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Re: [Xen-devel] [RFC PATCH 00/84] Remove direct map from Xen



Hi,

On 9/26/19 11:33 AM, hongyax@xxxxxxxxxx wrote:
On 26/09/2019 11:21, Julien Grall wrote:
Hi,

Thank you for posting the series.

On 9/26/19 10:45 AM, hongyax@xxxxxxxxxx wrote:
From: Hongyan Xia <hongyax@xxxxxxxxxx>

Previously, Wei Liu has created the patch series to switch to
alloc/map/unmap/free APIs for Xen page tables so that Xen page tables
are mapped with map_domain_page(). This is the first step towards
removing the direct map. I implemented patches on top of Wei's to remove
the direct map completely.

In addition to Wei's, my patches:
- (Wei) implement a proper PMAP infrastructure for bootstrapping
- remove direct map code in map_domain_page() and use mapcache, use PMAP
  when mapcache not ready
- map/unmap xenheap allocations to the direct map region so that va<->pa
  macros still work
- install dummy mappings (no permissions, INVALID_MFN) instead of actual
  1:1 mappings during boot, so the direct map no longer exists
- fix many places where code incorrectly assumes a direct map

I am a bit confused. Are your patches fixing bug from Wei's series?


The goal is to remove the direct map completely from Xen. Wei's series has done the first step but was not complete. My additional patches finished the remaining steps and removed the direct map.

So I understand this correctly, Wei's series has no bug in it and could be committed as is without breaking Xen. Am I correct?

The reason I am asking that if you have a few patches that say fix leak/bug. If they are bug in Wei's series, then they should be squashed in patches introducing them.



I have moderately tested the patches. I am able to boot into dom0,
create/destroy PV/HVM guests and run XTF tests. Personally, I find it
difficult to discover all places where it incorrectly assumes a direct
map, so reviews and further testing are more than welcome.

Do you have a branch with this series applied?


I am setting this up. Will send out the link to the branch soon.

Thank you.

Cheers,

--
Julien Grall

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