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| author |   Vijay Balakrishna <vijayb@linux.microsoft.com> | 2022-03-02 09:38:09 -0800 |
|---|---|---|
| committer |   Will Deacon <will@kernel.org> | 2022-03-08 10:22:33 +0000 |
| commit | 031495635b4668f94e964e037ca93d0d38bfde58 (patch) | |
| tree | a1d2a3396f579935b8f8e1dd33900be684e09030 /arch/arm64/mm/mmu.c | |
| parent | arm64: prevent instrumentation of bp hardening callbacks (diff) | |
| download | linux-dev-031495635b4668f94e964e037ca93d0d38bfde58.tar.xz linux-dev-031495635b4668f94e964e037ca93d0d38bfde58.zip | |
arm64: Do not defer reserve_crashkernel() for platforms with no DMA memory zones
The following patches resulted in deferring crash kernel reservation to
mem_init(), mainly aimed at platforms with DMA memory zones (no IOMMU),
in particular Raspberry Pi 4.
commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32")
commit 8424ecdde7df ("arm64: mm: Set ZONE_DMA size based on devicetree's dma-ranges")
commit 0a30c53573b0 ("arm64: mm: Move reserve_crashkernel() into mem_init()")
commit 2687275a5843 ("arm64: Force NO_BLOCK_MAPPINGS if crashkernel reservation is required")
Above changes introduced boot slowdown due to linear map creation for
all the memory banks with NO_BLOCK_MAPPINGS, see discussion[1]. The proposed
changes restore crash kernel reservation to earlier behavior thus avoids
slow boot, particularly for platforms with IOMMU (no DMA memory zones).
Tested changes to confirm no ~150ms boot slowdown on our SoC with IOMMU
and 8GB memory. Also tested with ZONE_DMA and/or ZONE_DMA32 configs to confirm
no regression to deferring scheme of crash kernel memory reservation.
In both cases successfully collected kernel crash dump.
[1] https://lore.kernel.org/all/9436d033-579b-55fa-9b00-6f4b661c2dd7@linux.microsoft.com/
Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: stable@vger.kernel.org
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/r/1646242689-20744-1-git-send-email-vijayb@linux.microsoft.com
[will: Add #ifdef CONFIG_KEXEC_CORE guards to fix 'crashk_res' references in allnoconfig build]
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/mm/mmu.c')
| -rw-r--r-- | arch/arm64/mm/mmu.c | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index acfae9b41cc8..ed21bf83d0b7 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -517,7 +517,7 @@ static void __init map_mem(pgd_t *pgdp) */ BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end)); - if (can_set_direct_map() || crash_mem_map || IS_ENABLED(CONFIG_KFENCE)) + if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; /* @@ -528,6 +528,17 @@ static void __init map_mem(pgd_t *pgdp) */ memblock_mark_nomap(kernel_start, kernel_end - kernel_start); +#ifdef CONFIG_KEXEC_CORE + if (crash_mem_map) { + if (IS_ENABLED(CONFIG_ZONE_DMA) || + IS_ENABLED(CONFIG_ZONE_DMA32)) + flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; + else if (crashk_res.end) + memblock_mark_nomap(crashk_res.start, + resource_size(&crashk_res)); + } +#endif + /* map all the memory banks */ for_each_mem_range(i, &start, &end) { if (start >= end) @@ -554,6 +565,25 @@ static void __init map_mem(pgd_t *pgdp) __map_memblock(pgdp, kernel_start, kernel_end, PAGE_KERNEL, NO_CONT_MAPPINGS); memblock_clear_nomap(kernel_start, kernel_end - kernel_start); + + /* + * Use page-level mappings here so that we can shrink the region + * in page granularity and put back unused memory to buddy system + * through /sys/kernel/kexec_crash_size interface. + */ +#ifdef CONFIG_KEXEC_CORE + if (crash_mem_map && + !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32)) { + if (crashk_res.end) { + __map_memblock(pgdp, crashk_res.start, + crashk_res.end + 1, + PAGE_KERNEL, + NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS); + memblock_clear_nomap(crashk_res.start, + resource_size(&crashk_res)); + } + } +#endif } void mark_rodata_ro(void) |