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

[Stefan Bader]

On 29.07.19 10:56, Stefan Bader wrote:
> 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.
> 

I might have been too quick. This patch seems to be 1/3 which all claim to be
fixes for the same commit. And were committed right next to each other. I
probably would be better to pick them all.

> -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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