ACK/Cmnt: [PATCH][SRU][HWE BIONIC][DISCO][V2] x86/mm: Sync also unmappings in vmalloc_sync_all()

[Stefan Bader]

On 28.07.19 15:06, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1838115
> 
> 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 and make sure
> vmalloc_sync_all() iterates over all page-tables even when an unmapped PMD
> is found.
> 
> Fixes: 5d72b4fba40ef ('x86, mm: support huge I/O mapping capability I/F')
> Signed-off-by: Joerg Roedel <jroedel at suse.de>
> Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
> Reviewed-by: Dave Hansen <dave.hansen at linux.intel.com>
> Link: https://lkml.kernel.org/r/20190719184652.11391-3-joro@8bytes.org
> (backported from commit 8e998fc24de47c55b47a887f6c95ab91acd4a720)
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---

Added a disco nomination to the bug report. This probably is also something that
affects Eoan as long as they did not yet upgrade to 5.3.

-Stefan

>  arch/x86/mm/fault.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 9d5c75f..eb246b3 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -193,11 +193,12 @@ 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);
> +
> +	if (!pmd_present(*pmd_k))
> +		return NULL;
>  	else
>  		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
>  
> @@ -219,17 +220,13 @@ void vmalloc_sync_all(void)
>  		spin_lock(&pgd_lock);
>  		list_for_each_entry(page, &pgd_list, lru) {
>  			spinlock_t *pgt_lock;
> -			pmd_t *ret;
>  
>  			/* the pgt_lock only for Xen */
>  			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
>  
>  			spin_lock(pgt_lock);
> -			ret = vmalloc_sync_one(page_address(page), address);
> +			vmalloc_sync_one(page_address(page), address);
>  			spin_unlock(pgt_lock);
> -
> -			if (!ret)
> -				break;
>  		}
>  		spin_unlock(&pgd_lock);
>  	}
> 


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