On 9/4/19 9:53 AM, Daniel Vetter wrote:
On Wed, Sep 4, 2019 at 8:49 AM Thomas Hellström (VMware)
<thomas_os@xxxxxxxxxxxx> wrote:
On 9/4/19 1:15 AM, Andy Lutomirski wrote:
But, reading this, I have more questions:
Can’t you get rid of cvma by using vmf_insert_pfn_prot()?
It looks like that, although there are comments in the code about
serious performance problems using VM_PFNMAP / vmf_insert_pfn() with
write-combining and PAT, so that would require some serious testing with
hardware I don't have. But I guess there is definitely room for
improvement here. Ideally we'd like to be able to change the
vma->vm_page_prot within fault(). But we can
Just a quick comment on this: It's the repeated (per-pfn/pte) lookup
of the PAT tables, which are dead slow. If you have a struct
io_mapping then that can be done once, and then just blindly inserted.
See remap_io_mapping in i915.
-Daniel
Thanks, Daniel.
Indeed looks a lot like remap_pfn_range(), but usable at fault time?
/Thomas
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