* [PATCH v6 1/5] KVM: s390: Fix UCONTROL inconsistencies
2026-11-05 15:37 [PATCH v6 0/5] KVM: s390: Misc bugfixes for 7.4 Claudio Imbrenda
@ 2026-11-05 15:37 ` Claudio Imbrenda
2026-11-05 16:20 ` sashiko-bot
2026-11-05 15:37 ` [PATCH v6 2/5] KVM: s390: Move some skey functions to headers Claudio Imbrenda
` (3 subsequent siblings)
4 siblings, 1 reply; 11+ messages in thread
From: Claudio Imbrenda @ 2026-11-05 15:37 UTC (permalink / raw)
To: kvm; +Cc: linux-s390, borntraeger, frankja, david, nrb, schlameuss, gra
For UCONTROL VMs, when a vCPU segment entry is mapped but unallocated,
the tl field was set to 1. This collides with the present bit, which
means that other parts of gmap would mistake the entry for a present
one.
Refactor the code to use a different combination of flags to indicate a
mapped but unallocated segment.
The new flags combination will result in several functions returning
-EFAULT when used on UCONTROL guests. This is fine, since those
interfaces should not be used for UCONTROL guests to begin with.
Proper fencing of the interfaces that are not allowed for UCONTROL
guests is outside the scope of this patch.
Fixes: a2c17f9270cc ("KVM: s390: New gmap code")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: stable@vger.kernel.org # 7.0+
---
arch/s390/kvm/gmap/dat.h | 22 +++++++++++++++-
arch/s390/kvm/gmap/gmap.c | 54 +++++++++++++++++++--------------------
2 files changed, 47 insertions(+), 29 deletions(-)
diff --git a/arch/s390/kvm/gmap/dat.h b/arch/s390/kvm/gmap/dat.h
index 90389d47ba4e..e6215c0b571f 100644
--- a/arch/s390/kvm/gmap/dat.h
+++ b/arch/s390/kvm/gmap/dat.h
@@ -109,6 +109,8 @@ union pte {
#define _REGION3_FR_MASK (_REGION3_MASK >> PAGE_SHIFT)
#define _PAGES_PER_SEGMENT _PAGE_ENTRIES
#define _PAGES_PER_REGION3 (_PAGES_PER_SEGMENT * _CRST_ENTRIES)
+#define _UCAS_ENTRY_LENGTH 0
+#define _UCAS_ENTRY_OFFSET 3
/* Soft dirty, needed as macro for atomic operations on ptes */
#define _PAGE_SD 0x002
@@ -421,6 +423,23 @@ static inline union crste _crste_fc0(kvm_pfn_t pfn, int tt)
return res;
}
+static inline union crste _crste_ucas(kvm_pfn_t pfn)
+{
+ union crste res = { .val = PFN_PHYS(pfn) };
+
+ res.h.i = 1;
+ res.h.tt = TABLE_TYPE_SEGMENT;
+ /*
+ * Segment entries do not have a TF or TL field; reuse those bits to
+ * indicate that this is a special mappped-but-not-allocated UCAS
+ * entry. Setting TL to 0 ensures that the entry will always be
+ * considered not present.
+ */
+ res.h.fc0.tl = _UCAS_ENTRY_LENGTH;
+ res.h.fc0.tf = _UCAS_ENTRY_OFFSET;
+ return res;
+}
+
/**
* _crste() - Useful constructor for union crste with FC=1
* @pfn: the pfn this pte should point to.
@@ -985,7 +1004,8 @@ static inline int dat_create_slot(struct kvm_s390_mmu_cache *mc, union asce asce
static inline bool crste_is_ucas(union crste crste)
{
- return is_pmd(crste) && crste.h.i && crste.h.fc0.tl == 1 && crste.h.fc == 0;
+ return is_pmd(crste) && crste.h.i && !crste.h.fc &&
+ crste.h.fc0.tl == _UCAS_ENTRY_LENGTH && crste.h.fc0.tf == _UCAS_ENTRY_OFFSET;
}
#endif /* ARCH_KVM_GMAP_DAT_H */
diff --git a/arch/s390/kvm/gmap/gmap.c b/arch/s390/kvm/gmap/gmap.c
index bf91e3d5013b..225fdae3d57c 100644
--- a/arch/s390/kvm/gmap/gmap.c
+++ b/arch/s390/kvm/gmap/gmap.c
@@ -777,16 +777,14 @@ static int gmap_ucas_map_one(struct kvm_s390_mmu_cache *mc, struct gmap *gmap,
if (rc)
return rc;
if (!ptep) {
- newcrste = _crste_fc0(p_gfn, TABLE_TYPE_SEGMENT);
- newcrste.h.i = 1;
- newcrste.h.fc0.tl = 1;
+ newcrste = _crste_ucas(p_gfn);
} else {
pt = pte_table_start(ptep);
dat_set_ptval(pt, PTVAL_VMADDR, p_gfn >> (_SEGMENT_SHIFT - PAGE_SHIFT));
newcrste = _crste_fc0(virt_to_pfn(pt), TABLE_TYPE_SEGMENT);
}
- rc = dat_entry_walk(mc, c_gfn, gmap->asce, DAT_WALK_ALLOC, TABLE_TYPE_SEGMENT,
- &crstep, &ptep);
+ rc = dat_entry_walk(mc, c_gfn, gmap->asce, DAT_WALK_ALLOC | DAT_WALK_IGN_HOLES,
+ TABLE_TYPE_SEGMENT, &crstep, &ptep);
if (rc)
return rc;
do {
@@ -802,8 +800,9 @@ static int gmap_ucas_translate_simple(struct gmap *gmap, gpa_t *gaddr, union crs
union pte *ptep;
int rc;
- rc = dat_entry_walk(NULL, gpa_to_gfn(*gaddr), gmap->asce, DAT_WALK_CONTINUE,
- TABLE_TYPE_SEGMENT, crstepp, &ptep);
+ rc = dat_entry_walk(NULL, gpa_to_gfn(*gaddr), gmap->asce,
+ DAT_WALK_IGN_HOLES | DAT_WALK_ANY,
+ TABLE_TYPE_PAGE_TABLE, crstepp, &ptep);
if (rc || (!ptep && !crste_is_ucas(**crstepp)))
return -EREMOTE;
if (!ptep)
@@ -840,26 +839,24 @@ int gmap_ucas_translate(struct kvm_s390_mmu_cache *mc, struct gmap *gmap, gpa_t
if (rc <= 0)
return rc;
}
- do {
- scoped_guard(write_lock, &gmap->kvm->mmu_lock) {
- rc = gmap_ucas_translate_simple(gmap, gaddr, &crstep);
- if (rc <= 0)
- return rc;
- translated_address = (*gaddr & ~_SEGMENT_MASK) |
- (crstep->val & _SEGMENT_MASK);
- rc = gmap_ucas_map_one(mc, gmap, gpa_to_gfn(translated_address), gfn, true);
- }
- if (!rc) {
- *gaddr = translated_address;
- return 0;
- }
- if (rc != -ENOMEM)
- return -EREMOTE;
- rc = kvm_s390_mmu_cache_topup(mc);
- if (rc)
+ rc = kvm_s390_mmu_cache_topup(mc);
+ if (rc)
+ return rc;
+
+ scoped_guard(write_lock, &gmap->kvm->mmu_lock) {
+ rc = gmap_ucas_translate_simple(gmap, gaddr, &crstep);
+ if (rc <= 0)
return rc;
- } while (1);
- return 0;
+ translated_address = (*gaddr & ~_SEGMENT_MASK) |
+ (crstep->val & _SEGMENT_MASK);
+ rc = gmap_ucas_map_one(mc, gmap, gpa_to_gfn(translated_address), gfn, true);
+ }
+
+ if (!rc)
+ *gaddr = translated_address;
+ if (!rc || rc == -ENOMEM)
+ return rc;
+ return -EREMOTE;
}
int gmap_ucas_map(struct gmap *gmap, gfn_t p_gfn, gfn_t c_gfn, unsigned long count)
@@ -896,8 +893,9 @@ static void gmap_ucas_unmap_one(struct gmap *gmap, gfn_t c_gfn)
union pte *ptep;
int rc;
- rc = dat_entry_walk(NULL, c_gfn, gmap->asce, 0, TABLE_TYPE_SEGMENT, &crstep, &ptep);
- if (rc)
+ rc = dat_entry_walk(NULL, c_gfn, gmap->asce, DAT_WALK_IGN_HOLES,
+ TABLE_TYPE_SEGMENT, &crstep, &ptep);
+ if (rc || !is_pmd(*crstep))
return;
while (!dat_crstep_xchg_atomic(crstep, READ_ONCE(*crstep), _PMD_EMPTY, c_gfn, gmap->asce))
;
--
2.56.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH v6 1/5] KVM: s390: Fix UCONTROL inconsistencies
2026-11-05 15:37 ` [PATCH v6 1/5] KVM: s390: Fix UCONTROL inconsistencies Claudio Imbrenda
@ 2026-11-05 16:20 ` sashiko-bot
0 siblings, 0 replies; 11+ messages in thread
From: sashiko-bot @ 2026-11-05 16:20 UTC (permalink / raw)
To: Claudio Imbrenda, kvm
Cc: linux-s390, Heiko Carstens, Vasily Gorbik, Alexander Gordeev,
Christian Borntraeger
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] KVM: s390: _crste_ucas() collides with crste.tok in _crste_hole()
--
commit a4c739d060e46a8362a876fd2edc730f00fb6503
Author: Claudio Imbrenda <imbrenda@linux.ibm.com>
KVM: s390: Fix UCONTROL inconsistencies
This commit updates how mapped-but-unallocated UCONTROL segment entries
are encoded in union crste so they do not set the tl field to 1 and
collide with the present bit, and adjusts UCAS walks to ignore holes.
> diff --git a/arch/s390/kvm/gmap/dat.h b/arch/s390/kvm/gmap/dat.h
> index 90389d47ba4e0..e6215c0b571f9 100644
> --- a/arch/s390/kvm/gmap/dat.h
> +++ b/arch/s390/kvm/gmap/dat.h
> @@ -109,6 +109,8 @@ union pte {
> #define _REGION3_FR_MASK (_REGION3_MASK >> PAGE_SHIFT)
> #define _PAGES_PER_SEGMENT _PAGE_ENTRIES
> #define _PAGES_PER_REGION3 (_PAGES_PER_SEGMENT * _CRST_ENTRIES)
> +#define _UCAS_ENTRY_LENGTH 0
> +#define _UCAS_ENTRY_OFFSET 3
>
> /* Soft dirty, needed as macro for atomic operations on ptes */
> #define _PAGE_SD 0x002
> @@ -421,6 +423,23 @@ static inline union crste _crste_fc0(kvm_pfn_t pfn, int tt)
> return res;
> }
>
> +static inline union crste _crste_ucas(kvm_pfn_t pfn)
> +{
> + union crste res = { .val = PFN_PHYS(pfn) };
> +
> + res.h.i = 1;
> + res.h.tt = TABLE_TYPE_SEGMENT;
> + /*
> + * Segment entries do not have a TF or TL field; reuse those bits to
> + * indicate that this is a special mappped-but-not-allocated UCAS
> + * entry. Setting TL to 0 ensures that the entry will always be
> + * considered not present.
> + */
> + res.h.fc0.tl = _UCAS_ENTRY_LENGTH;
> + res.h.fc0.tf = _UCAS_ENTRY_OFFSET;
> + return res;
> +}
[Severity: High]
As reported by Sashiko on v5 [1], does _crste_ucas() collide with
crste.tok.type and crste.tok.par when checked by _crste_hole(),
_crste_none(), and dat_entry_walk()?
In union crste, tok.type occupies the top 16 bits (val >> 48) and tok.par
occupies the next 16 bits ((val >> 32) & 0xffff), while h.fc0.tf sits in
the unnamed 26-bit padding of struct tok and setting h.fc0.tl = 0 sets
tok.pr = 0:
arch/s390/kvm/gmap/dat.h:
union {
struct {
unsigned long type :16; /* Token type */
unsigned long par :16; /* Token parameter */
unsigned long :26;
unsigned long i : 1; /* Must be 1 */
unsigned long : 1;
unsigned long tt : 2;
unsigned long : 1;
unsigned long pr : 1; /* Must be 0 */
};
Because _crste_ucas(pfn) stores PFN_PHYS(pfn) in val, crste.tok.type is
(PFN_PHYS(pfn) >> 48) & 0xffff and crste.tok.par is
(PFN_PHYS(pfn) >> 32) & 0xffff.
However, _crste_hole() and _crste_none() do not check crste_is_ucas():
arch/s390/kvm/gmap/dat.h:
static inline bool _crste_hole(union crste crste)
{
return crste.h.i && !crste.tok.pr && crste.tok.type != _DAT_TOKEN_NONE;
}
and dat_entry_walk() checks:
arch/s390/kvm/gmap/dat.c:dat_entry_walk() {
...
if (crste_hole(entry) && !ign_holes)
return entry.tok.type == _DAT_TOKEN_PIC ? entry.tok.par : -EFAULT;
...
if (entry.pmd.h.i && !entry.pmd.h.fc) {
if (!allocate)
return any ? 0 : -ENOENT;
rc = dat_split_ste(mc, &(*last)->pmd, gfn, asce, uses_skeys);
}
When a segment is mapped via KVM_S390_UCAS_MAP (kvm_vm_ioctl_ucas_map() ->
gmap_ucas_map() -> gmap_ucas_map_one()) before the parent segment is
allocated, gmap_ucas_map_one() installs _crste_ucas(p_gfn) into the child
vcpu->arch.gmap->asce. If another gmap function then walks
vcpu->arch.gmap->asce without DAT_WALK_IGN_HOLES:
1. When PFN_PHYS(p_gfn) < (1UL << 48) (i.e. host user address < 256 TiB),
entry.tok.type is 0 (_DAT_TOKEN_NONE), so crste_hole(entry) returns false
instead of failing with -EFAULT. If DAT_WALK_ALLOC is set (for example via
handle_sske() or handle_pfmf() -> dat_cond_set_storage_key(), or via
dat_set_storage_key() or dat_set_cmma_bits()), dat_entry_walk() calls
dat_split_ste() on the UCAS entry in vcpu->arch.gmap->asce. That allocates
a page table in the child gmap (which is leaked on gmap_dispose() because
GMAP_FLAG_OWNS_PAGETABLES is cleared on UCONTROL child gmaps) with zeroed
PGSTEs (PTVAL_VMADDR == 0), causing subsequent gmap_ucas_translate() calls
to translate the segment to GPA 0 in gmap->parent instead of the mapped
user_addr.
2. When (PFN_PHYS(p_gfn) >> 48) == _DAT_TOKEN_PIC (1) (i.e. 256 TiB <=
user_addr < 512 TiB), crste_hole(entry) is true and dat_entry_walk()
returns entry.tok.par ((PFN_PHYS(p_gfn) >> 32) & 0xffff) instead of
-EFAULT. If entry.tok.par is 0, dat_entry_walk() returns 0 with
*ptepp == NULL and *last pointing to the non-leaf UCAS entry, causing
dat_cond_set_storage_key() and dat_set_storage_key() to spin endlessly at
if (!crste_leaf(crste)) goto again; while holding
read_lock(&vcpu->kvm->mmu_lock). If entry.tok.par is non-zero, callers
such as handle_iske(), handle_rrbe(), handle_pfmf(), and
vcpu_check_access_key_gpa() treat those address bits as a guest Program
Interruption Code.
Should _crste_hole(), _crste_none(), and dat_entry_walk() explicitly
handle crste_is_ucas() so unallocated UCAS entries are always treated as
non-PIC holes?
[1] https://lore.kernel.org/r/20261029130044.125032-2-imbrenda@linux.ibm.com
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261105153705.208516-1-imbrenda@linux.ibm.com?part=1
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v6 2/5] KVM: s390: Move some skey functions to headers
2026-11-05 15:37 [PATCH v6 0/5] KVM: s390: Misc bugfixes for 7.4 Claudio Imbrenda
2026-11-05 15:37 ` [PATCH v6 1/5] KVM: s390: Fix UCONTROL inconsistencies Claudio Imbrenda
@ 2026-11-05 15:37 ` Claudio Imbrenda
2026-11-05 16:21 ` sashiko-bot
2026-11-05 15:37 ` [PATCH v6 3/5] KVM: s390: Fix idte_crste() clobber and table type Claudio Imbrenda
` (2 subsequent siblings)
4 siblings, 1 reply; 11+ messages in thread
From: Claudio Imbrenda @ 2026-11-05 15:37 UTC (permalink / raw)
To: kvm; +Cc: linux-s390, borntraeger, frankja, david, nrb, schlameuss, gra
Move some storage key handling functions to headers, since they will be
needed from outside, and they are small, so inlining is acceptable.
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: stable@vger.kernel.org # 7.0+: prerequisite for the next patch
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
arch/s390/kvm/gmap/dat.c | 26 --------------------------
arch/s390/kvm/gmap/dat.h | 26 ++++++++++++++++++++++++++
2 files changed, 26 insertions(+), 26 deletions(-)
diff --git a/arch/s390/kvm/gmap/dat.c b/arch/s390/kvm/gmap/dat.c
index ff80d02c9f56..b9507daaf327 100644
--- a/arch/s390/kvm/gmap/dat.c
+++ b/arch/s390/kvm/gmap/dat.c
@@ -159,32 +159,6 @@ bool __must_check dat_crstep_xchg_atomic(union crste *crstep, union crste old, u
return cspg_crste(crstep, old, new);
}
-static void dat_set_storage_key_from_pgste(union pte pte, union pgste pgste)
-{
- union skey nkey = { .acc = pgste.acc, .fp = pgste.fp };
-
- page_set_storage_key(pte_origin(pte), nkey.skey, 0);
-}
-
-static void dat_move_storage_key(union pte old, union pte new)
-{
- page_set_storage_key(pte_origin(new), page_get_storage_key(pte_origin(old)), 1);
-}
-
-static union pgste dat_save_storage_key_into_pgste(union pte pte, union pgste pgste)
-{
- union skey skey;
-
- skey.skey = page_get_storage_key(pte_origin(pte));
-
- pgste.acc = skey.acc;
- pgste.fp = skey.fp;
- pgste.gr |= skey.r;
- pgste.gc |= skey.c;
-
- return pgste;
-}
-
union pgste __dat_ptep_xchg(union pte *ptep, union pgste pgste, union pte new, gfn_t gfn,
union asce asce, bool uses_skeys)
{
diff --git a/arch/s390/kvm/gmap/dat.h b/arch/s390/kvm/gmap/dat.h
index e6215c0b571f..9cdd1f122d7a 100644
--- a/arch/s390/kvm/gmap/dat.h
+++ b/arch/s390/kvm/gmap/dat.h
@@ -1008,4 +1008,30 @@ static inline bool crste_is_ucas(union crste crste)
crste.h.fc0.tl == _UCAS_ENTRY_LENGTH && crste.h.fc0.tf == _UCAS_ENTRY_OFFSET;
}
+static inline void dat_set_storage_key_from_pgste(union pte pte, union pgste pgste)
+{
+ union skey nkey = { .acc = pgste.acc, .fp = pgste.fp };
+
+ page_set_storage_key(pte_origin(pte), nkey.skey, 0);
+}
+
+static inline void dat_move_storage_key(union pte old, union pte new)
+{
+ page_set_storage_key(pte_origin(new), page_get_storage_key(pte_origin(old)), 1);
+}
+
+static inline union pgste dat_save_storage_key_into_pgste(union pte pte, union pgste pgste)
+{
+ union skey skey;
+
+ skey.skey = page_get_storage_key(pte_origin(pte));
+
+ pgste.acc = skey.acc;
+ pgste.fp = skey.fp;
+ pgste.gr |= skey.r;
+ pgste.gc |= skey.c;
+
+ return pgste;
+}
+
#endif /* ARCH_KVM_GMAP_DAT_H */
--
2.56.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v6 3/5] KVM: s390: Fix idte_crste() clobber and table type
2026-11-05 15:37 [PATCH v6 0/5] KVM: s390: Misc bugfixes for 7.4 Claudio Imbrenda
2026-11-05 15:37 ` [PATCH v6 1/5] KVM: s390: Fix UCONTROL inconsistencies Claudio Imbrenda
2026-11-05 15:37 ` [PATCH v6 2/5] KVM: s390: Move some skey functions to headers Claudio Imbrenda
@ 2026-11-05 15:37 ` Claudio Imbrenda
2026-11-05 16:27 ` sashiko-bot
2026-11-05 15:37 ` [PATCH v6 4/5] KVM: s390: Improve unmapping of large ranges Claudio Imbrenda
2026-11-05 15:37 ` [PATCH v6 5/5] KVM: s390: vsie: Fix pinning using the wrong flag Claudio Imbrenda
4 siblings, 1 reply; 11+ messages in thread
From: Claudio Imbrenda @ 2026-11-05 15:37 UTC (permalink / raw)
To: kvm; +Cc: linux-s390, borntraeger, frankja, david, nrb, schlameuss, gra
Fix idte_crste() to add the missing table-type bits and the missing
"memory" clobber.
Fixes: 5a74e3d93417 ("KVM: s390: KVM-specific bitfields and helper functions")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: stable@vger.kernel.org # 7.0+
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
---
arch/s390/kvm/gmap/dat.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/s390/kvm/gmap/dat.h b/arch/s390/kvm/gmap/dat.h
index 9cdd1f122d7a..79efc56710b7 100644
--- a/arch/s390/kvm/gmap/dat.h
+++ b/arch/s390/kvm/gmap/dat.h
@@ -646,20 +646,22 @@ static __always_inline void idte_crste(union crste *crstep, gfn_t gfn, unsigned
unsigned long table_origin = __pa(crste_table_start(crstep));
unsigned long gaddr = gfn_to_gpa(gfn) & HPAGE_MASK;
+ table_origin |= crstep->val & _REGION_ENTRY_TYPE_MASK;
+
if (__builtin_constant_p(opt) && opt == 0) {
/* flush without guest asce */
asm volatile("idte %[table_origin],0,%[gaddr],%[local]"
: "+m" (*crstep)
: [table_origin] "a" (table_origin), [gaddr] "a" (gaddr),
[local] "i" (local)
- : "cc");
+ : "cc", "memory");
} else {
/* flush with guest asce */
asm volatile("idte %[table_origin],%[asce],%[gaddr_opt],%[local]"
: "+m" (*crstep)
: [table_origin] "a" (table_origin), [gaddr_opt] "a" (gaddr | opt),
[asce] "a" (asce.val), [local] "i" (local)
- : "cc");
+ : "cc", "memory");
}
}
--
2.56.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v6 4/5] KVM: s390: Improve unmapping of large ranges
2026-11-05 15:37 [PATCH v6 0/5] KVM: s390: Misc bugfixes for 7.4 Claudio Imbrenda
` (2 preceding siblings ...)
2026-11-05 15:37 ` [PATCH v6 3/5] KVM: s390: Fix idte_crste() clobber and table type Claudio Imbrenda
@ 2026-11-05 15:37 ` Claudio Imbrenda
2026-11-05 16:42 ` sashiko-bot
2026-11-05 15:37 ` [PATCH v6 5/5] KVM: s390: vsie: Fix pinning using the wrong flag Claudio Imbrenda
4 siblings, 1 reply; 11+ messages in thread
From: Claudio Imbrenda @ 2026-11-05 15:37 UTC (permalink / raw)
To: kvm; +Cc: linux-s390, borntraeger, frankja, david, nrb, schlameuss, gra
When unmapping guest ranges, each individual leaf DAT entry is
invalidated. When unmapping large ranges, this results in a very large
amount of invalidations, which is time consuming. Moreover, since the
unmap callback is called by KVM while holding a spinlock, this also
leads to stall warnings.
Improve the situation by invalidating DAT entries higher in the tree,
instead of each leaf individually.
For small invalidations (up to 1 segment = 1M of guest memory), and
special cases (like protected VMs) regardless of the size, the old and
slow invalidation is performed; all leaf entries are invalidated one by
one.
For large invalidations (larger than 1M of guest memory), the new
strategy is used:
- Invalidate prefixes on the whole range, extending start and end to
1M granularity
- Iterate through the page table pointed to by each pmd and unshadow
entries as needed
- Detach (invalidate) the pmd
- Save storage keys as needed
- Invalidate each (now detached) pte by simply overwriting it
- Reattach the old pmd to point to the updated page table
Fixes: a2c17f9270cc ("KVM: s390: New gmap code")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: stable@vger.kernel.org # 7.0+
Acked-by: Janosch Frank <frankja@linux.ibm.com>
---
arch/s390/kvm/gmap/gmap.c | 136 +++++++++++++++++++++++++++++++++++---
1 file changed, 125 insertions(+), 11 deletions(-)
diff --git a/arch/s390/kvm/gmap/gmap.c b/arch/s390/kvm/gmap/gmap.c
index 225fdae3d57c..b9d92bef5459 100644
--- a/arch/s390/kvm/gmap/gmap.c
+++ b/arch/s390/kvm/gmap/gmap.c
@@ -434,17 +434,8 @@ static long _gmap_unmap_crste(union crste *crstep, gfn_t gfn, gfn_t next, struct
return 0;
}
-/**
- * gmap_unmap_gfn_range() - Unmap a range of guest addresses.
- * @gmap: The gmap to act on.
- * @slot: The memslot in which the range is located.
- * @start: The first gfn to unmap.
- * @end: The gfn after the last one to unmap.
- *
- * Context: Called with the kvm mmu write lock held.
- * Return: false
- */
-bool gmap_unmap_gfn_range(struct gmap *gmap, struct kvm_memory_slot *slot, gfn_t start, gfn_t end)
+static bool gmap_unmap_gfn_range_slow(struct gmap *gmap, struct kvm_memory_slot *slot,
+ gfn_t start, gfn_t end)
{
const struct dat_walk_ops ops = {
.pte_entry = _gmap_unmap_pte,
@@ -462,6 +453,129 @@ bool gmap_unmap_gfn_range(struct gmap *gmap, struct kvm_memory_slot *slot, gfn_t
return false;
}
+static long _gmap_unmap_pud_fast(union crste *crstep, gfn_t gfn, gfn_t next, struct dat_walk *w)
+{
+ union crste old = *crstep;
+
+ /* We only care about large puds */
+ if (!old.h.fc)
+ return 0;
+ /*
+ * The caller did not unmap prefixes outside the original range, which
+ * does not necessarily cover the whole pud.
+ * Since all prefixes are below 2G, the first pud covers them all;
+ * make sure all prefixes are unmapped whenever the first pud is being
+ * unmapped.
+ */
+ if (!gfn)
+ gmap_unmap_prefix(w->priv, 0, next);
+ if (old.s.fc1.vsie_notif)
+ gmap_handle_vsie_unshadow_event(w->priv, gfn);
+
+ if (machine_has_tlb_guest())
+ idte_crste(crstep, gfn, IDTE_GUEST_ASCE, w->asce, 0);
+ else
+ idte_crste(crstep, gfn, 0, w->asce, 0);
+ *crstep = _CRSTE_EMPTY(old.h.tt);
+
+ return 0;
+}
+
+static long _gmap_unmap_pmd_fast(union crste *crstep, gfn_t gfn, gfn_t next, struct dat_walk *w)
+{
+ union crste old = *crstep;
+ struct page_table *pt;
+ gfn_t first, last;
+ unsigned int i;
+
+ if (old.h.fc) {
+ if (old.s.fc1.vsie_notif)
+ gmap_handle_vsie_unshadow_event(w->priv, gfn);
+
+ if (machine_has_tlb_guest())
+ idte_crste(crstep, gfn, IDTE_GUEST_ASCE, w->asce, 0);
+ else
+ idte_crste(crstep, gfn, 0, w->asce, 0);
+ WRITE_ONCE(*crstep, _CRSTE_EMPTY(old.h.tt));
+
+ return 0;
+ }
+
+ if (old.h.i)
+ return 0;
+
+ pt = dereference_pmd(old.pmd);
+ first = max(gfn, w->start) & (PTRS_PER_PTE - 1);
+ last = (min(next, w->end) - 1) & (PTRS_PER_PTE - 1);
+
+ for (i = first; i <= last; i++)
+ if (pte_needs_unshadow(pt->ptes[i], _PTE_EMPTY, pt->pgstes[i]))
+ gmap_handle_vsie_unshadow_event(w->priv, gfn + i);
+
+ /* Detach the page table */
+ if (machine_has_tlb_guest())
+ idte_crste(crstep, gfn, IDTE_GUEST_ASCE, w->asce, 0);
+ else
+ idte_crste(crstep, gfn, 0, w->asce, 0);
+
+ for (i = first; i <= last; i++) {
+ if (pte_hole(pt->ptes[i]))
+ continue;
+ if (!pt->ptes[i].h.i && uses_skeys(w->priv))
+ pt->pgstes[i] = dat_save_storage_key_into_pgste(pt->ptes[i], pt->pgstes[i]);
+ pt->ptes[i] = _PTE_EMPTY;
+ pt->pgstes[i].vsie_notif = 0;
+ pt->pgstes[i].vsie_gmem = 0;
+ pt->pgstes[i].zero = 0;
+ pt->pgstes[i].prefix_notif = 0;
+ }
+
+ barrier();
+ /* Reattach the modified page table */
+ WRITE_ONCE(*crstep, old);
+
+ return 0;
+}
+
+static bool gmap_unmap_gfn_range_fast(struct gmap *gmap, gfn_t start, gfn_t end)
+{
+ const struct dat_walk_ops ops = {
+ .pud_entry = _gmap_unmap_pud_fast,
+ .pmd_entry = _gmap_unmap_pmd_fast,
+ };
+ gfn_t aligned_start = ALIGN_DOWN(start, _PAGE_ENTRIES);
+ gfn_t aligned_end = ALIGN(end, _PAGE_ENTRIES);
+ bool failed;
+
+ lockdep_assert_held_write(&gmap->kvm->mmu_lock);
+
+ /* Prefixes are below 2G; if the start is above 2G, nothing to do */
+ if (aligned_start < _PAGES_PER_REGION3)
+ gmap_unmap_prefix(gmap, aligned_start, aligned_end);
+
+ failed = _dat_walk_gfn_range(start, end, gmap->asce, &ops, DAT_WALK_IGN_HOLES, gmap);
+ KVM_BUG_ON(failed, gmap->kvm);
+ return false;
+}
+
+/**
+ * gmap_unmap_gfn_range() - Unmap a range of guest addresses.
+ * @gmap: The gmap to act on.
+ * @slot: The memslot in which the range is located.
+ * @start: The first gfn to unmap.
+ * @end: The gfn after the last one to unmap.
+ *
+ * Context: Called with the kvm mmu write lock held.
+ * Return: false
+ */
+bool gmap_unmap_gfn_range(struct gmap *gmap, struct kvm_memory_slot *slot, gfn_t start, gfn_t end)
+{
+ if ((end - start <= _PAGES_PER_SEGMENT) ||
+ test_bit(GMAP_FLAG_EXPORT_ON_UNMAP, &gmap->flags) || is_ucontrol(gmap))
+ return gmap_unmap_gfn_range_slow(gmap, slot, start, end);
+ return gmap_unmap_gfn_range_fast(gmap, start, end);
+}
+
static union pgste __pte_test_and_clear_softdirty(union pte *ptep, union pgste pgste, gfn_t gfn,
struct gmap *gmap)
{
--
2.56.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH v6 4/5] KVM: s390: Improve unmapping of large ranges
2026-11-05 15:37 ` [PATCH v6 4/5] KVM: s390: Improve unmapping of large ranges Claudio Imbrenda
@ 2026-11-05 16:42 ` sashiko-bot
0 siblings, 0 replies; 11+ messages in thread
From: sashiko-bot @ 2026-11-05 16:42 UTC (permalink / raw)
To: Claudio Imbrenda
Cc: linux-s390, Heiko Carstens, Vasily Gorbik, Alexander Gordeev,
Christian Borntraeger
> When unmapping guest ranges, each individual leaf DAT entry is
> invalidated. When unmapping large ranges, this results in a very large
> amount of invalidations, which is time consuming. Moreover, since the
> unmap callback is called by KVM while holding a spinlock, this also
> leads to stall warnings.
>
> Improve the situation by invalidating DAT entries higher in the tree,
> instead of each leaf individually.
>
> For small invalidations (up to 1 segment = 1M of guest memory), and
> special cases (like protected VMs) regardless of the size, the old and
> slow invalidation is performed; all leaf entries are invalidated one by
> one.
>
> For large invalidations (larger than 1M of guest memory), the new
> strategy is used:
> - Invalidate prefixes on the whole range, extending start and end to
> 1M granularity
> - Iterate through the page table pointed to by each pmd and unshadow
> entries as needed
> - Detach (invalidate) the pmd
> - Save storage keys as needed
> - Invalidate each (now detached) pte by simply overwriting it
> - Reattach the old pmd to point to the updated page table
>
> Fixes: a2c17f9270cc ("KVM: s390: New gmap code")
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261105153705.208516-1-imbrenda@linux.ibm.com?part=4
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v6 5/5] KVM: s390: vsie: Fix pinning using the wrong flag
2026-11-05 15:37 [PATCH v6 0/5] KVM: s390: Misc bugfixes for 7.4 Claudio Imbrenda
` (3 preceding siblings ...)
2026-11-05 15:37 ` [PATCH v6 4/5] KVM: s390: Improve unmapping of large ranges Claudio Imbrenda
@ 2026-11-05 15:37 ` Claudio Imbrenda
2026-11-05 16:47 ` sashiko-bot
4 siblings, 1 reply; 11+ messages in thread
From: Claudio Imbrenda @ 2026-11-05 15:37 UTC (permalink / raw)
To: kvm; +Cc: linux-s390, borntraeger, frankja, david, nrb, schlameuss, gra
When pinning guest memory using pin_blocks(), gfn_to_page() was used,
which under the hood uses FOLL_GET, which is the wrong type of flag for
memory that is accessed directly by hardware.
Fix by using kvm_vcpu_{,un}map(), which uses FOLL_PIN and is the
correct thing to do.
While technically a bugfix, the previous behaviour can only lead to
guest corruption in extremely convoluted test scenarios that cannot
happen in real/production systems.
Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: stable@vger.kernel.org #7.0+
---
arch/s390/kvm/s390/vsie.c | 133 ++++++++++++++------------------------
1 file changed, 47 insertions(+), 86 deletions(-)
diff --git a/arch/s390/kvm/s390/vsie.c b/arch/s390/kvm/s390/vsie.c
index 5926689fa226..3ce133f20fa2 100644
--- a/arch/s390/kvm/s390/vsie.c
+++ b/arch/s390/kvm/s390/vsie.c
@@ -49,20 +49,21 @@ struct vsie_page {
/* address of the last reported fault to guest2 */
unsigned long fault_addr; /* 0x0228 */
/* calculated guest addresses of satellite control blocks */
- gpa_t sca_gpa; /* 0x0230 */
- gpa_t itdba_gpa; /* 0x0238 */
- gpa_t gvrd_gpa; /* 0x0240 */
- gpa_t riccbd_gpa; /* 0x0248 */
- gpa_t sdnx_gpa; /* 0x0250 */
+ struct kvm_host_map sca_map; /* 0x0230 */
+ struct kvm_host_map itdba_map; /* 0x0260 */
+ struct kvm_host_map gvrd_map; /* 0x0290 */
+ struct kvm_host_map riccbd_map; /* 0x02c0 */
+ struct kvm_host_map sdnx_map; /* 0x02f0 */
+ struct kvm_host_map scb_map; /* 0x0320 */
/*
* guest address of the original SCB. Remains set for free vsie
* pages, so we can properly look them up in our addr_to_page
* radix tree.
*/
- gpa_t scb_gpa; /* 0x0258 */
+ gpa_t scb_gpa; /* 0x0350 */
/* the shadow gmap in use by the vsie_page */
- struct gmap_cache gmap_cache; /* 0x0260 */
- __u8 reserved[0x06f8 - 0x0278]; /* 0x0278 */
+ struct gmap_cache gmap_cache; /* 0x0358 */
+ __u8 reserved[0x06f8 - 0x0370]; /* 0x0370 */
struct kvm_s390_crypto_cb crycb; /* 0x06f8 */
__u8 fac[8 + S390_ARCH_FAC_LIST_SIZE_BYTE];/* 0x07f8 */
};
@@ -681,72 +682,43 @@ static int map_prefix(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page, struct
}
/*
- * Pin the guest page given by gpa and set hpa to the pinned host address.
+ * pin_guest_page() - Pin the given guest page and return its hpa.
+ * @vcpu: the vCPU
+ * @gpa: the gpa to pin
+ * @map: the map representing this pinning.
+ *
* Will always be pinned writable.
*
- * Returns: - 0 on success
- * - -EINVAL if the gpa is not valid guest storage
+ * Returns: - 0 if the gpa is not valid guest storage,
+ * - The host hpa of the pinned page in case of success
*/
-static int pin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t *hpa)
-{
- struct page *page;
-
- page = gfn_to_page(kvm, gpa_to_gfn(gpa));
- if (!page)
- return -EINVAL;
- *hpa = (hpa_t)page_to_phys(page) + (gpa & ~PAGE_MASK);
- return 0;
-}
-
-/* Unpins a page previously pinned via pin_guest_page, marking it as dirty. */
-static void unpin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t hpa)
+static hpa_t pin_guest_page(struct kvm_vcpu *vcpu, gpa_t gpa, struct kvm_host_map *map)
{
- kvm_release_page_dirty(pfn_to_page(phys_to_pfn(hpa)));
- /* mark the page always as dirty for migration */
- mark_page_dirty(kvm, gpa_to_gfn(gpa));
+ if (kvm_vcpu_map(vcpu, gpa_to_gfn(gpa), map))
+ return 0;
+ return (hpa_t)PFN_PHYS(map->pfn) + (gpa & ~PAGE_MASK);
}
/* unpin all blocks previously pinned by pin_blocks(), marking them dirty */
static void unpin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
{
struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
- hpa_t hpa;
- hpa = (u64) scb_s->scaoh << 32 | scb_s->scaol;
- if (hpa) {
- unpin_guest_page(vcpu->kvm, vsie_page->sca_gpa, hpa);
- vsie_page->sca_gpa = 0;
- scb_s->scaol = 0;
- scb_s->scaoh = 0;
- }
+ kvm_vcpu_unmap(vcpu, &vsie_page->sca_map);
+ scb_s->scaol = 0;
+ scb_s->scaoh = 0;
- hpa = scb_s->itdba;
- if (hpa) {
- unpin_guest_page(vcpu->kvm, vsie_page->itdba_gpa, hpa);
- vsie_page->itdba_gpa = 0;
- scb_s->itdba = 0;
- }
+ kvm_vcpu_unmap(vcpu, &vsie_page->itdba_map);
+ scb_s->itdba = 0;
- hpa = scb_s->gvrd;
- if (hpa) {
- unpin_guest_page(vcpu->kvm, vsie_page->gvrd_gpa, hpa);
- vsie_page->gvrd_gpa = 0;
- scb_s->gvrd = 0;
- }
+ kvm_vcpu_unmap(vcpu, &vsie_page->gvrd_map);
+ scb_s->gvrd = 0;
- hpa = scb_s->riccbd;
- if (hpa) {
- unpin_guest_page(vcpu->kvm, vsie_page->riccbd_gpa, hpa);
- vsie_page->riccbd_gpa = 0;
- scb_s->riccbd = 0;
- }
+ kvm_vcpu_unmap(vcpu, &vsie_page->riccbd_map);
+ scb_s->riccbd = 0;
- hpa = scb_s->sdnxo;
- if (hpa) {
- unpin_guest_page(vcpu->kvm, vsie_page->sdnx_gpa, hpa);
- vsie_page->sdnx_gpa = 0;
- scb_s->sdnxo = 0;
- }
+ kvm_vcpu_unmap(vcpu, &vsie_page->sdnx_map);
+ scb_s->sdnxo = 0;
}
/*
@@ -783,13 +755,12 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
((gpa + offsetof(struct bsca_block, cpu[0]) - 1) & PAGE_MASK))
rc = set_validity_icpt(scb_s, 0x003bU);
if (!rc) {
- rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
- if (rc)
+ hpa = pin_guest_page(vcpu, gpa, &vsie_page->sca_map);
+ if (!hpa)
rc = set_validity_icpt(scb_s, 0x0034U);
}
if (rc)
goto unpin;
- vsie_page->sca_gpa = gpa;
scb_s->scaoh = (u32)((u64)hpa >> 32);
scb_s->scaol = (u32)(u64)hpa;
}
@@ -801,12 +772,11 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
goto unpin;
}
/* 256 bytes cannot cross page boundaries */
- rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
- if (rc) {
+ hpa = pin_guest_page(vcpu, gpa, &vsie_page->itdba_map);
+ if (!hpa) {
rc = set_validity_icpt(scb_s, 0x0080U);
goto unpin;
}
- vsie_page->itdba_gpa = gpa;
scb_s->itdba = hpa;
}
@@ -820,12 +790,11 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
* 512 bytes vector registers cannot cross page boundaries
* if this block gets bigger, we have to shadow it.
*/
- rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
- if (rc) {
+ hpa = pin_guest_page(vcpu, gpa, &vsie_page->gvrd_map);
+ if (!hpa) {
rc = set_validity_icpt(scb_s, 0x1310U);
goto unpin;
}
- vsie_page->gvrd_gpa = gpa;
scb_s->gvrd = hpa;
}
@@ -836,13 +805,12 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
goto unpin;
}
/* 64 bytes cannot cross page boundaries */
- rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
- if (rc) {
+ hpa = pin_guest_page(vcpu, gpa, &vsie_page->riccbd_map);
+ if (!hpa) {
rc = set_validity_icpt(scb_s, 0x0043U);
goto unpin;
}
/* Validity 0x0044 will be checked by SIE */
- vsie_page->riccbd_gpa = gpa;
scb_s->riccbd = hpa;
}
if (((scb_s->ecb & ECB_GS) && !(scb_s->ecd & ECD_HOSTREGMGMT)) ||
@@ -866,12 +834,11 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
/* Due to alignment rules (checked above) this cannot
* cross page boundaries
*/
- rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
- if (rc) {
+ hpa = pin_guest_page(vcpu, gpa, &vsie_page->sdnx_map);
+ if (!hpa) {
rc = set_validity_icpt(scb_s, 0x10b0U);
goto unpin;
}
- vsie_page->sdnx_gpa = gpa;
scb_s->sdnxo = hpa | sdnxc;
}
return 0;
@@ -881,13 +848,9 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
}
/* unpin the scb provided by guest 2, marking it as dirty */
-static void unpin_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
- gpa_t gpa)
+static void unpin_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
{
- hpa_t hpa = virt_to_phys(vsie_page->scb_o);
-
- if (hpa)
- unpin_guest_page(vcpu->kvm, gpa, hpa);
+ kvm_vcpu_unmap(vcpu, &vsie_page->scb_map);
vsie_page->scb_o = NULL;
}
@@ -901,12 +864,10 @@ static int pin_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
gpa_t gpa)
{
hpa_t hpa;
- int rc;
- rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
- if (rc) {
- rc = kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
- WARN_ON_ONCE(rc);
+ hpa = pin_guest_page(vcpu, gpa, &vsie_page->scb_map);
+ if (!hpa) {
+ WARN_ON_ONCE(kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING));
return 1;
}
vsie_page->scb_o = phys_to_virt(hpa);
@@ -1601,7 +1562,7 @@ int kvm_s390_handle_vsie(struct kvm_vcpu *vcpu)
out_unshadow:
unshadow_scb(vcpu, vsie_page);
out_unpin_scb:
- unpin_scb(vcpu, vsie_page, scb_addr);
+ unpin_scb(vcpu, vsie_page);
out_put:
put_vsie_page(vsie_page);
--
2.56.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH v6 5/5] KVM: s390: vsie: Fix pinning using the wrong flag
2026-11-05 15:37 ` [PATCH v6 5/5] KVM: s390: vsie: Fix pinning using the wrong flag Claudio Imbrenda
@ 2026-11-05 16:47 ` sashiko-bot
0 siblings, 0 replies; 11+ messages in thread
From: sashiko-bot @ 2026-11-05 16:47 UTC (permalink / raw)
To: Claudio Imbrenda
Cc: linux-s390, Heiko Carstens, Vasily Gorbik, Alexander Gordeev,
Christian Borntraeger
> When pinning guest memory using pin_blocks(), gfn_to_page() was used,
> which under the hood uses FOLL_GET, which is the wrong type of flag for
> memory that is accessed directly by hardware.
>
> Fix by using kvm_vcpu_{,un}map(), which uses FOLL_PIN and is the
> correct thing to do.
>
> While technically a bugfix, the previous behaviour can only lead to
> guest corruption in extremely convoluted test scenarios that cannot
> happen in real/production systems.
>
> Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261105153705.208516-1-imbrenda@linux.ibm.com?part=5
^ permalink raw reply [flat|nested] 11+ messages in thread