On Tuesday 11 November 2014 08:54 AM, David Gibson wrote:
[..]
So, this may not still be possible depending on whether the KVM side
of this is already merged, but it occurs to me that there's a simpler
way.
Rather than mucking about with having to update the hypervisor on the
RTAS location, they have qemu copy the code out of RTAS, patch it and
copy it back into the vector, you could instead do this:
1. Make KVM instead of immediately delivering a 0x200 for a guest
machine check, cause a special exit to qemu.
2. Have the register-nmi RTAS call store the guest side MC handler
address in the spapr structure, but perform no actual guest code
patching.
3. Allocate the error log buffer independently from the RTAS blob,
so qemu always knows where it is.
4. When qemu gets the MC exit condition, instead of going via a
patched 0x200 vector, just directly set the guest register state and
jump straight into the guest side MC handler.
Before I proceed further I would like to know what others think about
the approach proposed above (except for step 3 - as per PAPR the error
log buffer should be part of RTAS blob and hence we cannot have error
log buffer independent of RTAS blob).
Alex, Alexey, Ben: Any thoughts?