Ping?
On 2018/5/16 17:18, Shannon Zhao wrote:
> According to KVM commit 75d61fbc, it needs to delete the slot before
> changing the KVM_MEM_READONLY flag. But QEMU commit 235e8982 only check
> whether KVM_MEM_READONLY flag is set instead of changing. It doesn't
> need to delete the slot if the KVM_MEM_READONLY flag is not changed.
>
> This fixes a issue that migrating a VM at the OVMF startup stage and
> VM is executing the codes in rom. Between the deleting and adding the
> slot in kvm_set_user_memory_region, there is a chance that guest access
> rom and trap to KVM, then KVM can't find the corresponding memslot.
> While KVM (on ARM) injects an abort to guest due to the broken hva, then
> guest will get stuck.
>
> Signed-off-by: Shannon Zhao <zhaoshenglong@xxxxxxxxxx>
> ---
> include/sysemu/kvm_int.h | 1 +
> kvm-all.c | 6 +++---
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
> index 888557a..f838412 100644
> --- a/include/sysemu/kvm_int.h
> +++ b/include/sysemu/kvm_int.h
> @@ -20,6 +20,7 @@ typedef struct KVMSlot
> void *ram;
> int slot;
> int flags;
> + int old_flags;
> } KVMSlot;
>
> typedef struct KVMMemoryListener {
> diff --git a/kvm-all.c b/kvm-all.c
> index 2515a23..de8250e 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -252,7 +252,7 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot)
> mem.userspace_addr = (unsigned long)slot->ram;
> mem.flags = slot->flags;
>
> - if (slot->memory_size && mem.flags & KVM_MEM_READONLY) {
> + if (slot->memory_size && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) {
> /* Set the slot size to 0 before setting the slot to the desired
> * value. This is needed based on KVM commit 75d61fbc. */
> mem.memory_size = 0;
> @@ -376,11 +376,11 @@ static int kvm_slot_update_flags(KVMMemoryListener *kml, KVMSlot *mem,
> {
> int old_flags;
>
> - old_flags = mem->flags;
> + mem->old_flags = mem->flags;
> mem->flags = kvm_mem_flags(mr);
>
> /* If nothing changed effectively, no need to issue ioctl */
> - if (mem->flags == old_flags) {
> + if (mem->flags == mem->old_flags) {
> return 0;
> }
>
>
--
Shannon
