Commit 0f2b760a authored by Claudio Imbrenda's avatar Claudio Imbrenda
Browse files

KVM: s390: Correctly handle guest mappings without struct page 



Introduce a new special softbit for large pages, like already presend
for normal pages, and use it to mark guest mappings that do not have
struct pages.

Whenever a leaf DAT entry becomes dirty, check the special softbit and
only call SetPageDirty() if there is an actual struct page.

Move the logic to mark pages dirty inside _gmap_ptep_xchg() and
_gmap_crstep_xchg_atomic(), to avoid needlessly duplicating the code.

Fixes: 5a74e3d9 ("KVM: s390: KVM-specific bitfields and helper functions")
Fixes: a2c17f92 ("KVM: s390: New gmap code")
Reviewed-by: default avatarChristian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
parent 45921d02

arch/s390/kvm/dat.h

+6 −6
Original line number Diff line number Diff line
@@ -160,14 +160,14 @@ union pmd { 
			unsigned long              :44; /* HW */

			unsigned long              : 3; /* Unused */

			unsigned long              : 1; /* HW */

			unsigned long s            : 1; /* Special */

			unsigned long w            : 1; /* Writable soft-bit */

			unsigned long r            : 1; /* Readable soft-bit */

			unsigned long d            : 1; /* Dirty */

			unsigned long y            : 1; /* Young */

			unsigned long prefix_notif : 1; /* Guest prefix invalidation notification */

			unsigned long              : 3; /* HW */

			unsigned long prefix_notif : 1; /* Guest prefix invalidation notification */

			unsigned long vsie_notif   : 1; /* Referenced in a shadow table */

			unsigned long              : 1; /* Unused */

			unsigned long              : 4; /* HW */

			unsigned long sd           : 1; /* Soft-Dirty */

			unsigned long pr           : 1; /* Present */
@@ -183,14 +183,14 @@ union pud { 
			unsigned long              :33; /* HW */

			unsigned long              :14; /* Unused */

			unsigned long              : 1; /* HW */

			unsigned long s            : 1; /* Special */

			unsigned long w            : 1; /* Writable soft-bit */

			unsigned long r            : 1; /* Readable soft-bit */

			unsigned long d            : 1; /* Dirty */

			unsigned long y            : 1; /* Young */

			unsigned long prefix_notif : 1; /* Guest prefix invalidation notification */

			unsigned long              : 3; /* HW */

			unsigned long prefix_notif : 1; /* Guest prefix invalidation notification */

			unsigned long vsie_notif   : 1; /* Referenced in a shadow table */

			unsigned long              : 1; /* Unused */

			unsigned long              : 4; /* HW */

			unsigned long sd           : 1; /* Soft-Dirty */

			unsigned long pr           : 1; /* Present */
@@ -254,14 +254,14 @@ union crste { 
		struct {

			unsigned long              :47;

			unsigned long              : 1; /* HW (should be 0) */

			unsigned long s            : 1; /* Special */

			unsigned long w            : 1; /* Writable */

			unsigned long r            : 1; /* Readable */

			unsigned long d            : 1; /* Dirty */

			unsigned long y            : 1; /* Young */

			unsigned long prefix_notif : 1; /* Guest prefix invalidation notification */

			unsigned long              : 3; /* HW */

			unsigned long prefix_notif : 1; /* Guest prefix invalidation notification */

			unsigned long vsie_notif   : 1; /* Referenced in a shadow table */

			unsigned long              : 1;

			unsigned long              : 4; /* HW */

			unsigned long sd           : 1; /* Soft-Dirty */

			unsigned long pr           : 1; /* Present */

arch/s390/kvm/gmap.c

+4 −7
Original line number Diff line number Diff line
@@ -519,7 +519,7 @@ void gmap_sync_dirty_log(struct gmap *gmap, gfn_t start, gfn_t end) 
	_dat_walk_gfn_range(start, end, gmap->asce, &walk_ops, 0, gmap);

}



static int gmap_handle_minor_crste_fault(union asce asce, struct guest_fault *f)

static int gmap_handle_minor_crste_fault(struct gmap *gmap, struct guest_fault *f)

{

	union crste newcrste, oldcrste = READ_ONCE(*f->crstep);
@@ -544,10 +544,8 @@ static int gmap_handle_minor_crste_fault(union asce asce, struct guest_fault *f) 
			newcrste.s.fc1.d = 1;

			newcrste.s.fc1.sd = 1;

		}

		if (!oldcrste.s.fc1.d && newcrste.s.fc1.d)

			SetPageDirty(phys_to_page(crste_origin_large(newcrste)));

		/* In case of races, let the slow path deal with it. */

		return !dat_crstep_xchg_atomic(f->crstep, oldcrste, newcrste, f->gfn, asce);

		return !gmap_crstep_xchg_atomic(gmap, f->crstep, oldcrste, newcrste, f->gfn);

	}

	/* Trying to write on a read-only page, let the slow path deal with it. */

	return 1;
@@ -576,8 +574,6 @@ static int _gmap_handle_minor_pte_fault(struct gmap *gmap, union pgste *pgste, 
		newpte.s.d = 1;

		newpte.s.sd = 1;

	}

	if (!oldpte.s.d && newpte.s.d)

		SetPageDirty(pfn_to_page(newpte.h.pfra));

	*pgste = gmap_ptep_xchg(gmap, f->ptep, newpte, *pgste, f->gfn);



	return 0;
@@ -614,7 +610,7 @@ int gmap_try_fixup_minor(struct gmap *gmap, struct guest_fault *fault) 
			fault->callback(fault);

		pgste_set_unlock(fault->ptep, pgste);

	} else {

		rc = gmap_handle_minor_crste_fault(gmap->asce, fault);

		rc = gmap_handle_minor_crste_fault(gmap, fault);

		if (!rc && fault->callback)

			fault->callback(fault);

	}
@@ -669,6 +665,7 @@ static int _gmap_link(struct kvm_s390_mmu_cache *mc, struct gmap *gmap, int leve 
			oldval = READ_ONCE(*f->crstep);

			newval = _crste_fc1(f->pfn, oldval.h.tt, f->writable,

					    f->write_attempt | oldval.s.fc1.d);

			newval.s.fc1.s = !f->page;

			newval.s.fc1.sd = oldval.s.fc1.sd;

			if (oldval.val != _CRSTE_EMPTY(oldval.h.tt).val &&

			    crste_origin_large(oldval) != crste_origin_large(newval))

arch/s390/kvm/gmap.h

+4 −0
Original line number Diff line number Diff line
@@ -185,6 +185,8 @@ static inline union pgste _gmap_ptep_xchg(struct gmap *gmap, union pte *ptep, un 
		else

			_gmap_handle_vsie_unshadow_event(gmap, gfn);

	}

	if (!ptep->s.d && newpte.s.d && !newpte.s.s)

		SetPageDirty(pfn_to_page(newpte.h.pfra));

	return __dat_ptep_xchg(ptep, pgste, newpte, gfn, gmap->asce, uses_skeys(gmap));

}
@@ -220,6 +222,8 @@ static inline bool __must_check _gmap_crstep_xchg_atomic(struct gmap *gmap, unio 
		else

			_gmap_handle_vsie_unshadow_event(gmap, gfn);

	}

	if (!oldcrste.s.fc1.d && newcrste.s.fc1.d && !newcrste.s.fc1.s)

		SetPageDirty(phys_to_page(crste_origin_large(newcrste)));

	return dat_crstep_xchg_atomic(crstep, oldcrste, newcrste, gfn, gmap->asce);

}