On 06/09/18 16:29, Andrew Cooper wrote:
On 06/09/18 10:16, Paul Durrant wrote:
-----Original Message-----
From: Andrew Cooper [mailto:[email protected]]
Sent: 05 September 2018 19:12
To: Xen-devel <[email protected]>
Cc: Andrew Cooper <[email protected]>; Jan Beulich
<[email protected]>; Wei Liu <[email protected]>; Roger Pau Monne
<[email protected]>; Paul Durrant <[email protected]>; Stefano
Stabellini <[email protected]>; Julien Grall <[email protected]>
Subject: [PATCH 3/5] x86/hvm: Make
HVM_PARAM_{STORE,CONSOLE}_EVTCHN read-only to the guest
These values are set by the toolstack for each create/restore operation, and
bound by xen{store,console}d before the the guest starts running.
A guest has no reason to modify them at all, and the matching *_PFN
parameters
are already read-only. Adjust the *_EVTCHN permissions to be consistent.
Unfortunately this patch will break the Windows PV driver function here:
http://xenbits.xen.org/gitweb/?p=pvdrivers/win/xenbus.git;a=blob;f=src/xenbus/evtchn.c;hb=HEAD#l1037
Unfortunately the values really do change across a reset. It would be possible
to use volatile (disappear on reboot) registry keys to store the updated values
instead but I don't really see any harm in allowing the guest to update the
values to be correct, unless we want to change Xen to do the job so the guest
doesn't have to go through this dance.
:( Everything is terrible.
This is a general problem, not x86 specific, so I'll drop this patch and
make a similar adjustment to the ARM one.
I am a bit confused. I would have thought this was updated by the
toolstack at reset. So why would the guest update them?
Cheers,
--
Julien Grall
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