Hari Bathini <hbath...@linux.ibm.com> writes:
> When KFENCE is enabled, total system memory is mapped at page level
> granularity. But in radix MMU mode, ~3GB additional memory is needed
> to map 100GB of system memory at page level granularity when compared
> to using 2MB direct mapping. This is not desired considering KFENCE is
> designed to be enabled in production kernels [1]. Also, mapping memory
> allocated for KFENCE pool at page granularity seems sufficient enough
> to enable KFENCE support. So, allocate __kfence_pool during bootup and
> map it at page granularity instead of mapping all system memory at
> page granularity.
>
> Without patch:
> # cat /proc/meminfo
> MemTotal: 101201920 kB
>
> With patch:
> # cat /proc/meminfo
> MemTotal: 104483904 kB
>
> All kfence_test.c testcases passed with this patch.
>
> [1] https://lore.kernel.org/all/20201103175841.3495947-2-el...@google.com/
>
> Signed-off-by: Hari Bathini <hbath...@linux.ibm.com>
> ---
> arch/powerpc/include/asm/kfence.h | 5 ++++
> arch/powerpc/mm/book3s64/radix_pgtable.c | 34 ++++++++++++++++++------
> arch/powerpc/mm/init_64.c | 14 ++++++++++
New at this. But the patch looked interesting, hence my review comments.
> 3 files changed, 45 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kfence.h
> b/arch/powerpc/include/asm/kfence.h
> index 424ceef82ae6..18ec2b06ba1e 100644
> --- a/arch/powerpc/include/asm/kfence.h
> +++ b/arch/powerpc/include/asm/kfence.h
> @@ -8,6 +8,7 @@
> #ifndef __ASM_POWERPC_KFENCE_H
> #define __ASM_POWERPC_KFENCE_H
>
> +#include <linux/kfence.h>
> #include <linux/mm.h>
> #include <asm/pgtable.h>
>
> @@ -15,6 +16,10 @@
> #define ARCH_FUNC_PREFIX "."
> #endif
>
> +#ifdef CONFIG_KFENCE
> +extern bool kfence_early_init;
> +#endif
> +
> static inline bool arch_kfence_init_pool(void)
> {
> return true;
Shouldn't we return false for !kfence_early_init?
Because otherwise, this patch may break the late init case which your
next patch is fixing, and maybe git bisect will break?
> diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c
> b/arch/powerpc/mm/book3s64/radix_pgtable.c
> index 15e88f1439ec..fccbf92f279b 100644
> --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> @@ -31,6 +31,7 @@
> #include <asm/uaccess.h>
> #include <asm/ultravisor.h>
> #include <asm/set_memory.h>
> +#include <asm/kfence.h>
>
> #include <trace/events/thp.h>
>
> @@ -291,9 +292,8 @@ static unsigned long next_boundary(unsigned long addr,
> unsigned long end)
> return end;
> }
>
> -static int __meminit create_physical_mapping(unsigned long start,
> - unsigned long end,
> - int nid, pgprot_t _prot)
> +static int __meminit create_physical_mapping(unsigned long start, unsigned
> long end, int nid,
> + pgprot_t _prot, unsigned long
> mapping_sz_limit)
lines over 80 chars.
> {
> unsigned long vaddr, addr, mapping_size = 0;
> bool prev_exec, exec = false;
> @@ -301,7 +301,10 @@ static int __meminit create_physical_mapping(unsigned
> long start,
> int psize;
> unsigned long max_mapping_size = memory_block_size;
>
> - if (debug_pagealloc_enabled_or_kfence())
> + if (mapping_sz_limit < max_mapping_size)
> + max_mapping_size = mapping_sz_limit;
> +
> + if (debug_pagealloc_enabled())
> max_mapping_size = PAGE_SIZE;
>
> start = ALIGN(start, PAGE_SIZE);
> @@ -358,6 +361,7 @@ static int __meminit create_physical_mapping(unsigned
> long start,
>
> static void __init radix_init_pgtable(void)
> {
> + phys_addr_t kfence_pool __maybe_unused;
> unsigned long rts_field;
> phys_addr_t start, end;
> u64 i;
> @@ -365,6 +369,13 @@ static void __init radix_init_pgtable(void)
> /* We don't support slb for radix */
> slb_set_size(0);
>
> +#ifdef CONFIG_KFENCE
> + if (kfence_early_init) {
> + kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE);
What if memblock_phys_alloc() failed? error handling?
> + memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE);
> + }
> +#endif
> +
Instead of #ifdef CONFIG_KFENCE in the function,
maybe we can define radix_kfence_alloc_pool()? Then we won't need
__maybe_unused too.
> /*
> * Create the linear mapping
> */
> @@ -380,10 +391,18 @@ static void __init radix_init_pgtable(void)
> continue;
> }
>
> - WARN_ON(create_physical_mapping(start, end,
> - -1, PAGE_KERNEL));
> + WARN_ON(create_physical_mapping(start, end, -1, PAGE_KERNEL,
> ~0UL));
> }
>
> +#ifdef CONFIG_KFENCE
> + if (kfence_early_init) {
> + create_physical_mapping(kfence_pool, kfence_pool +
> KFENCE_POOL_SIZE, -1,
> + PAGE_KERNEL, PAGE_SIZE);
Even this can return an error. Maybe WARN_ON_ONCE()? or disabling kfence
for an error?
> + memblock_clear_nomap(kfence_pool, KFENCE_POOL_SIZE);
> + __kfence_pool = __va(kfence_pool);
> + }
> +#endif
> +
This #ifdef can be called as radix_kfence_map_pool() then?
> if (!cpu_has_feature(CPU_FTR_HVMODE) &&
> cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG)) {
> /*
> @@ -874,8 +893,7 @@ int __meminit radix__create_section_mapping(unsigned long
> start,
> return -1;
> }
>
> - return create_physical_mapping(__pa(start), __pa(end),
> - nid, prot);
> + return create_physical_mapping(__pa(start), __pa(end), nid, prot, ~0UL);
> }
>
> int __meminit radix__remove_section_mapping(unsigned long start, unsigned
> long end)
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index d96bbc001e73..8155bfd6c16b 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -64,6 +64,20 @@
>
> #include <mm/mmu_decl.h>
>
> +#ifdef CONFIG_KFENCE
> +bool __ro_after_init kfence_early_init = !!CONFIG_KFENCE_SAMPLE_INTERVAL;
> +
> +static int __init parse_kfence_early_init(char *arg)
> +{
> + int val;
> +
> + if (get_option(&arg, &val))
> + kfence_early_init = !!val;
> + return 0;
> +}
> +early_param("kfence.sample_interval", parse_kfence_early_init);
> +#endif
> +
> #ifdef CONFIG_SPARSEMEM_VMEMMAP
> /*
> * Given an address within the vmemmap, determine the page that
> --
> 2.44.0
