On 10/14/22 13:22, Xenia Ragiadakou wrote:
On 10/14/22 13:04, Julien Grall wrote:
Hi Xenia,
On 14/10/2022 10:46, Xenia Ragiadakou wrote:
On 10/13/22 15:39, Julien Grall wrote:
Hi,
On 13/10/2022 13:29, Henry Wang wrote:
-----Original Message-----
From: Jan Beulich <jbeul...@suse.com>
Assuming you have 4 (N) page table levels, isn't it 7 (1 + 2 *
(N - 1))?
Or is the root table not taken from the p2m pool?
Correct, on arm the root is not taken from the pool.
Isn't that a (perhaps just minor) mistake?
Not really, in the code review phase, the question of whether we
include
the root in the p2m pool was discussed and the conclusion at that time
was not including this page for now, as this is supposed to require
a lot
of extra work/refactor. Probably there will be a series from my
side to
add the root to the pool, but at least not now.
The root page tables can be one of multiple concatenated pages (up
to 8 pages). The P2M pool is allocating page by page and therefore
wouldn't allow us to allocate contiguous pages.
Sorry that I 'm asking this so late (I was just going through the
thread) but why 8?
Rather than providing an extra level of page-tables, the architecture
allows you to provide multiple pages at the root level.
The number of concatenated pages depend on the maximum physical
address and the start level. You can look at the table in
setup_virt_paging() for more details.
I think you are referring to this:
[6] = { 52, 12/*12*/, 3, 3 },
Still I cannot understand why the maximum number of concatenated level 0
translation tables for t0sz 12 and 4KB granule is 8 and not 16?
Let me explain. Initially I got confused because according to the manual
up to 16 translation tables can be concatenated. Then, looking at the
code you have pointed out, I understood that you were referring to the
maximum root order in the table below.
pa_range_info[] = {
/* T0SZ minimum and SL0 maximum from ARM DDI 0487H.a Table D5-6 */
/* PA size, t0sz(min), root-order, sl0(max) */
[0] = { 32, 32/*32*/, 0, 1 },
[1] = { 36, 28/*28*/, 0, 1 },
[2] = { 40, 24/*24*/, 1, 1 },
[3] = { 42, 22/*22*/, 3, 1 },
[4] = { 44, 20/*20*/, 0, 2 },
[5] = { 48, 16/*16*/, 0, 2 },
[6] = { 52, 12/*12*/, 3, 3 },
[7] = { 0 } /* Invalid */
};
I think that the pa range info for the 52-bit pa range is wrong.
IMO, it could be either
[6] = { 52, 12/*12*/, 0, 3 } i.e single level -1 table
or
[6] = { 52, 12/*12*/, 4, 2 } i.e 16 concatenated level 0
tables
Hope I am not totally out of context.
Cheers,
--
Xenia
