pti_clone_pgtable() increases addr by PUD_SIZE for pud_none(*pud) case. This is not accurate because addr may not be PUD_SIZE aligned.
In our x86_64 kernel, pti_clone_pgtable() fails to clone 7 PMDs because of this issuse, including PMD for the irq entry table. For a memcache like workload, this introduces about 4.5x more iTLB-load and about 2.5x more iTLB-load-misses on a Skylake CPU. This patch fixes this issue by adding PMD_SIZE to addr for pud_none() case. Cc: [email protected] # v4.19+ Fixes: 16a3fe634f6a ("x86/mm/pti: Clone kernel-image on PTE level for 32 bit") Signed-off-by: Song Liu <[email protected]> Cc: Joerg Roedel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Peter Zijlstra <[email protected]> --- arch/x86/mm/pti.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index b196524759ec..5a67c3015f59 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -330,7 +330,7 @@ pti_clone_pgtable(unsigned long start, unsigned long end, pud = pud_offset(p4d, addr); if (pud_none(*pud)) { - addr += PUD_SIZE; + addr += PMD_SIZE; continue; } -- 2.17.1
