Messages in this thread Patch in this message | | | From | Song Liu <> | Subject | [PATCH] x86/mm/pti: in pti_clone_pgtable() don't increase addr by PUD_SIZE | Date | Tue, 20 Aug 2019 00:51:28 -0700 |
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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: stable@vger.kernel.org # v4.19+ Fixes: 16a3fe634f6a ("x86/mm/pti: Clone kernel-image on PTE level for 32 bit") Signed-off-by: Song Liu <songliubraving@fb.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> --- 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
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