Commit 3ffe5eb4 authored by Claudio Imbrenda's avatar Claudio Imbrenda
Browse files

KVM: s390: vsie: Fix races with partial gmap invalidations 



Introduce a new boolean flag, used for shadow gmaps, to keep track of
whether the gmap has been invalidated, either partially or totally.

Use the new flag to check whether shadow gmap invalidations happened
during shadowing. In such cases, abort whatever was going on, return
-EAGAIN and let the caller try again.

Fixes: 19d6c5b8 ("KVM: s390: vsie: Fix unshadowing while shadowing")
Signed-off-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260407161721.247044-1-imbrenda@linux.ibm.com>
parent bfe62a45

arch/s390/kvm/gaccess.c

+5 −4
Original line number Diff line number Diff line
@@ -1449,7 +1449,7 @@ static int _do_shadow_pte(struct gmap *sg, gpa_t raddr, union pte *ptep_h, union 
	pgste_set_unlock(ptep_h, pgste);

	if (rc)

		return rc;

	if (!sg->parent)

	if (sg->invalidated)

		return -EAGAIN;



	newpte = _pte(f->pfn, 0, !p, 0);
@@ -1479,7 +1479,7 @@ static int _do_shadow_crste(struct gmap *sg, gpa_t raddr, union crste *host, uni 


	do {

		/* _gmap_crstep_xchg_atomic() could have unshadowed this shadow gmap */

		if (!sg->parent)

		if (sg->invalidated)

			return -EAGAIN;

		oldcrste = READ_ONCE(*host);

		newcrste = _crste_fc1(f->pfn, oldcrste.h.tt, f->writable, !p);
@@ -1492,7 +1492,7 @@ static int _do_shadow_crste(struct gmap *sg, gpa_t raddr, union crste *host, uni 
		if (!newcrste.h.p && !f->writable)

			return -EOPNOTSUPP;

	} while (!_gmap_crstep_xchg_atomic(sg->parent, host, oldcrste, newcrste, f->gfn, false));

	if (!sg->parent)

	if (sg->invalidated)

		return -EAGAIN;



	newcrste = _crste_fc1(f->pfn, oldcrste.h.tt, 0, !p);
@@ -1545,7 +1545,7 @@ static int _gaccess_do_shadow(struct kvm_s390_mmu_cache *mc, struct gmap *sg, 
				       entries[i].pfn, i + 1, entries[i].writable);

		if (rc)

			return rc;

		if (!sg->parent)

		if (sg->invalidated)

			return -EAGAIN;

	}
@@ -1601,6 +1601,7 @@ static inline int _gaccess_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg, 
		scoped_guard(spinlock, &parent->children_lock) {

			if (READ_ONCE(sg->parent) != parent)

				return -EAGAIN;

			sg->invalidated = false;

			rc = _gaccess_do_shadow(vcpu->arch.mc, sg, saddr, walk);

		}

		if (rc == -ENOMEM)

arch/s390/kvm/gmap.c

+3 −0
Original line number Diff line number Diff line
@@ -181,6 +181,7 @@ void gmap_remove_child(struct gmap *child) 


	list_del(&child->list);

	child->parent = NULL;

	child->invalidated = true;

}



/**
@@ -1069,6 +1070,7 @@ static void gmap_unshadow_level(struct gmap *sg, gfn_t r_gfn, int level) 
	if (level > TABLE_TYPE_PAGE_TABLE)

		align = 1UL << (11 * level + _SEGMENT_SHIFT);

	kvm_s390_vsie_gmap_notifier(sg, ALIGN_DOWN(gaddr, align), ALIGN(gaddr + 1, align));

	sg->invalidated = true;

	if (dat_entry_walk(NULL, r_gfn, sg->asce, 0, level, &crstep, &ptep))

		return;

	if (ptep) {
@@ -1174,6 +1176,7 @@ static inline int __gmap_protect_asce_top_level(struct kvm_s390_mmu_cache *mc, s 
	scoped_guard(spinlock, &parent->children_lock) {

		if (READ_ONCE(sg->parent) != parent)

			return -EAGAIN;

		sg->invalidated = false;

		for (i = 0; i < CRST_TABLE_PAGES; i++) {

			if (!context->f[i].valid)

				continue;

arch/s390/kvm/gmap.h

+1 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ enum gmap_flags { 
struct gmap {

	unsigned long flags;

	unsigned char edat_level;

	bool invalidated;

	struct kvm *kvm;

	union asce asce;

	struct list_head list;