On 04/10/2018 07:11 PM, Hari Bathini wrote:
> FADump capture kernel boots in restricted memory environment preserving
> the context of previous kernel to save vmcore. Supporting hugepages in
> such environment makes things unnecessarily complicated, as hugepages
> need memory set aside for them. This means most of the capture kernel's
> memory is used in supporting hugepages. In most cases, this results in
> out-of-memory issues while booting FADump capture kernel. But hugepages
> are not of much use in capture kernel whose only job is to save vmcore.
> So, disabling hugepages support, when fadump is active, is a reliable
> solution for the out of memory issues. Introducing a flag variable to
> disable HugeTLB support when fadump is active.
>
> Signed-off-by: Hari Bathini <hbath...@linux.vnet.ibm.com>
> ---
>
> Changes in v2:
> * Introduce a hugetlb_disabled flag to enable/disable hugepage support &
> use that flag to disable hugepage support when fadump is active.
Looks good to me.
Reviewed-by: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com>
>
>
> arch/powerpc/include/asm/page.h | 1 +
> arch/powerpc/kernel/fadump.c | 8 ++++++++
> arch/powerpc/mm/hash_utils_64.c | 6 ++++--
> arch/powerpc/mm/hugetlbpage.c | 7 +++++++
> 4 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index 8da5d4c..40aee93 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -39,6 +39,7 @@
>
> #ifndef __ASSEMBLY__
> #ifdef CONFIG_HUGETLB_PAGE
> +extern bool hugetlb_disabled;
> extern unsigned int HPAGE_SHIFT;
> #else
> #define HPAGE_SHIFT PAGE_SHIFT
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index bea8d5f..8ceabef4 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -402,6 +402,14 @@ int __init fadump_reserve_mem(void)
> if (fw_dump.dump_active) {
> pr_info("Firmware-assisted dump is active.\n");
>
> +#ifdef CONFIG_HUGETLB_PAGE
> + /*
> + * FADump capture kernel doesn't care much about hugepages.
> + * In fact, handling hugepages in capture kernel is asking for
> + * trouble. So, disable HugeTLB support when fadump is active.
> + */
> + hugetlb_disabled = true;
> +#endif
> /*
> * If last boot has crashed then reserve all the memory
> * above boot_memory_size so that we don't touch it until
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index cf290d41..eab8f1d 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -571,8 +571,10 @@ static void __init htab_scan_page_sizes(void)
> }
>
> #ifdef CONFIG_HUGETLB_PAGE
> - /* Reserve 16G huge page memory sections for huge pages */
> - of_scan_flat_dt(htab_dt_scan_hugepage_blocks, NULL);
> + if (!hugetlb_disabled) {
> + /* Reserve 16G huge page memory sections for huge pages */
> + of_scan_flat_dt(htab_dt_scan_hugepage_blocks, NULL);
> + }
> #endif /* CONFIG_HUGETLB_PAGE */
> }
>
> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index 876da2b..18c080a 100644
> --- a/arch/powerpc/mm/hugetlbpage.c
> +++ b/arch/powerpc/mm/hugetlbpage.c
> @@ -35,6 +35,8 @@
> #define PAGE_SHIFT_16M 24
> #define PAGE_SHIFT_16G 34
>
> +bool hugetlb_disabled = false;
> +
> unsigned int HPAGE_SHIFT;
> EXPORT_SYMBOL(HPAGE_SHIFT);
>
> @@ -653,6 +655,11 @@ static int __init hugetlbpage_init(void)
> {
> int psize;
>
> + if (hugetlb_disabled) {
> + pr_info("HugeTLB support is disabled!\n");
> + return 0;
> + }
> +
> #if !defined(CONFIG_PPC_FSL_BOOK3E) && !defined(CONFIG_PPC_8xx)
> if (!radix_enabled() && !mmu_has_feature(MMU_FTR_16M_PAGE))
> return -ENODEV;
>
