[PATCH v4 01/11] KVM: arm/arm64: vgic-its: fix return value for device table restore

Eric Auger
2017-10-17T07:10:32Z

AT the moment if ITT only contains invalid entries,
vgic_its_restore_itt returns 1 and this is considered as
an an error in vgic_its_restore_dte.

Also in case the device table only contains invalid entries,
the table restore fails and this is not correct.

This patch fully revisits the errror handling while fixing those
2 bugs.

- entry_fn_t now takes a valid output paraleter
- scan_its_table() now returns <= 0 values and output 2 booleans,
valid and last.
- vgic_its_restore_itt() now returns <= 0 values.
- vgic_its_restore_device_tables() also returns <= 0 values.

With that patch we are able to properly handle the case where
all data are invalid but we still are able to detect the case
where a next entry was referenced by some valid entry and
never found.

Fixes: 57a9a117154c93 (KVM: arm64: vgic-its: Device table save/restore)
Fixes: eff484e0298da5 (KVM: arm64: vgic-its: ITT save and restore)
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: wanghaibin <wanghaibin.wang@huawei.com>

---

need to CC stable

v3 -> v4:
- set *valid at beginning of handle_l1_dte

v2 -> v3:
- add comments
- added valid parameter
- vgic_its_restore_itt don't return +1 anymore
- reword the commit message

v1 -> v2:
- if (ret > 0) ret = 0
---
virt/kvm/arm/vgic/vgic-its.c | 95 ++++++++++++++++++++++++++++++++------------
1 file changed, 70 insertions(+), 25 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index f51c1e1..eea14a1 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -1772,16 +1772,20 @@ static u32 compute_next_eventid_offset(struct list_head *h, struct its_ite *ite)

/**
* entry_fn_t - Callback called on a table entry restore path
+ *
* @its: its handle
* @id: id of the entry
* @entry: pointer to the entry
* @opaque: pointer to an opaque data
+ * @valid: indicates whether valid data is associated to this entry
+ * (the entry itself in case of linear table or entries in the next level,
+ * in case of hierachical tables)
*
* Return: < 0 on error, 0 if last element was identified, id offset to next
* element otherwise
*/
typedef int (*entry_fn_t)(struct vgic_its *its, u32 id, void *entry,
- void *opaque);
+ void *opaque, bool *valid);

/**
* scan_its_table - Scan a contiguous table in guest RAM and applies a function
@@ -1794,29 +1798,34 @@ typedef int (*entry_fn_t)(struct vgic_its *its, u32 id, void *entry,
* @start_id: the ID of the first entry in the table
* (non zero for 2d level tables)
* @fn: function to apply on each entry
+ * @opaque: opaque data passed to @fn
+ * @valid: indicates whether the table contains any valid data
+ * @last: returns whether the last valid entry was decoded
*
- * Return: < 0 on error, 0 if last element was identified, 1 otherwise
- * (the last element may not be found on second level tables)
+ * Return: < 0 on error, 0 on success
*/
static int scan_its_table(struct vgic_its *its, gpa_t base, int size, int esz,
- int start_id, entry_fn_t fn, void *opaque)
+ int start_id, entry_fn_t fn, void *opaque,
+ bool *valid, bool *last)
{
void *entry = kzalloc(esz, GFP_KERNEL);
struct kvm *kvm = its->dev->kvm;
unsigned long len = size;
int id = start_id;
gpa_t gpa = base;
+ int next_offset = 0;
int ret;

while (len > 0) {
- int next_offset;
size_t byte_offset;
+ bool entry_valid;

ret = kvm_read_guest(kvm, gpa, entry, esz);
if (ret)
goto out;

- next_offset = fn(its, id, entry, opaque);
+ next_offset = fn(its, id, entry, opaque, &entry_valid);
+ *valid |= entry_valid;
if (next_offset <= 0) {
ret = next_offset;
goto out;
@@ -1827,9 +1836,15 @@ static int scan_its_table(struct vgic_its *its, gpa_t base, int size, int esz,
gpa += byte_offset;
len -= byte_offset;
}
- ret = 1;
-
+ /*
+ * the table lookup was completed without identifying the
+ * last valid entry (ie. next_offset > 0).
+ */
+ ret = 0;
out:
+ if (!next_offset)
+ *last = true;
+
kfree(entry);
return ret;
}
@@ -1854,12 +1869,14 @@ static int vgic_its_save_ite(struct vgic_its *its, struct its_device *dev,

/**
* vgic_its_restore_ite - restore an interrupt translation entry
+ *
* @event_id: id used for indexing
* @ptr: pointer to the ITE entry
* @opaque: pointer to the its_device
+ * @valid: indicates whether the ite is valid
*/
static int vgic_its_restore_ite(struct vgic_its *its, u32 event_id,
- void *ptr, void *opaque)
+ void *ptr, void *opaque, bool *valid)
{
struct its_device *dev = (struct its_device *)opaque;
struct its_collection *collection;
@@ -1879,7 +1896,9 @@ static int vgic_its_restore_ite(struct vgic_its *its, u32 event_id,
coll_id = val & KVM_ITS_ITE_ICID_MASK;
lpi_id = (val & KVM_ITS_ITE_PINTID_MASK) >> KVM_ITS_ITE_PINTID_SHIFT;

- if (!lpi_id)
+ *valid = !!lpi_id;
+
+ if (!*valid)
return 1; /* invalid entry, no choice but to scan next entry */

if (lpi_id < VGIC_MIN_LPI)
@@ -1940,6 +1959,14 @@ static int vgic_its_save_itt(struct vgic_its *its, struct its_device *device)
return 0;
}

+/**
+ * vgic_its_restore_itt - restore the ITT of a device
+ *
+ * @its: its handle
+ * @dev: device handle
+ *
+ * Return 0 on success, < 0 on error
+ */
static int vgic_its_restore_itt(struct vgic_its *its, struct its_device *dev)
{
const struct vgic_its_abi *abi = vgic_its_get_abi(its);
@@ -1947,9 +1974,15 @@ static int vgic_its_restore_itt(struct vgic_its *its, struct its_device *dev)
int ret;
int ite_esz = abi->ite_esz;
size_t max_size = BIT_ULL(dev->num_eventid_bits) * ite_esz;
+ bool valid = false, last = false;

ret = scan_its_table(its, base, max_size, ite_esz, 0,
- vgic_its_restore_ite, dev);
+ vgic_its_restore_ite, dev, &valid, &last);
+
+ if (!ret && valid && !last) {
+ /* a next element was referenced but not found */
+ return -EINVAL;
+ }

return ret;
}
@@ -1985,29 +2018,29 @@ static int vgic_its_save_dte(struct vgic_its *its, struct its_device *dev,
* @id: device id the DTE corresponds to
* @ptr: kernel VA where the 8 byte DTE is located
* @opaque: unused
+ * @valid: indicates whether the dte is valid
*
* Return: < 0 on error, 0 if the dte is the last one, id offset to the
* next dte otherwise
*/
static int vgic_its_restore_dte(struct vgic_its *its, u32 id,
- void *ptr, void *opaque)
+ void *ptr, void *opaque, bool *valid)
{
struct its_device *dev;
gpa_t itt_addr;
u8 num_eventid_bits;
u64 entry = *(u64 *)ptr;
- bool valid;
u32 offset;
int ret;

entry = le64_to_cpu(entry);

- valid = entry >> KVM_ITS_DTE_VALID_SHIFT;
+ *valid = entry >> KVM_ITS_DTE_VALID_SHIFT;
num_eventid_bits = (entry & KVM_ITS_DTE_SIZE_MASK) + 1;
itt_addr = ((entry & KVM_ITS_DTE_ITTADDR_MASK)
>> KVM_ITS_DTE_ITTADDR_SHIFT) << 8;

- if (!valid)
+ if (!*valid)
return 1;

/* dte entry is valid */
@@ -2082,13 +2115,14 @@ static int vgic_its_save_device_tables(struct vgic_its *its)
* @id: index of the entry in the L1 table
* @addr: kernel VA
* @opaque: unused
+ * @valid: indicates whether any dte entry was found
*
* L1 table entries are scanned by steps of 1 entry
* Return < 0 if error, 0 if last dte was found when scanning the L2
* table, +1 otherwise (meaning next L1 entry must be scanned)
*/
static int handle_l1_dte(struct vgic_its *its, u32 id, void *addr,
- void *opaque)
+ void *opaque, bool *valid)
{
const struct vgic_its_abi *abi = vgic_its_get_abi(its);
int l2_start_id = id * (SZ_64K / abi->dte_esz);
@@ -2096,21 +2130,29 @@ static int handle_l1_dte(struct vgic_its *its, u32 id, void *addr,
int dte_esz = abi->dte_esz;
gpa_t gpa;
int ret;
+ bool last;

entry = le64_to_cpu(entry);

- if (!(entry & KVM_ITS_L1E_VALID_MASK))
+ *valid = entry & KVM_ITS_L1E_VALID_MASK;
+
+ if (!*valid)
return 1;

gpa = entry & KVM_ITS_L1E_ADDR_MASK;

ret = scan_its_table(its, gpa, SZ_64K, dte_esz,
- l2_start_id, vgic_its_restore_dte, NULL);
+ l2_start_id, vgic_its_restore_dte, NULL,
+ valid, &last);

- if (ret <= 0)
- return ret;
+ /*
+ * if the last dte has not been found in this L2 table, we
+ * need to scan the next L1 entry
+ */
+ if (!ret && !last)
+ return 1;

- return 1;
+ return ret;
}

/**
@@ -2124,6 +2166,7 @@ static int vgic_its_restore_device_tables(struct vgic_its *its)
int l1_esz, ret;
int l1_tbl_size = GITS_BASER_NR_PAGES(baser) * SZ_64K;
gpa_t l1_gpa;
+ bool valid = false, last = false;

if (!(baser & GITS_BASER_VALID))
return 0;
@@ -2133,15 +2176,17 @@ static int vgic_its_restore_device_tables(struct vgic_its *its)
if (baser & GITS_BASER_INDIRECT) {
l1_esz = GITS_LVL1_ENTRY_SIZE;
ret = scan_its_table(its, l1_gpa, l1_tbl_size, l1_esz, 0,
- handle_l1_dte, NULL);
+ handle_l1_dte, NULL, &valid, &last);
} else {
l1_esz = abi->dte_esz;
ret = scan_its_table(its, l1_gpa, l1_tbl_size, l1_esz, 0,
- vgic_its_restore_dte, NULL);
+ vgic_its_restore_dte, NULL, &valid, &last);
}

- if (ret > 0)
- ret = -EINVAL;
+ if (!ret && valid && !last) {
+ /* a next element was referenced but not found */
+ return -EINVAL;
+ }

return ret;
}
--
2.5.5