Marcelo Tosatti wrote:
On Wed, Feb 10, 2010 at 06:25:42PM +0200, Avi Kivity wrote:
On 02/10/2010 03:50 AM, Takuya Yoshikawa wrote:
This patch injects page fault when reading descriptor in
load_guest_segment_descriptor() fails with FAULT.
Effects of this injection: This function is used by
kvm_load_segment_descriptor() which is necessary for the
following instructions.
- mov seg,r/m16
- jmp far
- pop ?s
This patch makes it possible to emulate the page faults
generated by these instructions. But be sure that unless
we change the kvm_load_segment_descriptor()'s ret value
propagation this patch has no effect.
@@ -4655,6 +4655,7 @@ static int load_guest_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
{
struct descriptor_table dtable;
u16 index = selector>> 3;
+ int ret;
get_segment_descriptor_dtable(vcpu, selector,&dtable);
@@ -4662,7 +4663,11 @@ static int load_guest_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
kvm_queue_exception_e(vcpu, GP_VECTOR, selector& 0xfffc);
return X86EMUL_PROPAGATE_FAULT;
}
- return kvm_read_guest_virt(dtable.base + index*8, seg_desc, sizeof(*seg_desc), vcpu);
+ ret = kvm_read_guest_virt(dtable.base + index*8, seg_desc, sizeof(*seg_desc), vcpu);
+ if (ret == X86EMUL_PROPAGATE_FAULT)
+ kvm_inject_page_fault(vcpu, dtable.base + index*8, 0);
+
+ return ret;
}
If the descriptor table is not aligned, and a descriptor spans two
pages, then we might need to inject a page fault at some other
address.
Also, the injection should be done in kvm_read_guest_virt() to avoid
duplicating code.
These instructions however are only emulated in big real mode.
Where did you encounter the need to inject page faults during their
emulation?
Task switch exits also use them, so it should inject faults as
documented.
Yes, though I did not touch the task switch parts, we will have to do.
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