Messages in this thread | | | Subject | Re: [PATCH v1 4/4] Revert "arm64: Enforce BBM for huge IO/VMAP mappings" | From | Chintan Pandya <> | Date | Wed, 14 Mar 2018 17:02:33 +0530 |
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On 3/14/2018 4:16 PM, Marc Zyngier wrote: > On 14/03/18 08:48, Chintan Pandya wrote: >> This commit 15122ee2c515a ("arm64: Enforce BBM for huge >> IO/VMAP mappings") is a temporary work-around until the >> issues with CONFIG_HAVE_ARCH_HUGE_VMAP gets fixed. >> >> Revert this change as we have fixes for the issue. >> >> Signed-off-by: Chintan Pandya <cpandya@codeaurora.org> >> --- >> arch/arm64/mm/mmu.c | 8 -------- >> 1 file changed, 8 deletions(-) >> >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index c0df264..19116c6 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -935,10 +935,6 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot) >> pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT | >> pgprot_val(mk_sect_prot(prot))); >> >> - /* ioremap_page_range doesn't honour BBM */ >> - if (pud_present(READ_ONCE(*pudp))) >> - return 0; >> - >> BUG_ON(phys & ~PUD_MASK); >> if (pud_val(*pud) && !pud_huge(*pud)) >> free_page((unsigned long)__va(pud_val(*pud))); >> @@ -952,10 +948,6 @@ int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot) >> pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT | >> pgprot_val(mk_sect_prot(prot))); >> >> - /* ioremap_page_range doesn't honour BBM */ >> - if (pmd_present(READ_ONCE(*pmdp))) >> - return 0; >> - >> BUG_ON(phys & ~PMD_MASK); >> if (pmd_val(*pmd) && !pmd_huge(*pmd)) >> free_page((unsigned long)__va(pmd_val(*pmd))); >> > > But you're still not doing a BBM, right? What prevents a speculative > access from using the (now freed) entry? The TLB invalidation you've > introduce just narrows the window where bad things can happen. Valid point. I will rework on these patches.
Thanks Marc.
> > My gut feeling is that this series introduces more bugs than it fixes... > If you're going to fix it, please fix it by correctly implementing BBM > for huge mappings. > > Or am I missing something terribly obvious? > > M. >
Chintan -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
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