)
return rc;
mc->end += n;
Expand Down Expand Up @@ -921,7 +919,7 @@ static int read_segment_descriptor(struct x86_emulate_ctxt *ctxt,
addr = dt.address + index * 8;
ret = ops->read_std(addr, desc, sizeof *desc, ctxt->vcpu, &err);
if (ret == X86EMUL_PROPAGATE_FAULT)
emulate_pf(ctxt, addr, err);
emulate_pf(ctxt);

return ret;
}
Expand All @@ -947,7 +945,7 @@ static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
addr = dt.address + index * 8;
ret = ops->write_std(addr, desc, sizeof *desc, ctxt->vcpu, &err);
if (ret == X86EMUL_PROPAGATE_FAULT)
emulate_pf(ctxt, addr, err);
emulate_pf(ctxt);

return ret;
}
Expand Down Expand Up @@ -1117,7 +1115,7 @@ static inline int writeback(struct x86_emulate_ctxt *ctxt,
&err,
ctxt->vcpu);
if (rc == X86EMUL_PROPAGATE_FAULT)
emulate_pf(ctxt, c->dst.addr.mem, err);
emulate_pf(ctxt);
if (rc != X86EMUL_CONTINUE)
return rc;
break;
Expand Down Expand Up @@ -1939,7 +1937,7 @@ static int task_switch_16(struct x86_emulate_ctxt *ctxt,
&err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, old_tss_base, err);
emulate_pf(ctxt);
return ret;
}

Expand All @@ -1949,15 +1947,15 @@ static int task_switch_16(struct x86_emulate_ctxt *ctxt,
&err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, old_tss_base, err);
emulate_pf(ctxt);
return ret;
}

ret = ops->read_std(new_tss_base, &tss_seg, sizeof tss_seg, ctxt->vcpu,
&err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, new_tss_base, err);
emulate_pf(ctxt);
return ret;
}

Expand All @@ -1970,7 +1968,7 @@ static int task_switch_16(struct x86_emulate_ctxt *ctxt,
ctxt->vcpu, &err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, new_tss_base, err);
emulate_pf(ctxt);
return ret;
}
}
Expand Down Expand Up @@ -2081,7 +2079,7 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
&err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, old_tss_base, err);
emulate_pf(ctxt);
return ret;
}

Expand All @@ -2091,15 +2089,15 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
&err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, old_tss_base, err);
emulate_pf(ctxt);
return ret;
}

ret = ops->read_std(new_tss_base, &tss_seg, sizeof tss_seg, ctxt->vcpu,
&err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, new_tss_base, err);
emulate_pf(ctxt);
return ret;
}

Expand All @@ -2112,7 +2110,7 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
ctxt->vcpu, &err);
if (ret == X86EMUL_PROPAGATE_FAULT) {
/* FIXME: need to provide precise fault address */
emulate_pf(ctxt, new_tss_base, err);
emulate_pf(ctxt);
return ret;
}
}
Expand Down
6 changes: 2 additions & 4 deletions arch/x86/kvm/mmu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2566,11 +2566,9 @@ static unsigned long get_cr3(struct kvm_vcpu *vcpu)
return vcpu->arch.cr3;
}

static void inject_page_fault(struct kvm_vcpu *vcpu,
u64 addr,
u32 err_code)
static void inject_page_fault(struct kvm_vcpu *vcpu)
{
vcpu->arch.mmu.inject_page_fault(vcpu, addr, err_code);
vcpu->arch.mmu.inject_page_fault(vcpu);
}

static void paging_free(struct kvm_vcpu *vcpu)
Expand Down
6 changes: 5 additions & 1 deletion arch/x86/kvm/paging_tmpl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -258,6 +258,10 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
walker->error_code |= PFERR_FETCH_MASK;
if (rsvd_fault)
walker->error_code |= PFERR_RSVD_MASK;

vcpu->arch.fault.address = addr;
vcpu->arch.fault.error_code = walker->error_code;

trace_kvm_mmu_walker_error(walker->error_code);
return 0;
}
Expand Down Expand Up @@ -521,7 +525,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
*/
if (!r) {
pgprintk("%s: guest page fault\n", __func__);
inject_page_fault(vcpu, addr, walker.error_code);
inject_page_fault(vcpu);
vcpu->arch.last_pt_write_count = 0; /* reset fork detector */
return 0;
}
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9 changes: 5 additions & 4 deletions arch/x86/kvm/x86.c
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Original file line number Diff line number Diff line change
Expand Up @@ -329,11 +329,12 @@ void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned nr)
}
EXPORT_SYMBOL_GPL(kvm_requeue_exception);

void kvm_inject_page_fault(struct kvm_vcpu *vcpu, unsigned long addr,
u32 error_code)
void kvm_inject_page_fault(struct kvm_vcpu *vcpu)
{
unsigned error_code = vcpu->arch.fault.error_code;

++vcpu->stat.pf_guest;
vcpu->arch.cr2 = addr;
vcpu->arch.cr2 = vcpu->arch.fault.address;
kvm_queue_exception_e(vcpu, PF_VECTOR, error_code);
}

Expand Down Expand Up @@ -4080,7 +4081,7 @@ static void inject_emulated_exception(struct kvm_vcpu *vcpu)
{
struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
if (ctxt->exception == PF_VECTOR)
kvm_inject_page_fault(vcpu, ctxt->cr2, ctxt->error_code);
kvm_inject_page_fault(vcpu);
else if (ctxt->error_code_valid)
kvm_queue_exception_e(vcpu, ctxt->exception, ctxt->error_code);
else
Expand Down

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