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Subject[PATCH 2/4] KVM: arm64: Allow saving vgic3 pending tables in no running vcpu context
Date
It's possible to save vgic3 pending tables in no running VCPU
context. This is another unknown case detected by 'kvm-unit-tests'.

# ./kvm-unit-tests/tests/its-pending-migration
WARNING: CPU: 120 PID: 7973 at arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3325 \
mark_page_dirty_in_slot+0x60/0xe0
:
mark_page_dirty_in_slot+0x60/0xe0
__kvm_write_guest_page+0xcc/0x100
kvm_write_guest+0x7c/0xb0
vgic_v3_save_pending_tables+0x148/0x2a0
vgic_set_common_attr+0x158/0x240
vgic_v3_set_attr+0x4c/0x5c
kvm_device_ioctl+0x100/0x160
__arm64_sys_ioctl+0xa8/0xf0
invoke_syscall.constprop.0+0x7c/0xd0
el0_svc_common.constprop.0+0x144/0x160
do_el0_svc+0x34/0x60
el0_svc+0x3c/0x1a0
el0t_64_sync_handler+0xb4/0x130
el0t_64_sync+0x178/0x17c

Fix it by allowing to save VGIC3 pending tables in no running VCPU
context.

Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
---
Documentation/virt/kvm/api.rst | 3 +++
arch/arm64/kvm/vgic/vgic-v3.c | 2 ++
2 files changed, 5 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 18b245a0ba02..7cf3d4b77703 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8074,6 +8074,9 @@ NOTE: One example of using the backup bitmap is saving arm64 vgic/its
tables and vgic3 LPI pending status through KVM_DEV_ARM_{VGIC_GRP_CTRL,
ITS_SAVE_TABLES} and KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_RESTORE_TABLES}
command on KVM device "kvm-arm-vgic-its" when dirty ring is enabled.
+The backup bitmap is also used when vgic3 pending table is saved
+through KVM_DEV_ARM_{VGIC_GRP_CTRL, VGIC_SAVE_PENDING_TABLES} command
+on KVM device "kvm-arm-vgic-v3".

8.30 KVM_CAP_XEN_HVM
--------------------
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 32998c8587a8..1e6b5f19d524 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -440,7 +440,9 @@ int vgic_v3_save_pending_tables(struct kvm *kvm)
else
val &= ~(1 << bit_nr);

+ dist->save_vgic_v3_tables_in_progress = true;
ret = kvm_write_guest_lock(kvm, ptr, &val, 1);
+ dist->save_vgic_v3_tables_in_progress = false;
if (ret)
goto out;
}
--
2.23.0
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