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KVM: s390: Fix fault-in code

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Fix the fault-in code so that it does not return success if a
concurrent unmap event invalidated the fault-in process between the
best-effort lockless check and the proper check with lock.

The new behaviour is to retry, like the best-effort lockless check
already did.

This prevents the fault-in handler from returning success without
having actually faulted in the requested page.

Fixes: e907ae5301 ("KVM: s390: Add helper functions for fault handling")
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260602142356.169458-7-imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2026-06-02 16:23:52 +02:00
parent 6af5563e82
commit 9a1dfbbd35
1 changed files with 7 additions and 7 deletions
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14
arch/s390/kvm/faultin.c
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@ -36,7 +36,8 @@ int kvm_s390_faultin_gfn(struct kvm_vcpu *vcpu, struct kvm *kvm, struct guest_fa
struct kvm_s390_mmu_cache *mc = NULL;
struct kvm_memory_slot *slot;
unsigned long inv_seq;
int foll, rc = 0;
int rc = -EAGAIN;
int foll;
foll = f->write_attempt ? FOLL_WRITE : 0;
foll |= f->attempt_pfault ? FOLL_NOWAIT : 0;
@ -53,7 +54,7 @@ int kvm_s390_faultin_gfn(struct kvm_vcpu *vcpu, struct kvm *kvm, struct guest_fa
return 0;
}
while (1) {
while (rc == -EAGAIN) {
f->valid = false;
inv_seq = kvm->mmu_invalidate_seq;
/* Pairs with the smp_wmb() in kvm_mmu_invalidate_end(). */
@ -110,20 +111,19 @@ int kvm_s390_faultin_gfn(struct kvm_vcpu *vcpu, struct kvm *kvm, struct guest_fa
if (!mmu_invalidate_retry_gfn(kvm, inv_seq, f->gfn)) {
f->valid = true;
rc = gmap_link(mc, kvm->arch.gmap, f, slot);
kvm_release_faultin_page(kvm, f->page, !!rc, f->write_attempt);
f->page = NULL;
}
kvm_release_faultin_page(kvm, f->page, !!rc, f->write_attempt);
}
kvm_release_faultin_page(kvm, f->page, true, false);
if (rc == -ENOMEM) {
rc = kvm_s390_mmu_cache_topup(mc);
if (rc)
return rc;
} else if (rc != -EAGAIN) {
return rc;
rc = -EAGAIN;
}
}
return rc;
}
int kvm_s390_get_guest_page(struct kvm *kvm, struct guest_fault *f, gfn_t gfn, bool w)