Re: [Xen-devel] Nested events in 64bit mini-OS

[Xu Zhang <xzhang@xxxxxxxxxx>]

Dear all,

I haven't seen any updates on this matter, so I try to come up with a 
fix. Generally speaking, I want to mimic 32-bit mini-OS behaviour, adding:
1) a fixup table: for each byte offset in the critical region, it 
provides the number of bytes which have already been popped from the 
interrupted stack frame.
2) a fixup routine: obtain number of restored registers by quickly 
looking up the fixup table and coalesce the current stack frame with the 
just-interrupted one.
3) checks against re-entrance in hypervisor_callback

The "git diff" output is attached to this email. I only did some naive 
"tests" by running it inside gdb. I am wondering is there a test suite 
for mini-OS? A follow-up question is that given this fix, do you still 
need hypercall iret?
Thank you very much.

Regards,
Xu Zhang

On 10/25/2012 03:56 PM, Samuel Thibault wrote:
> Xu Zhang, le Tue 23 Oct 2012 17:43:28 -0500, a écrit :
> > 64-bit mini-OS seems to adopt a mixed use of both (in HYPERVISOR_IRET).
> > mini-OS doesn't have an userspace, so unless an NMI happened, it always
> > perform interrupt/exception return with machine instruction iret, without
> > checking against nested events. This is wrong to me. Am I missing something
> > here?
> I don't think you are missing anything. Cc-ing Grzegorz, who actually
> wrote the code.
>
> Samuel

Attachment: fixup.diff
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