| Message ID | 1645646253-16072-1-git-send-email-vijayb@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] arm64: Do not defer reserve_crashkernel() for platforms with no DMA memory zones | expand |
On Wed, Feb 23, 2022 at 11:57:33AM -0800, Vijay Balakrishna wrote: > 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 > --- > Changes from v1 -> v2 > --------------------- > - replaced '!crashk_res.end' with IS_ENABLED(ZONE_DMA/DMA32) (Nicolas's comment) > - minor change to make it uniform -- replaced #if defined(..) -> #if IS_ENABLED(..) > - added new comment in arch/arm64/mm/init.c to ease future maintenance (Nicolas's comment) > - test performed comment moved to commit message > > [v1] https://lore.kernel.org/all/1645056294-6509-1-git-send-email-vijayb@linux.microsoft.com/ > --- > arch/arm64/mm/init.c | 36 +++++++++++++++++++++++++++++++++--- > arch/arm64/mm/mmu.c | 29 ++++++++++++++++++++++++++++- > 2 files changed, 61 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index db63cc885771..51869f9dfc33 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -61,8 +61,34 @@ EXPORT_SYMBOL(memstart_addr); > * unless restricted on specific platforms (e.g. 30-bit on Raspberry Pi 4). > * In such case, ZONE_DMA32 covers the rest of the 32-bit addressable memory, > * otherwise it is empty. > + * > + * Memory reservation for crash kernel either done early or deferred > + * depending on DMA memory zones configs (ZONE_DMA) -- > + * > + * In absence of ZONE_DMA configs arm64_dma_phys_limit initialized > + * here instead of max_zone_phys(). This lets early reservation of > + * crash kernel memory which has a dependency on arm64_dma_phys_limit. > + * Reserving memory early for crash kernel allows linear creation of block > + * mappings (greater than page-granularity) for all the memory bank rangs. > + * In this scheme a comparatively quicker boot is observed. > + * > + * If ZONE_DMA configs are defined, crash kernel memory reservation > + * is delayed until DMA zone memory range size initilazation performed in > + * zone_sizes_init(). The defer is necessary to steer clear of DMA zone > + * memory range to avoid overlap allocation. So crash kernel memory boundaries > + * are not known when mapping all bank memory ranges, which otherwise means > + * not possible to exclude crash kernel range from creating block mappings > + * so page-granularity mappings are created for the entire memory range. > + * Hence a slightly slower boot is observed. > + * > + * Note: Page-granularity mapppings are necessary for crash kernel memory > + * range for shrinking its size via /sys/kernel/kexec_crash_size interface. > */ > -phys_addr_t arm64_dma_phys_limit __ro_after_init; > +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) > +phys_addr_t __ro_after_init arm64_dma_phys_limit; > +#else > +phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; > +#endif > > #ifdef CONFIG_KEXEC_CORE > /* > @@ -153,8 +179,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) > if (!arm64_dma_phys_limit) > arm64_dma_phys_limit = dma32_phys_limit; > #endif > - if (!arm64_dma_phys_limit) > - arm64_dma_phys_limit = PHYS_MASK + 1; > max_zone_pfns[ZONE_NORMAL] = max; > > free_area_init(max_zone_pfns); > @@ -315,6 +339,10 @@ void __init arm64_memblock_init(void) > > early_init_fdt_scan_reserved_mem(); > > +#if !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32) > + reserve_crashkernel(); > +#endif Nit: with IS_ENABLED() this does not need to be an #ifdef, but rather if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32)) reserve_crashkernel(); The same applies to the cases below. > + > high_memory = __va(memblock_end_of_DRAM() - 1) + 1; > } > > @@ -357,11 +385,13 @@ void __init bootmem_init(void) > */ > dma_contiguous_reserve(arm64_dma_phys_limit); > > +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) > /* > * request_standard_resources() depends on crashkernel's memory being > * reserved, so do it here. > */ > reserve_crashkernel(); > +#endif > > memblock_dump_all(); > } > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index acfae9b41cc8..884b2c6d6cd9 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 +528,18 @@ static void __init map_mem(pgd_t *pgdp) > */ > memblock_mark_nomap(kernel_start, kernel_end - kernel_start); > > +#if IS_ENABLED(CONFIG_KEXEC_CORE) > + > +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) > + if (crash_mem_map) > + flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > +#else > + if (crashk_res.end) > + memblock_mark_nomap(crashk_res.start, > + resource_size(&crashk_res)); > +#endif > + > +#endif > /* map all the memory banks */ > for_each_mem_range(i, &start, &end) { > if (start >= end) > @@ -554,6 +566,21 @@ 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); > +#if IS_ENABLED(CONFIG_KEXEC_CORE) && \ > + !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32) > + /* > + * 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. > + */ > + 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) > -- > 2.35.1 >
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index db63cc885771..51869f9dfc33 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -61,8 +61,34 @@ EXPORT_SYMBOL(memstart_addr); * unless restricted on specific platforms (e.g. 30-bit on Raspberry Pi 4). * In such case, ZONE_DMA32 covers the rest of the 32-bit addressable memory, * otherwise it is empty. + * + * Memory reservation for crash kernel either done early or deferred + * depending on DMA memory zones configs (ZONE_DMA) -- + * + * In absence of ZONE_DMA configs arm64_dma_phys_limit initialized + * here instead of max_zone_phys(). This lets early reservation of + * crash kernel memory which has a dependency on arm64_dma_phys_limit. + * Reserving memory early for crash kernel allows linear creation of block + * mappings (greater than page-granularity) for all the memory bank rangs. + * In this scheme a comparatively quicker boot is observed. + * + * If ZONE_DMA configs are defined, crash kernel memory reservation + * is delayed until DMA zone memory range size initilazation performed in + * zone_sizes_init(). The defer is necessary to steer clear of DMA zone + * memory range to avoid overlap allocation. So crash kernel memory boundaries + * are not known when mapping all bank memory ranges, which otherwise means + * not possible to exclude crash kernel range from creating block mappings + * so page-granularity mappings are created for the entire memory range. + * Hence a slightly slower boot is observed. + * + * Note: Page-granularity mapppings are necessary for crash kernel memory + * range for shrinking its size via /sys/kernel/kexec_crash_size interface. */ -phys_addr_t arm64_dma_phys_limit __ro_after_init; +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) +phys_addr_t __ro_after_init arm64_dma_phys_limit; +#else +phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; +#endif #ifdef CONFIG_KEXEC_CORE /* @@ -153,8 +179,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) if (!arm64_dma_phys_limit) arm64_dma_phys_limit = dma32_phys_limit; #endif - if (!arm64_dma_phys_limit) - arm64_dma_phys_limit = PHYS_MASK + 1; max_zone_pfns[ZONE_NORMAL] = max; free_area_init(max_zone_pfns); @@ -315,6 +339,10 @@ void __init arm64_memblock_init(void) early_init_fdt_scan_reserved_mem(); +#if !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32) + reserve_crashkernel(); +#endif + high_memory = __va(memblock_end_of_DRAM() - 1) + 1; } @@ -357,11 +385,13 @@ void __init bootmem_init(void) */ dma_contiguous_reserve(arm64_dma_phys_limit); +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) /* * request_standard_resources() depends on crashkernel's memory being * reserved, so do it here. */ reserve_crashkernel(); +#endif memblock_dump_all(); } diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index acfae9b41cc8..884b2c6d6cd9 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 +528,18 @@ static void __init map_mem(pgd_t *pgdp) */ memblock_mark_nomap(kernel_start, kernel_end - kernel_start); +#if IS_ENABLED(CONFIG_KEXEC_CORE) + +#if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32) + if (crash_mem_map) + flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; +#else + if (crashk_res.end) + memblock_mark_nomap(crashk_res.start, + resource_size(&crashk_res)); +#endif + +#endif /* map all the memory banks */ for_each_mem_range(i, &start, &end) { if (start >= end) @@ -554,6 +566,21 @@ 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); +#if IS_ENABLED(CONFIG_KEXEC_CORE) && \ + !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32) + /* + * 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. + */ + 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)
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 --- Changes from v1 -> v2 --------------------- - replaced '!crashk_res.end' with IS_ENABLED(ZONE_DMA/DMA32) (Nicolas's comment) - minor change to make it uniform -- replaced #if defined(..) -> #if IS_ENABLED(..) - added new comment in arch/arm64/mm/init.c to ease future maintenance (Nicolas's comment) - test performed comment moved to commit message [v1] https://lore.kernel.org/all/1645056294-6509-1-git-send-email-vijayb@linux.microsoft.com/ --- arch/arm64/mm/init.c | 36 +++++++++++++++++++++++++++++++++--- arch/arm64/mm/mmu.c | 29 ++++++++++++++++++++++++++++- 2 files changed, 61 insertions(+), 4 deletions(-)