On Mon, 07 Apr 2008 11:05:06 -0500
Anthony Liguori <[EMAIL PROTECTED]> wrote:
> Perhaps a viable way to fix this upstream would be to catch the vmentry
> failure, look to see if SS.CPL != CS.CPL, and if so, invoke
> x86_emulate() in a loop until SS.CPL == CS.CPL.
>
> There are very few instructions in gfxboot that would need to be added
> to x86_emulate (if they aren't already there).
So to see if I'm on the good way here is an attempt to implement the
solution. It doesn't work yet.
I'm trying to:
- Disable the code that modifies SS value in order to detect VM entry
failure
- Add the handler that catches the VM entry failure
- Emulate the instruction until we recover a friendly VMX state
=> add the jmp far (opcode 0xea) instruction in the emulation.
With the patch, the VM entry failure is caught but the jmp far
instruction seems to fail. I've got the following dmesg:
...
handle_vmentry_failure: invalid guest state
handle_vmentry_failure: start emulation
handle_vmentry_failure: emulation failed
...
Regards,
Guillaume
---
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 8e5d664..a56bd83 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1178,13 +1178,16 @@ static void enter_pmode(struct kvm_vcpu *vcpu)
update_exception_bitmap(vcpu);
+ fix_pmode_dataseg(VCPU_SREG_SS, &vcpu->arch.rmode.ss);
fix_pmode_dataseg(VCPU_SREG_ES, &vcpu->arch.rmode.es);
fix_pmode_dataseg(VCPU_SREG_DS, &vcpu->arch.rmode.ds);
fix_pmode_dataseg(VCPU_SREG_GS, &vcpu->arch.rmode.gs);
fix_pmode_dataseg(VCPU_SREG_FS, &vcpu->arch.rmode.fs);
+#if 0
vmcs_write16(GUEST_SS_SELECTOR, 0);
vmcs_write32(GUEST_SS_AR_BYTES, 0x93);
+#endif
vmcs_write16(GUEST_CS_SELECTOR,
vmcs_read16(GUEST_CS_SELECTOR) & ~SELECTOR_RPL_MASK);
@@ -1952,6 +1955,33 @@ static int handle_rmode_exception(struct kvm_vcpu *vcpu,
return 0;
}
+static int handle_vmentry_failure(u32 exit_reason, struct kvm_vcpu *vcpu)
+{
+ unsigned int basic_exit_reason = (uint16_t) exit_reason;
+ unsigned int cs_rpl = vmcs_read16(GUEST_CS_SELECTOR) &
SELECTOR_RPL_MASK;
+ unsigned int ss_rpl = vmcs_read16(GUEST_SS_SELECTOR) &
SELECTOR_RPL_MASK;
+
+ switch (basic_exit_reason) {
+ case EXIT_REASON_INVALID_GUEST_STATE:
+ printk(KERN_INFO "%s: invalid guest state\n",
__FUNCTION__);
+ printk(KERN_INFO "%s: start emulation \n",
__FUNCTION__);
+ while (cs_rpl != ss_rpl) {
+ if (emulate_instruction(vcpu, NULL, 0, 0, 0) ==
EMULATE_FAIL) {
+ printk(KERN_INFO "%s: emulation
failed\n", __FUNCTION__);
+ return 0;
+ }
+ cs_rpl = vmcs_read16(GUEST_CS_SELECTOR) &
SELECTOR_RPL_MASK;
+ ss_rpl = vmcs_read16(GUEST_SS_SELECTOR) &
SELECTOR_RPL_MASK;
+ }
+ printk(KERN_INFO "%s: VMX friendly state recovered\n",
__FUNCTION__);
+ break;
+ default:
+ printk(KERN_INFO "VM-entry failure due to unkown
reason\n");
+ return 0;
+ }
+ return 1;
+}
+
static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -2364,6 +2394,9 @@ static int kvm_handle_exit(struct kvm_run *kvm_run,
struct kvm_vcpu *vcpu)
KVMTRACE_3D(VMEXIT, vcpu, exit_reason, (u32)vmcs_readl(GUEST_RIP),
(u32)((u64)vmcs_readl(GUEST_RIP) >> 32), entryexit);
+ if (unlikely(exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
+ return handle_vmentry_failure(exit_reason, vcpu);
+
if (unlikely(vmx->fail)) {
kvm_run->exit_reason = KVM_EXIT_FAIL_ENTRY;
kvm_run->fail_entry.hardware_entry_failure_reason
diff --git a/arch/x86/kvm/vmx.h b/arch/x86/kvm/vmx.h
index 5dff460..200c0f8 100644
--- a/arch/x86/kvm/vmx.h
+++ b/arch/x86/kvm/vmx.h
@@ -223,7 +223,10 @@ enum vmcs_field {
#define EXIT_REASON_IO_INSTRUCTION 30
#define EXIT_REASON_MSR_READ 31
#define EXIT_REASON_MSR_WRITE 32
+#define EXIT_REASON_INVALID_GUEST_STATE 33
+#define EXIT_REASON_MSR_LOADING 34
#define EXIT_REASON_MWAIT_INSTRUCTION 36
+#define EXIT_REASON_MACHINE_CHECK 41
#define EXIT_REASON_TPR_BELOW_THRESHOLD 43
#define EXIT_REASON_APIC_ACCESS 44
#define EXIT_REASON_WBINVD 54
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0ce5563..b38065d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3267,7 +3267,7 @@ static int load_segment_descriptor_to_kvm_desct(struct
kvm_vcpu *vcpu,
return 0;
}
-static int load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
+int load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
int type_bits, int seg)
{
struct kvm_segment kvm_seg;
diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 2ca0838..4bc3c80 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -168,7 +168,7 @@ static u16 opcode_table[256] = {
/* 0xE0 - 0xE7 */
0, 0, 0, 0, 0, 0, 0, 0,
/* 0xE8 - 0xEF */
- ImplicitOps | Stack, SrcImm|ImplicitOps, 0, SrcImmByte|ImplicitOps,
+ ImplicitOps | Stack, SrcImm|ImplicitOps, ImplicitOps,
SrcImmByte|ImplicitOps,
0, 0, 0, 0,
/* 0xF0 - 0xF7 */
0, 0, 0, 0,
@@ -1156,6 +1156,9 @@ static inline int emulate_grp45(struct x86_emulate_ctxt
*ctxt,
case 4: /* jmp abs */
c->eip = c->src.val;
break;
+ case 5: /* jmp far */
+ printk(KERN_INFO "Jmp far need to be implemented\n");
+ break;
case 6: /* push */
emulate_push(ctxt);
break;
@@ -1657,6 +1660,24 @@ special_insn:
break;
}
case 0xe9: /* jmp rel */
+ jmp_rel(c, c->src.val);
+ c->dst.type = OP_NONE; /* Disable writeback. */
+ break;
+ case 0xea: /* jmp far */ {
+ struct kvm_segment kvm_seg;
+ int ret;
+
+ kvm_x86_ops->get_segment(ctxt->vcpu, &kvm_seg, VCPU_SREG_CS);
+
+
+ ret = load_segment_descriptor(ctxt->vcpu, kvm_seg.selector, 9,
VCPU_SREG_CS);
+ if (ret < 0){
+ printk(KERN_INFO "%s: Failed to load CS descriptor\n",
__FUNCTION__);
+ return ret;
+ }
+
+ break;
+ }
case 0xeb: /* jmp rel short */
jmp_rel(c, c->src.val);
c->dst.type = OP_NONE; /* Disable writeback. */
diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h
index 31aa7d6..cdb5572 100644
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -270,7 +270,7 @@ struct kvm_vcpu_arch {
unsigned long base;
u32 limit;
u32 ar;
- } tr, es, ds, fs, gs;
+ } tr, es, ds, fs, gs, ss;
} rmode;
int halt_request; /* real mode on Intel only */
@@ -487,6 +487,8 @@ int emulator_get_dr(struct x86_emulate_ctxt *ctxt, int dr,
int emulator_set_dr(struct x86_emulate_ctxt *ctxt, int dr,
unsigned long value);
+int load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
+ int type_bits, int seg);
int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason);
void kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
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