On 22/07/16 17:27, Ard Biesheuvel wrote:
On 22 July 2016 at 16:30, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
Hi Ard,
On 29/06/16 13:51, Ard Biesheuvel wrote:
To avoid triggering diagnostics in the MMU code that are finicky about
splitting block mappings into more granular mappings, ensure that regions
that are likely to appear in the Memory Attributes table as well as the
UEFI memory map are always mapped down to pages. This way, we can use
apply_to_page_range() instead of create_pgd_mapping() for the second pass,
which cannot split or merge block entries, and operates strictly on PTEs.
Note that this aligns the arm64 Memory Attributes table handling code with
the ARM code, which already uses apply_to_page_range() to set the strict
permissions.
This patch is merged in arm64/for-next/core now and when I try that
branch with defconfig + CONFIG_PROVE_LOCKING, I get the following splat
on boot and it fails to boot further on Juno.
I could bisect that to this patch(Commit bd264d046aad ("arm64: efi:
always map runtime services code and data regions down to pages") in
that branch)
Hi Sudeep,
I can reproduce this on QEMU as well. It appears that
apply_to_page_range() expects pages containing translation tables to
have their per-page spinlock initialized if they are not part of
init_mm.
This
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -272,6 +272,7 @@ static phys_addr_t late_pgtable_alloc(void)
{
void *ptr = (void *)__get_free_page(PGALLOC_GFP);
BUG_ON(!ptr);
+ BUG_ON(!pgtable_page_ctor(virt_to_page(ptr)));
/* Ensure the zeroed page is visible to the page table walker */
dsb(ishst);
makes the problem go away for me (just as a temporary hack) but I will
try to come up with something more appropriate, and check if ARM has
the same issue (since it uses apply_to_page_range() as well)
Ard,
I took a quick look at it. Looks like we don't initialise the page-table
pages allocated via late_pgtable_alloc. Since we allocate it for an mm != init_mm,
the lock validator comes into picture and finds a lock which is not initialised.
The following patch fixes the issue. But is not a perfect one. May need to polish it
a little bit.
----8>----
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a96a241..d312667 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -270,12 +270,12 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
static phys_addr_t late_pgtable_alloc(void)
{
- void *ptr = (void *)__get_free_page(PGALLOC_GFP);
- BUG_ON(!ptr);
+ struct page *page = pte_alloc_one(NULL, 0);
+ BUG_ON(!page);
/* Ensure the zeroed page is visible to the page table walker */
dsb(ishst);
- return __pa(ptr);
+ return __pa(page_address(page));
}
Thanks
Suzuki
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