[PATCH 19/22] KVM: arm/arm64: vgic: Don't rely on the wrong pending table

Marc Zyngier
2019-11-20T16:51:30Z

From: Zenghui Yu <yuzenghui@huawei.com>

It's possible that two LPIs locate in the same "byte_offset" but target
two different vcpus, where their pending status are indicated by two
different pending tables. In such a scenario, using last_byte_offset
optimization will lead KVM relying on the wrong pending table entry.
Let us use last_ptr instead, which can be treated as a byte index into
a pending table and also, can be vcpu specific.

Fixes: 280771252c1b ("KVM: arm64: vgic-v3: KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES")
Cc: stable@vger.kernel.org
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20191029071919.177-4-yuzenghui@huawei.com
---
virt/kvm/arm/vgic/vgic-v3.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index e69c538a24ca..f45635a6f0ec 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -363,8 +363,8 @@ int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq)
int vgic_v3_save_pending_tables(struct kvm *kvm)
{
struct vgic_dist *dist = &kvm->arch.vgic;
- int last_byte_offset = -1;
struct vgic_irq *irq;
+ gpa_t last_ptr = ~(gpa_t)0;
int ret;
u8 val;

@@ -384,11 +384,11 @@ int vgic_v3_save_pending_tables(struct kvm *kvm)
bit_nr = irq->intid % BITS_PER_BYTE;
ptr = pendbase + byte_offset;

- if (byte_offset != last_byte_offset) {
+ if (ptr != last_ptr) {
ret = kvm_read_guest_lock(kvm, ptr, &val, 1);
if (ret)
return ret;
- last_byte_offset = byte_offset;
+ last_ptr = ptr;
}

stored = val & (1U << bit_nr);