On 28.06.2018 11:17, Christian Borntraeger wrote:
>
>
> On 06/27/2018 03:55 PM, Janosch Frank wrote:
>> From: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
>>
>> When changing guest pmds, we don't need to take care of the
>> corresponding host pmd. This means, we don't need to flush the host
>> TLB entries and we don't need to notify on all gmaps.
>>
>> Let's introduce a function, that exchanges a pmd and takes care of the
>> necessary flushing.
>>
>> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
>> ---
>> arch/s390/mm/gmap.c | 26 ++++++++++++++++++++++++++
>> 1 file changed, 26 insertions(+)
>>
>> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
>> index bae0b4f674b5..f5b48426dde8 100644
>> --- a/arch/s390/mm/gmap.c
>> +++ b/arch/s390/mm/gmap.c
>> @@ -23,6 +23,9 @@
>>
>> #define GMAP_SHADOW_FAKE_TABLE 1ULL
>>
>> +static void gmap_pmdp_xchg(struct gmap *gmap, pmd_t *old, pmd_t new,
>> + unsigned long gaddr);
>> +
>> /**
>> * gmap_alloc - allocate and initialize a guest address space
>> * @mm: pointer to the parent mm_struct
>> @@ -2165,6 +2168,29 @@ void ptep_notify(struct mm_struct *mm, unsigned long vmaddr,
>> }
>> EXPORT_SYMBOL_GPL(ptep_notify);
>>
>> +/**
>> + * gmap_pmdp_xchg - exchange a gmap pmd with another
>> + * @gmap: pointer to the guest address space structure
>> + * @pmdp: pointer to the pmd entry
>> + * @new: replacement entry
>> + * @gaddr: the affected guest address
>> + *
>> + * This function is assumed to be called with the guest_table_lock
>> + * held.
>> + */
>> +static void gmap_pmdp_xchg(struct gmap *gmap, pmd_t *pmdp, pmd_t new,
>> + unsigned long gaddr)
>> +{
>> + if (MACHINE_HAS_TLB_GUEST)
>> + __pmdp_idte(gaddr, (pmd_t *)pmdp, IDTE_GUEST_ASCE, gmap->asce,
>> + IDTE_GLOBAL);
>
> do we need an else here?
Good catch
It would be better to have one and avoid the second IDTE.
>
>> + if (MACHINE_HAS_IDTE)
>> + __pmdp_idte(gaddr, (pmd_t *)pmdp, 0, 0, IDTE_GLOBAL);
>
>
>> + else
>> + __pmdp_csp(pmdp);
>> + *pmdp = new;
>> +}
>> +
>> static inline void thp_split_mm(struct mm_struct *mm)
>> {
>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>
>
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