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If the caller >> already set __GFP_SKIP_KASAN, don’t skip zeroing the pages and >> don’t set KASAN_VMALLOC_PROT_NORMAL so kasan_unpoison_vmalloc() >> returns early without tagging. >> >> Before this patch, __GFP_SKIP_KASAN wasn't being used with vmalloc >> APIs. So it wasn't being checked. Now its being checked and acted >> upon. Other KASAN modes are unchanged because __GFP_SKIP_KASAN isn't >> defined there. >> >> This is a preparatory patch for optimizing kernel stack allocations. >> >> Signed-off-by: Muhammad Usama Anjum >> --- >> mm/vmalloc.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index c607307c657a6..1baa602a0b9bb 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -4041,7 +4041,10 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, >> * kasan_unpoison_vmalloc(). >> */ >> if (pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) { >> - if (kasan_hw_tags_enabled()) { >> + bool skip_kasan = kasan_hw_tags_enabled() && >> + (gfp_mask & __GFP_SKIP_KASAN); >> + >> + if (kasan_hw_tags_enabled() && !skip_kasan) { > > It's unfortunate that kasan_hw_tags_enabled() is involved twice in this expression. I've looked at this again and simplified based on the fact tha __GFP_SKIP_KASAN is zero in other than hw-tag modes. > >> /* >> * Modify protection bits to allow tagging. >> * This must be done before mapping. >> @@ -4057,7 +4060,8 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, >> } >> >> /* Take note that the mapping is PAGE_KERNEL. */ >> - kasan_flags |= KASAN_VMALLOC_PROT_NORMAL; >> + if (!skip_kasan) >> + kasan_flags |= KASAN_VMALLOC_PROT_NORMAL; > > I wonder if it would be clearer to just not call kasan_unpoison_vmalloc() below > if the user passed in __GFP_SKIP_KASAN? It's really just an implementation > detail that kasan_unpoison_vmalloc() skips unpoisoning if > KASAN_VMALLOC_PROT_NORMAL is not provided. Then it would be confusing to set kasan_flags to KASAN_VMALLOC_PROT_NORMAL and not use it later. I've found a good of doing it this way. Thanks, Usama > > Thanks, > Ryan > > >> } >> >> /* Allocate physical pages and map them into vmalloc space. */ >