[PATCH 2/5] arm64: efi: always map runtime services code and data regions down to pages
From: Suzuki.Poulose@arm.com (Suzuki K Poulose)
Date: 2016-07-22 16:36:55
Also in:
linux-efi
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
On 22/07/16 17:27, Ard Biesheuvel wrote:
quoted hunk ↗ jump to hunk
On 22 July 2016 at 16:30, Sudeep Holla [off-list ref] wrote:quoted
Hi Ard, On 29/06/16 13:51, Ard Biesheuvel wrote:quoted
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