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SubjectRe: [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync_one()
On Mon, 15 Jul 2019, Joerg Roedel wrote:

> From: Joerg Roedel <jroedel@suse.de>
>
> With huge-page ioremap areas the unmappings also need to be
> synced between all page-tables. Otherwise it can cause data
> corruption when a region is unmapped and later re-used.
>
> Make the vmalloc_sync_one() function ready to sync
> unmappings.
>
> Signed-off-by: Joerg Roedel <jroedel@suse.de>

Lacks a Fixes tag methinks.

> ---
> arch/x86/mm/fault.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 4a4049f6d458..d71e167662c3 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -194,11 +194,12 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
>
> pmd = pmd_offset(pud, address);
> pmd_k = pmd_offset(pud_k, address);
> - if (!pmd_present(*pmd_k))
> - return NULL;
>
> - if (!pmd_present(*pmd))
> + if (pmd_present(*pmd) ^ pmd_present(*pmd_k))
> set_pmd(pmd, *pmd_k);

It took me a while to understand what this is doing. Can we please have a
comment here?

> +
> + if (!pmd_present(*pmd_k))
> + return NULL;

Thanks,

tglx

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