Re: [RFC/PATCH 02/22] s390/mm: Abstract gmap notify bit setting

David Hildenbrand
2017-11-10T12:57:16Z

On 06.11.2017 23:29, Janosch Frank wrote:
> Currently we use the software PGSTE bits PGSTE_IN_BIT and PGSTE_VSIE_BIT
> to notify before an invalidation occurs on a prefix page or a VSIE page
> respectively. Both bits only work for a PGSTE, which only exists for
> page tables.
>
> For huge page support we also need such bits for segments (pmds) so
> let's introduce abstract GMAP_ENTRY_* bits that will be realized into
> the respective bits when gmap DAT table entries are protected.
>
> Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> arch/s390/include/asm/gmap.h | 4 ++++
> arch/s390/mm/gmap.c | 13 ++++++++-----
> 2 files changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
> index 741ddba..f3d84a8 100644
> --- a/arch/s390/include/asm/gmap.h
> +++ b/arch/s390/include/asm/gmap.h
> @@ -8,6 +8,10 @@
> #ifndef _ASM_S390_GMAP_H
> #define _ASM_S390_GMAP_H
>
> +/* Generic bits for GMAP notification on DAT table entry changes. */
> +#define GMAP_ENTRY_VSIE 0x2
> +#define GMAP_ENTRY_IN 0x1

Can we rename
GMAP_ENTRY_VSIE -> GMAP_ENTRY_SHADOW_IN

and also

PGSTE_VSIE_BIT -> PGSTE_SHADOW_IN_BIT

as they are used for managing shadow page table invalidation.

Also, a better fitting name for ENTRY would be nice :)
(GMAP_NOTIFY_...)

> +
> /**
> * struct gmap_struct - guest address space
> * @list: list head for the mm->context gmap list
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 9757242..74e2062 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -927,7 +927,7 @@ static inline void gmap_pmd_op_end(struct gmap *gmap, pmd_t *pmdp)
> * @gaddr: virtual address in the guest address space
> * @pmdp: pointer to the pmd associated with the pte
> * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
> - * @bits: pgste notification bits to set
> + * @bits: notification bits to set
> *
> * Returns 0 if successfully protected, -ENOMEM if out of memory and
> * -EAGAIN if a fixup is needed.
> @@ -941,6 +941,7 @@ static int gmap_protect_pte(struct gmap *gmap, unsigned long gaddr,
> int rc;
> pte_t *ptep;
> spinlock_t *ptl = NULL;
> + unsigned long pbits = 0;
>
> /* We have no upper segment, let's go back and fix this up. */
> if (pmd_val(*pmdp) & _SEGMENT_ENTRY_INVALID)
> @@ -954,8 +955,10 @@ static int gmap_protect_pte(struct gmap *gmap, unsigned long gaddr,
> return -ENOMEM;
> }
>
> + pbits |= (bits & GMAP_ENTRY_IN) ? PGSTE_IN_BIT : 0;
> + pbits |= (bits & GMAP_ENTRY_VSIE) ? PGSTE_VSIE_BIT : 0;
> /* Protect and unlock. */
> - rc = ptep_force_prot(gmap->mm, gaddr, ptep, prot, bits);
> + rc = ptep_force_prot(gmap->mm, gaddr, ptep, prot, pbits);
> if (ptl)
> gmap_pte_op_end(ptl);
> return rc;
> @@ -1031,7 +1034,7 @@ int gmap_mprotect_notify(struct gmap *gmap, unsigned long gaddr,
> if (!MACHINE_HAS_ESOP && prot == PROT_READ)
> return -EINVAL;
> down_read(&gmap->mm->mmap_sem);
> - rc = gmap_protect_range(gmap, gaddr, len, prot, PGSTE_IN_BIT);
> + rc = gmap_protect_range(gmap, gaddr, len, prot, GMAP_ENTRY_IN);
> up_read(&gmap->mm->mmap_sem);
> return rc;
> }
> @@ -1153,7 +1156,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
> if (ptep) {
> spin_lock(&sg->guest_table_lock);
> rc = ptep_force_prot(parent->mm, paddr, ptep, prot,
> - PGSTE_VSIE_BIT);
> + GMAP_ENTRY_VSIE);
> if (!rc)
> gmap_insert_rmap(sg, vmaddr, rmap);
> spin_unlock(&sg->guest_table_lock);
> @@ -1622,7 +1625,7 @@ struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce,
> down_read(&parent->mm->mmap_sem);
> rc = gmap_protect_range(parent, asce & _ASCE_ORIGIN,
> ((asce & _ASCE_TABLE_LENGTH) + 1) * PAGE_SIZE,
> - PROT_READ, PGSTE_VSIE_BIT);
> + PROT_READ, GMAP_ENTRY_VSIE);
> up_read(&parent->mm->mmap_sem);
> spin_lock(&parent->shadow_lock);
> new->initialized = true;
>

Makes sense.

--

Thanks,

David / dhildenb