On 13.12.2017 13:53, Janosch Frank wrote:
> A guest can put DAT tables for a lower level guest in the same huge
> segment as one of its prefixes or a g3 page. This would make it
> necessary for the segment to be unprotected (because of the prefix)
> and protected (because of the shadowing) at the same time. This is not
> possible in this universe.
>
> Hence we split the affected huge segment, so we can protect on a
> per-page basis. Such gmap segments are special and get a new software
> bit, that helps us handling this edge case.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
> ---
> arch/s390/include/asm/gmap.h | 13 ++
> arch/s390/include/asm/pgtable.h | 7 +-
> arch/s390/mm/fault.c | 10 +-
> arch/s390/mm/gmap.c | 256 ++++++++++++++++++++++++++++++++++++----
> arch/s390/mm/pgtable.c | 51 ++++++++
> 5 files changed, 313 insertions(+), 24 deletions(-)
> @@ -1081,20 +1189,27 @@ static int gmap_protect_range(struct gmap *gmap, unsigned long gaddr,
> spinlock_t *ptl;
> unsigned long vmaddr, dist;
> pmd_t *pmdp, *hpmdp;
> - int rc;
> + int rc = 0;
>
> while (len) {
> rc = -EAGAIN;
> vmaddr = __gmap_translate(gmap, gaddr);
> hpmdp = (pmd_t *)huge_pte_offset(gmap->mm, vmaddr, HPAGE_SIZE);
> + if (!hpmdp)
> + BUG();
> /* Do we need tests here? */
> ptl = pmd_lock(gmap->mm, hpmdp);
>
> pmdp = gmap_pmd_op_walk(gmap, gaddr);
> if (pmdp) {
> if (!pmd_large(*pmdp)) {
> - rc = gmap_protect_pte(gmap, gaddr, pmdp, prot,
> - bits);
> + if (gmap_pmd_is_split(pmdp) &&
> + (bits & GMAP_NOTIFY_MPROT)) {
> + pmd_val(*pmdp) |= _SEGMENT_ENTRY_GMAP_IN;
> + }
@David:
This currently breaks my brain. There *was* a reason why I put this
there and I was quite insistent that we needed it. Something about
notification areas on splits, but I absolutely can't remember it. Sigh,
should've made a comment.
This might be a leftover from earlier versions, but could also keep us
from doing mprot notification on pte's.
> +
> + rc = gmap_protect_pte(gmap, gaddr, vmaddr,
> + pmdp, hpmdp, prot, bits);
> if (!rc) {
> len -= PAGE_SIZE;
> gaddr += PAGE_SIZE;
> @@ -1111,7 +1226,9 @@ static int gmap_protect_range(struct gmap *gmap, unsigned long gaddr,
[...]
> @@ -2774,6 +2977,8 @@ void gmap_pmdp_idte_global(struct mm_struct *mm, unsigned long vmaddr)
> IDTE_GLOBAL);
> else
> __pmdp_csp(pmdp);
> +
> + gmap_pmd_split_free(pmdp);
> *entry = _SEGMENT_ENTRY_EMPTY;
> }
> spin_unlock(&gmap->guest_table_lock);
> @@ -2852,6 +3057,7 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long bitmap[4],
> pmd_t *pmdp, *hpmdp;
> spinlock_t *ptl;
>
> + /* Protection against gmap_link vsie unprotection. */
> hpmdp = (pmd_t *)huge_pte_offset(gmap->mm, vmaddr, HPAGE_SIZE);
> if (!hpmdp)
> return;
> @@ -2867,9 +3073,17 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long bitmap[4],
> gaddr, vmaddr))
> memset(bitmap, 0xFF, 32);
s/0xFF/0xff/
Attachment:
signature.asc
Description: OpenPGP digital signature
