In device tables/ITTs, DTEs/ITEs are implemented as a static single
linked list. But the head of the list might not be the first DTE/ITE in
the table. That's why in the restore operation, the DTs/ITTs have to be
scanned to find the first valid DTE/ITE (head of the list).
Add a dummy DTE/ITE in the first entry of the table if the first entry
doesn't have a valid DTE/ITE. This dummy DTE/ITE points to the first
valid DTE/ITE if there is a valid one.
This change paves the way for future incoming changes which will utilize
the fixed head the DTE/ITE list to avoid scanning uncessary table
entries.
No functional change intended.
Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx>
---
arch/arm64/kvm/vgic/vgic-its.c | 56 ++++++++++++++++++++++++++++++++--
arch/arm64/kvm/vgic/vgic.h | 6 ++++
2 files changed, 59 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index ba945ba78cc7..953af024d94a 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -2176,10 +2176,12 @@ static int vgic_its_ite_cmp(void *priv, const struct list_head *a,
static int vgic_its_save_itt(struct vgic_its *its, struct its_device *device)
{
const struct vgic_its_abi *abi = vgic_its_get_abi(its);
+ struct its_ite *ite, *first_ite = NULL;
+ struct kvm *kvm = its->dev->kvm;
gpa_t base = device->itt_addr;
- struct its_ite *ite;
- int ret;
int ite_esz = abi->ite_esz;
+ u64 val = 0;
+ int ret;
list_sort(NULL, &device->itt_head, vgic_its_ite_cmp);
@@ -2198,7 +2200,24 @@ static int vgic_its_save_itt(struct vgic_its *its, struct its_device *device)
ret = vgic_its_save_ite(its, device, ite, gpa, ite_esz);
if (ret)
return ret;
+
+ if (!first_ite)
+ first_ite = ite;
}
+
+ /*
+ * As for DTEs, add a dummy ITE if necessary for ITT to avoid uncessary
+ * sanning in the store operation.
+ */
+ if (first_ite && first_ite->event_id)
+ val = (u64)first_ite->event_id << KVM_ITS_ITE_NEXT_SHIFT;
+
+ if (!first_ite || first_ite->event_id) {
+ val |= KVM_ITS_ENTRY_DUMMY_MAGIC << KVM_ITS_ENTRY_DUMMY_SHIFT;
+ val = cpu_to_le64(val);
+ vgic_write_guest_lock(kvm, base, &val, ite_esz);
+ }
+
return 0;
}
@@ -2328,8 +2347,11 @@ static int vgic_its_save_device_tables(struct vgic_its *its)
{
const struct vgic_its_abi *abi = vgic_its_get_abi(its);
u64 baser = its->baser_device_table;
- struct its_device *dev;
+ struct its_device *dev, *first_dev = NULL;
+ struct kvm *kvm = its->dev->kvm;
int dte_esz = abi->dte_esz;
+ gpa_t dummy_eaddr;
+ u64 val = 0;
if (!(baser & GITS_BASER_VALID))
return 0;
@@ -2351,7 +2373,35 @@ static int vgic_its_save_device_tables(struct vgic_its *its)
ret = vgic_its_save_dte(its, dev, eaddr, dte_esz);
if (ret)
return ret;
+
+ if (!first_dev)
+ first_dev = dev;
}
+
+ /*
+ * The valid DTEs in the device table are linked with a static single
+ * linked list, but the list head is not always the first DTE. That's
+ * why the restore operation has to scan the device table from the first
+ * entry all the time.
+ * To avoid the uncessary scanning in the restore operation, if the
+ * first valid DTE is not the first one in the table, add a dummy DTE
+ * with valid bit as 0 pointing to the first valid DTE.
+ * This way, the first DTE in the table is always the head of the DTE
+ * list. It is either a valid DTE or a dummy DTE (V= 0) pointing to the
+ * first valid DTE if there is a valid DTE in the table.
+ */
+ if (first_dev && first_dev->device_id)
+ val = (u64)first_dev->device_id << KVM_ITS_DTE_DUMMY_NEXT_SHIFT;
+
+ if (!first_dev || first_dev->device_id) {
+ if (!vgic_its_check_id(its, baser, 0, &dummy_eaddr))
+ return -EINVAL;
+
+ val |= KVM_ITS_ENTRY_DUMMY_MAGIC << KVM_ITS_ENTRY_DUMMY_SHIFT;
+ val = cpu_to_le64(val);
+ vgic_write_guest_lock(kvm, dummy_eaddr, &val, dte_esz);
+ }
+
return 0;
}
diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h
index f2486b4d9f95..93314f249343 100644
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -86,6 +86,12 @@
#define KVM_ITS_L1E_VALID_MASK BIT_ULL(63)
/* we only support 64 kB translation table page size */
#define KVM_ITS_L1E_ADDR_MASK GENMASK_ULL(51, 16)
+/* Macros for dummy ITE/DTE */
+#define KVM_ITS_ENTRY_DUMMY_SHIFT 0
+#define KVM_ITS_ENTRY_DUMMY_MASK GENMASK_ULL(15, 0)
+#define KVM_ITS_ENTRY_DUMMY_MAGIC 0xdafe
+#define KVM_ITS_DTE_DUMMY_NEXT_SHIFT 16
+#define KVM_ITS_DTE_DUMMY_NEXT_MASK GENMASK(48, 16)
#define KVM_VGIC_V3_RDIST_INDEX_MASK GENMASK_ULL(11, 0)
#define KVM_VGIC_V3_RDIST_FLAGS_MASK GENMASK_ULL(15, 12)
--
2.47.0.199.ga7371fff76-goog
