Hi,
On 13/08/2020 17:08, Hongyan Xia wrote:
On Fri, 2020-08-07 at 16:05 +0200, Jan Beulich wrote:
On 27.07.2020 16:21, Hongyan Xia wrote:
From: Wei Liu <wei.l...@citrix.com>
Rewrite those functions to use the new APIs. Modify its callers to
unmap
the pointer returned. Since alloc_xen_pagetable_new() is almost
never
useful unless accompanied by page clearing and a mapping, introduce
a
helper alloc_map_clear_xen_pt() for this sequence.
Note that the change of virt_to_xen_l1e() also requires
vmap_to_mfn() to
unmap the page, which requires domain_page.h header in vmap.
Signed-off-by: Wei Liu <wei.l...@citrix.com>
Signed-off-by: Hongyan Xia <hongy...@amazon.com>
Reviewed-by: Jan Beulich <jbeul...@suse.com>
---
Changed in v8:
- s/virtual address/linear address/.
- BUG_ON() on NULL return in vmap_to_mfn().
The justification for this should be recorded in the description. In
Will do.
reply to v7 I did even suggest how to easily address the issue you
did notice with large pages, as well as alternative behavior for
vmap_to_mfn().
One thing about adding SMALL_PAGES is that vmap is common code and I am
not sure if the Arm side is happy with it.
At the moment, Arm is only using small mapping but I plan to change that
soon because we have regions that can be fairly big.
Regardless that, the issue with vmap_to_mfn() is rather x86 specific. So
I don't particularly like the idea to expose such trick in common code.
Even on x86, I think this is not the right approach. Such band-aid will
impact the performance as, assuming superpages are used, it will take
longer to map and add pressure on the TLBs.
I am aware that superpages will be useful for LiveUpdate, but is there
any use cases in upstream? If not, could we just use the BUG_ON() and
implement correctly vmap_to_mfn() in a follow-up?
Cheers,
--
Julien Grall
