| Message ID | 20231109123624.37314-1-imbrenda@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v1,1/1] KVM: s390/mm: Properly reset no-dat | expand |
Sorry, I had copy-pasted the wrong email address for Gerald, fixed now On Thu, 9 Nov 2023 13:36:24 +0100 Claudio Imbrenda <imbrenda@linux.ibm.com> wrote: > When the CMMA state needs to be reset, the no-dat bit also needs to be > reset. Failure to do so could cause issues in the guest, since the > guest expects the bit to be cleared after a reset. > > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > --- > arch/s390/mm/pgtable.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c > index 3bd2ab2a9a34..5cb92941540b 100644 > --- a/arch/s390/mm/pgtable.c > +++ b/arch/s390/mm/pgtable.c > @@ -756,7 +756,7 @@ void ptep_zap_unused(struct mm_struct *mm, unsigned long addr, > pte_clear(mm, addr, ptep); > } > if (reset) > - pgste_val(pgste) &= ~_PGSTE_GPS_USAGE_MASK; > + pgste_val(pgste) &= ~(_PGSTE_GPS_USAGE_MASK | _PGSTE_GPS_NODAT); > pgste_set_unlock(ptep, pgste); > preempt_enable(); > }
Am 09.11.23 um 13:36 schrieb Claudio Imbrenda: > When the CMMA state needs to be reset, the no-dat bit also needs to be > reset. Failure to do so could cause issues in the guest, since the > guest expects the bit to be cleared after a reset. This happens during reset of a guest (or whenever QEMU calls the CLR_CMMA thingi). I think after reset a normal Linux guest has no DAT tables and very likely a cpu reset (with explicit full guest flush) will happen. It will very likely also set the CMMA state during boot before setting up its DAT tables. So for the normal reboot this should be ok. But I can imagine cases that would not be ok. So maybe add cc stable?
Quoting Claudio Imbrenda (2023-11-09 13:36:24) > When the CMMA state needs to be reset, the no-dat bit also needs to be > reset. Failure to do so could cause issues in the guest, since the > guest expects the bit to be cleared after a reset. > > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Please Cc stable and add my: Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 3bd2ab2a9a34..5cb92941540b 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -756,7 +756,7 @@ void ptep_zap_unused(struct mm_struct *mm, unsigned long addr, pte_clear(mm, addr, ptep); } if (reset) - pgste_val(pgste) &= ~_PGSTE_GPS_USAGE_MASK; + pgste_val(pgste) &= ~(_PGSTE_GPS_USAGE_MASK | _PGSTE_GPS_NODAT); pgste_set_unlock(ptep, pgste); preempt_enable(); }
When the CMMA state needs to be reset, the no-dat bit also needs to be reset. Failure to do so could cause issues in the guest, since the guest expects the bit to be cleared after a reset. Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> --- arch/s390/mm/pgtable.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)