On 13/07/2018 16:03, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2018-07-13 15:51:50)
On 13/07/2018 11:59, Chris Wilson wrote:
+ /* Now enforce read-only henceforth */
+ igt_assert(mprotect(space, total, PROT_READ) == 0);
If rhandle was still alive, would this trigger the mmu notifier
invalidation? Something to check maybe, if there is such hook.
But from rhandle's point of view, not much happens. It's just a regular
invalidation and recovery, I think covered by the mmap-invalidate tests.
Yeah looks like that test_invalidate_close_race implies mmu notifier is
indeed invoked on pgprot changes. So it's good.
+
+ /* Check that we disallow removing the readonly protection */
What does it mean that we are disallowing it? Is it more that we are
oblivious to it (form the userptr bo point of view)?
No, that mprotect(PROT_WRITE) reports an error if you try to change the
protection from PROT_READ, so you are not allowed to create
mmap_gtt(PROT_WRITE) into a read-only userptr, nor are you allowed to
get around that restriction by changing the CPU PTE protection later.
Ah so disallowed by the core kernel? I missed that is how things work.
Regards,
Tvrtko
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