[Xen-ia64-devel] [patch 0/7] Kexec: EFI Mapping: Take III

[Simon Horman <horms@xxxxxxxxxxxx>]

Hi,

here is an update on the patch series to solve the EFI mapping for kexec.
The major change is to remove the C-code portions of the page fault
handling changes and instead implement all of the identity mapping
in assembly, as suggested by Tristan Gingold.

Although this does make the assembly a little bulkier, removing the
aditional complexity from the C code does seem to be a win, and I beleive
that overall there are less lines of code changed (though I haven't
counted).

For the sake of completeness, the description posted with
the original series is below.

--
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/

This series is my latest attempt to solve the EFI mapping problem for
Kexec. In short the problem is that the mapping can only be made once,
which presents a problem when kexecing (or kdumping) between Xen and Linux
which place the EFI at different virtual addresses.

Put simply this series resolves this problem by having Xen map EFI into the
same place as Linux. The problem and this solution are discussed in more
detail in the comment attached to the third patch in the series.

The first four patches in this series were previously posted along with the
rest of the kexec patches. Kexec has been merged, however these patches
were left out because of some concerns:

1. VMX domains should not be able to access the EFI memory directly

2. Domains should be able to use the virtual addresses that are
   now used for EFI, as these virtual addresses are in the space used
   by domains, not the space usually used by Xen.

To resolve this problem the fifth pach has been added to the series.  As
suggested by Yamahata-san, this patch uses a special RID for EFI memory
accesses, thus allowing the page handler to restrict access to Xen, which
should resolve both of the problems above. This is discussed in a little


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