Avi Kivity wrote:
> Jan Kiszka wrote:
...
>> @@ -2234,6 +2252,24 @@ static int handle_rmode_exception(struct
>> if (((vec == GP_VECTOR) || (vec == SS_VECTOR)) && err_code == 0)
>> if (emulate_instruction(vcpu, NULL, 0, 0, 0) == EMULATE_DONE)
>> return 1;
>> + /*
>> + * Forward all other exceptions that are valid in real mode.
>> + * FIXME: Breaks guest debugging in real mode, need to be fixed with
>> + * the required debugging infrastructure rework.
>> + */
>> + switch (vec) {
>> + case DF_VECTOR:
>> + case SS_VECTOR:
>> + case GP_VECTOR:
>> + kvm_queue_exception_e(vcpu, vec, err_code);
>>
>
> These don't actually queue an error code in real mode. Compare the
> 'Real-Address Mode Exceptions' section with the 'Protected Mode
> Exceptions' section for most instructions in the Intel manual.
Unless you can points out a better reference, I prefer following chapter
5.15 of the System Programming Guide on this. And that one doesn't make
a difference when it says, e.g., "Exception Error Code: Zero. The
processor always pushes an error code of 0 onto the stack of the
doublefault handler."
>
>> + return 1;
>> + break;
>> + case DE_VECTOR ... NM_VECTOR:
>>
>
> Please spell out explicitly. Also, NM_VECTOR is used by the host for
> managing the guest fpu, so some NM_VECTORs should not be reflected. I
> suggest simply dropping NM_VECTOR until this is worked out, as many
> real-mode operating systems don't implement lazy fpu switching.
OK.
>
> Also, NMI shouldn't be handled here.
Yep.
>
>> + case MF_VECTOR:
>> + case MC_VECTOR:
>>
>
> I don't think #MC should be handled here. Machine checks have to be
> handled by the host.
OK, update below.
-------------
As we execute real mode guests in VM86 mode, exception have to be
reinjected appropriately when the guest triggered them. For this purpose
the patch adopts the real-mode injection pattern used in vmx_inject_irq
to vmx_queue_exception, additionally taking care that the IP is set
correctly for #BP exceptions. Furthermore it extends
handle_rmode_exception to reinject all those exceptions that can be
raised in real mode.
This fixes the execution of himem.exe from FreeDOS and also makes its
debug.com work properly.
Note that guest debugging in real mode is broken now. This has to be
fixed by the scheduled debugging infrastructure rework (will be done
once base patches for QEMU have been accepted).
Signed-off-by: Jan Kiszka <[EMAIL PROTECTED]>
---
arch/x86/kvm/vmx.c | 43 +++++++++++++++++++++++++++++++++++++++++--
include/asm-x86/kvm_host.h | 4 ++++
2 files changed, 45 insertions(+), 2 deletions(-)
Index: b/arch/x86/kvm/vmx.c
===================================================================
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -735,12 +735,30 @@ static void skip_emulated_instruction(st
static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
bool has_error_code, u32 error_code)
{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+ if (has_error_code)
+ vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE, error_code);
+
+ if (vcpu->arch.rmode.active) {
+ vmx->rmode.irq.pending = true;
+ vmx->rmode.irq.vector = nr;
+ vmx->rmode.irq.rip = kvm_rip_read(vcpu);
+ if (nr == BP_VECTOR)
+ vmx->rmode.irq.rip++;
+ vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
+ nr | INTR_TYPE_SOFT_INTR
+ | (has_error_code ? INTR_INFO_DELIVER_CODE_MASK :
0)
+ | INTR_INFO_VALID_MASK);
+ vmcs_write32(VM_ENTRY_INSTRUCTION_LEN, 1);
+ kvm_rip_write(vcpu, vmx->rmode.irq.rip - 1);
+ return;
+ }
+
vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
nr | INTR_TYPE_EXCEPTION
| (has_error_code ? INTR_INFO_DELIVER_CODE_MASK : 0)
| INTR_INFO_VALID_MASK);
- if (has_error_code)
- vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE, error_code);
}
static bool vmx_exception_injected(struct kvm_vcpu *vcpu)
@@ -2234,6 +2252,27 @@ static int handle_rmode_exception(struct
if (((vec == GP_VECTOR) || (vec == SS_VECTOR)) && err_code == 0)
if (emulate_instruction(vcpu, NULL, 0, 0, 0) == EMULATE_DONE)
return 1;
+ /*
+ * Forward all other exceptions that are valid in real mode.
+ * FIXME: Breaks guest debugging in real mode, need to be fixed with
+ * the required debugging infrastructure rework.
+ */
+ switch (vec) {
+ case DF_VECTOR:
+ case SS_VECTOR:
+ case GP_VECTOR:
+ kvm_queue_exception_e(vcpu, vec, err_code);
+ return 1;
+ case DE_VECTOR:
+ case DB_VECTOR:
+ case BP_VECTOR:
+ case OF_VECTOR:
+ case BR_VECTOR:
+ case UD_VECTOR:
+ case MF_VECTOR:
+ kvm_queue_exception(vcpu, vec);
+ return 1;
+ }
return 0;
}
Index: b/include/asm-x86/kvm_host.h
===================================================================
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -57,6 +57,9 @@
#define DE_VECTOR 0
#define DB_VECTOR 1
+#define BP_VECTOR 3
+#define OF_VECTOR 4
+#define BR_VECTOR 5
#define UD_VECTOR 6
#define NM_VECTOR 7
#define DF_VECTOR 8
@@ -65,6 +68,7 @@
#define SS_VECTOR 12
#define GP_VECTOR 13
#define PF_VECTOR 14
+#define MF_VECTOR 16
#define MC_VECTOR 18
#define SELECTOR_TI_MASK (1 << 2)
--
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