| Message ID | 1645056294-6509-1-git-send-email-vijayb@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Do not defer reserve_crashkernel() for platforms with no DMA memory zones | expand |
On Wed, 2022-02-16 at 16:04 -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). > > [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 > --- > 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. > --- > arch/arm64/mm/init.c | 14 +++++++++++--- > arch/arm64/mm/mmu.c | 24 +++++++++++++++++++++++- > 2 files changed, 34 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index db63cc885771..f2a982c19b75 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -62,7 +62,11 @@ EXPORT_SYMBOL(memstart_addr); > * In such case, ZONE_DMA32 covers the rest of the 32-bit addressable memory, > * otherwise it is empty. > */ > -phys_addr_t arm64_dma_phys_limit __ro_after_init; > +#if !defined(CONFIG_ZONE_DMA) && !defined(CONFIG_ZONE_DMA32) > +phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; > +#else > +phys_addr_t __ro_after_init arm64_dma_phys_limit; > +#endif > > #ifdef CONFIG_KEXEC_CORE > /* > @@ -153,8 +157,6 @@ 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 +317,10 @@ void __init arm64_memblock_init(void) > > early_init_fdt_scan_reserved_mem(); > > +#if !defined(CONFIG_ZONE_DMA) && !defined(CONFIG_ZONE_DMA32) > + reserve_crashkernel(); > +#endif > + > high_memory = __va(memblock_end_of_DRAM() - 1) + 1; > } > > @@ -357,11 +363,13 @@ void __init bootmem_init(void) > */ > dma_contiguous_reserve(arm64_dma_phys_limit); > > +#if defined(CONFIG_ZONE_DMA) || defined(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..e7faf5edccfc 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 +528,14 @@ 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 && !crashk_res.end) > + flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; Using IS_ENABLED(ZONE_DMA/DMA32) instead of '!crashk_res.end' would be more efficient and a bit more explicit IMO. > /* map all the memory banks */ > for_each_mem_range(i, &start, &end) { > if (start >= end) > @@ -554,6 +562,20 @@ 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); > +#ifdef CONFIG_KEXEC_CORE > + /* > + * 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) { Same here. > + __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 Now, I carefully reviewed the patch and it seems to be doing the right thing. But even while knowlegable on the topic, it took a good amount of effort to untangle the possible code paths. I suspect it's going to be painful to maintain. I'd suggest at least introducing a comment explaining the situation. If there approach if deemed acceptable, I'll test is on the RPi4. Regards, Nicolas
Sorry, typos:
On Thu, 2022-02-17 at 11:49 +0100, nicolas saenz julienne wrote:
> If there approach if deemed acceptable, I'll test is on the RPi4.
"If the approach is deemed acceptable,"
Regards,
Nicoals
On 2/17/2022 2:49 AM, nicolas saenz julienne wrote: > On Wed, 2022-02-16 at 16:04 -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()") .. >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index acfae9b41cc8..e7faf5edccfc 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 +528,14 @@ 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 && !crashk_res.end) >> + flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > > Using IS_ENABLED(ZONE_DMA/DMA32) instead of '!crashk_res.end' would be more > efficient and a bit more explicit IMO. Sure, I will make change in a follow up submission. > >> /* map all the memory banks */ >> for_each_mem_range(i, &start, &end) { >> if (start >= end) >> @@ -554,6 +562,20 @@ 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); >> +#ifdef CONFIG_KEXEC_CORE >> + /* >> + * 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) { > > Same here. Yes. > >> + __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 > > Now, I carefully reviewed the patch and it seems to be doing the right thing. > But even while knowlegable on the topic, it took a good amount of effort to > untangle the possible code paths. I suspect it's going to be painful to > maintain. I'd suggest at least introducing a comment explaining the situation. I appreciate your review. Yes, it took a good amount of time for me (new here) too and glad for your notice. Let me take a shot at explaining in my next revision. > > If there approach if deemed acceptable, I'll test is on the RPi4. Please, your testing on RPi4 would be valuable. Thanks, Vijay > > Regards, > Nicolas
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index db63cc885771..f2a982c19b75 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -62,7 +62,11 @@ EXPORT_SYMBOL(memstart_addr); * In such case, ZONE_DMA32 covers the rest of the 32-bit addressable memory, * otherwise it is empty. */ -phys_addr_t arm64_dma_phys_limit __ro_after_init; +#if !defined(CONFIG_ZONE_DMA) && !defined(CONFIG_ZONE_DMA32) +phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; +#else +phys_addr_t __ro_after_init arm64_dma_phys_limit; +#endif #ifdef CONFIG_KEXEC_CORE /* @@ -153,8 +157,6 @@ 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 +317,10 @@ void __init arm64_memblock_init(void) early_init_fdt_scan_reserved_mem(); +#if !defined(CONFIG_ZONE_DMA) && !defined(CONFIG_ZONE_DMA32) + reserve_crashkernel(); +#endif + high_memory = __va(memblock_end_of_DRAM() - 1) + 1; } @@ -357,11 +363,13 @@ void __init bootmem_init(void) */ dma_contiguous_reserve(arm64_dma_phys_limit); +#if defined(CONFIG_ZONE_DMA) || defined(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..e7faf5edccfc 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 +528,14 @@ 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 && !crashk_res.end) + flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; + + 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 +562,20 @@ 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); +#ifdef CONFIG_KEXEC_CORE + /* + * 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). [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 --- 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. --- arch/arm64/mm/init.c | 14 +++++++++++--- arch/arm64/mm/mmu.c | 24 +++++++++++++++++++++++- 2 files changed, 34 insertions(+), 4 deletions(-)