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KVM: s390: Fix a deadlock

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In some scenarios, a deadlock can happen, involving _do_shadow_pte().

Convert all usages of pgste_get_lock() to pgste_get_trylock() in
_do_shadow_pte() and return -EAGAIN. All callers can already deal with
-EAGAIN being returned.

Fixes: e38c884df9 ("KVM: s390: Switch to new gmap")
Tested-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2026-03-03 18:52:06 +01:00
parent 5ee8dbf546
commit f303406efd
1 changed files with 4 additions and 2 deletions
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6
arch/s390/kvm/gaccess.c
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@ -1434,7 +1434,8 @@ static int _do_shadow_pte(struct gmap *sg, gpa_t raddr, union pte *ptep_h, union
if (rc)
return rc;
pgste = pgste_get_lock(ptep_h);
if (!pgste_get_trylock(ptep_h, &pgste))
return -EAGAIN;
newpte = _pte(f->pfn, f->writable, !p, 0);
newpte.s.d |= ptep->s.d;
newpte.s.sd |= ptep->s.sd;
@ -1444,7 +1445,8 @@ static int _do_shadow_pte(struct gmap *sg, gpa_t raddr, union pte *ptep_h, union
pgste_set_unlock(ptep_h, pgste);
newpte = _pte(f->pfn, 0, !p, 0);
pgste = pgste_get_lock(ptep);
if (!pgste_get_trylock(ptep, &pgste))
return -EAGAIN;
pgste = __dat_ptep_xchg(ptep, pgste, newpte, gpa_to_gfn(raddr), sg->asce, uses_skeys(sg));
pgste_set_unlock(ptep, pgste);