log_start might be called by memory.c just before registering the
section. So we can actually get a log_start without a region_add, which
we can silently ignore.
This makes current KVM code trigger an assertion
("kvm_section_update_flags: error finding slot").
Also, if we want to trap every access to a section, we might not have a
slot. So let's just tolerate if we don't have a slot.
Fixes: 343562e8fa22 ("kvm: kvm_log_start/stop are only called with known sections")
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
accel/kvm/kvm-all.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 90c88b517d..64de8461e0 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -394,8 +394,11 @@ static int kvm_section_update_flags(KVMMemoryListener *kml,
mem = kvm_lookup_matching_slot(kml, start_addr, size);
if (!mem) {
- fprintf(stderr, "%s: error finding slot\n", __func__);
- abort();
+ /*
+ * log_start() might be called before region_add(), and sometimes
+ * we don't have a slot as we want to trap every access.
+ */
+ return 0;
}
return kvm_slot_update_flags(kml, mem, section->mr);
--
2.13.5
On 16.10.2017 11:41, David Hildenbrand wrote: > log_start might be called by memory.c just before registering the > section. So we can actually get a log_start without a region_add, which > we can silently ignore. > > This makes current KVM code trigger an assertion > ("kvm_section_update_flags: error finding slot"). > > Also, if we want to trap every access to a section, we might not have a > slot. So let's just tolerate if we don't have a slot. > > Fixes: 343562e8fa22 ("kvm: kvm_log_start/stop are only called with known sections") > Reported-by: Thomas Huth <thuth@redhat.com> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > accel/kvm/kvm-all.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index 90c88b517d..64de8461e0 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -394,8 +394,11 @@ static int kvm_section_update_flags(KVMMemoryListener *kml, > > mem = kvm_lookup_matching_slot(kml, start_addr, size); > if (!mem) { > - fprintf(stderr, "%s: error finding slot\n", __func__); > - abort(); > + /* > + * log_start() might be called before region_add(), and sometimes > + * we don't have a slot as we want to trap every access. > + */ > + return 0; > } > > return kvm_slot_update_flags(kml, mem, section->mr); > I'll also send a patch for log_sync(), dropping the same assert. Looks like adding these assertions was counter productive :) -- Thanks, David
On 16/10/2017 11:53, David Hildenbrand wrote: > > Looks like adding these assertions was counter productive :) Or productive. Bugs happen, and if they are a good occasion to add new tests to the testsuite or at least a comment to the code, all the better. Paolo
On 16/10/2017 11:41, David Hildenbrand wrote: > log_start might be called by memory.c just before registering the > section. So we can actually get a log_start without a region_add, which > we can silently ignore. This is really a bug in memory.c, I think. When you put together everything as a single patch series, can you include the memory.c change instead, and drop this reference in the commit message and the kvm-all.c comment? Thanks, Paolo > This makes current KVM code trigger an assertion > ("kvm_section_update_flags: error finding slot"). > > Also, if we want to trap every access to a section, we might not have a > slot. So let's just tolerate if we don't have a slot.
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