And very grateful for taking this patch into the mainstream.
_Best Regards_,
-Vishnu.
------------------------------------------------------------------------
*From:* Julien Grall <julien.gr...@arm.com>
*Sent:* 31 May 2019 23:22
*To:* Vishnu Pajjuri OS; xen-devel@lists.xenproject.org
*Cc:* Open Source Submission; sstabell...@kernel.org; Feng Kan OS
*Subject:* Re: [PATCH v2] xen/arm: p2m: configure stage-2 page table to
support upto 42-bit PA systems
Hi,
Title: s/upto/ I think?
Also how about: "Properly configure stage-2 for 42-bit PA system".
On 30/05/2019 08:59, Vishnu Pajjuri OS wrote:
XEN configures stage-2 page table to expose 40 bits of IPA
(Intermediate Physical Address) bits for systems with 42 bits of PA
I think you want to drop the first "bits".
(Physical Address). This setting prevents the 42-bit PA systems from booting
DOM0's kernel since access above 40 bits results in a fault.
This sentence is difficult to read if you don't read the next one first.
This patch adds support for 42-bit system
which has a full 42-bit address range.
The line-wrap looks strange here.
The fix will allocate 8 pages for stage 2 mapping for both DOM0 and guests.
s/mapping/root page-tables/
It is a bit wasteful but not an issue since most of these systems should have
sufficiently large memory capacity.
Here a suggestion for the commit message:
"At the moment, on platform supporting 42-bit PA, Xen will only expose
40-bit
worth of IPA to all domains.
The limitation was to prevent allocating too much memory for the root page
tables as those platforms only support 3-levels page-tables. At the
time, this
was deemed acceptable because none of the platforms had address wired
above 40-bits.
However, newer platforms take advantage of the full address space. This
will
result to break Dom0 boot as it can't access anything above 40-bit.
The only way to support 42-bit IPA is to allocate 8 pages for the root
page-tables. This is a bit a waste of memory as Xen does not offer
per-guest
stage-2 configuration. But it is considered acceptable as current platforms
support 42-bit PA have a lot of memory.
In the future, we may want to consider per-guest stage-2 configuration
to reduce
the waste.
"
If you are happy with the commit message, I will update use it on commit.
Signed-off-by: Feng Kan <feng...@os.amperecomputing.com>
Signed-off-by: Vishnu <vis...@os.amperecomputing.com>
---
It is common to briefly describe after --- the changes you made in the
new version.
xen/arch/arm/p2m.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 92c2413..7712991 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1995,7 +1995,7 @@ void __init setup_virt_paging(void)
[0] = { 32, 32/*32*/, 0, 1 },
[1] = { 36, 28/*28*/, 0, 1 },
[2] = { 40, 24/*24*/, 1, 1 },
- [3] = { 42, 24/*22*/, 1, 1 },
+ [3] = { 42, 22/*22*/, 3, 1 },
[4] = { 44, 20/*20*/, 0, 2 },
[5] = { 48, 16/*16*/, 0, 2 },
[6] = { 0 }, /* Invalid */
--
1.8.3.1
--
Julien Grall
