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fix return check for KVM_GET_DIRTY_LOG ioctl

PATCH Applied Mario Smarduch 2 participants 3 messages Mar 19, 2014 – Mar 20, 2014

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Mario Smarduch

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#0 lore raw

PATCH 1/1 fix return check for KVM_GET_DIRTY_LOG ioctl

Fix return condition check from kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) to handle internal failures or no support for memory slot dirty bitmap. Otherwise the ioctl succeeds and continues with migration. Addresses BUG# 1294227

Signed-off-by Mario Smarduch <[email protected]>
---
 kvm-all.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
kvm-all.c +1 -1
index 82a9119..cd4111d 100644
@@ -441,7 +441,7 @@ static int kvm_physical_sync_dirty_bitmap(MemoryRegionSection *section)
 
         d.slot = mem->slot;
 
-        if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) {
+        if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) < 0) {
             DPRINTF("ioctl failed %d\n", errno);
             ret = -1;
             break;
Signature · 1 line
1.7.9.5
Applied
#1 lore raw
Quoted 5 lines · Mario Smarduch

Fix return condition check from kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) to handle internal failures or no support for memory slot dirty bitmap. Otherwise the ioctl succeeds and continues with migration. Addresses BUG# 1294227

Thanks, applied to -trivial.

[]

kvm-all.c static int kvm_physical_sync_dirty_bitmap(MemoryRegionSection *section) · line 444

Quoted 2 lines
kvm-all.c +1 -1
-        if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) {
+        if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) < 0) {

Actually I'd make all error checks like this. Many checks compares return value with -1 for some reason, while actually, any <0 value should be treated as error in many many places... At the same time, comparison with 0 is cheaper than comparison with -1 ;)

/mjt

author
#2 lore raw

I agree. One thing I forgot to mention andother side effect of this bug was virtio VRing used, avail index error the Guest was 1,2,.. less then host.

I looked up that bug it happend on some architectures. This may or may not be related. Obviously if the dirty bitmap is not processed properly you may see issues like that.

- Mario

Quoted 20 lines · Michael Tokarev
Quoted 5 lines · Mario Smarduch

Fix return condition check from kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) to handle internal failures or no support for memory slot dirty bitmap. Otherwise the ioctl succeeds and continues with migration. Addresses BUG# 1294227

Thanks, applied to -trivial.

[]

kvm-all.c static int kvm_physical_sync_dirty_bitmap(MemoryRegionSection *section) · line 444

Quoted 2 lines
kvm-all.c +1 -1
-        if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) {
+        if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) < 0) {

Actually I'd make all error checks like this. Many checks compares return value with -1 for some reason, while actually, any <0 value should be treated as error in many many places... At the same time, comparison with 0 is cheaper than comparison with -1 ;)

/mjt