Am 15.08.22 um 12:09 schrieb Dmitry Osipenko:
On 8/15/22 13:05, Christian König wrote:
Am 15.08.22 um 11:54 schrieb Dmitry Osipenko:
Higher order pages allocated using alloc_pages() aren't refcounted and
they
need to be refcounted, otherwise it's impossible to map them by KVM. This
patch sets the refcount of the tail pages and fixes the KVM memory
mapping
faults.
Without this change guest virgl driver can't map host buffers into guest
and can't provide OpenGL 4.5 profile support to the guest. The host
mappings are also needed for enabling the Venus driver using host GPU
drivers that are utilizing TTM.
Based on a patch proposed by Trigger Huang.
Well I can't count how often I have repeated this: This is an absolutely
clear NAK!
TTM pages are not reference counted in the first place and because of
this giving them to virgl is illegal.
A? The first page is refcounted when allocated, the tail pages are not.
No they aren't. The first page is just by coincident initialized with a
refcount of 1. This refcount is completely ignored and not used at all.
Incrementing the reference count and by this mapping the page into some
other address space is illegal and corrupts the internal state tracking
of TTM.
Please immediately stop this completely broken approach. We have
discussed this multiple times now.
Could you please give me a link to these discussions?
Not of hand, please search the dri-devel list for similar patches. This
was brought up multiple times now.
Regards,
Christian.
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