On 6/7/22 19:44, Dr. David Alan Gilbert wrote:
+ return NULL;
+ }
+ descriptors->kvm_stats_header = kvm_stats_header;
+ descriptors->kvm_stats_desc = kvm_stats_desc;
+ descriptors->ident = g_strdup(ident);
There's something that confuses me here; you check your set of
descriptors above to find any with the matching ident, and if you've
already got it you return it; OK. Now, if you don't match then you
read some stats and store it with that ident - but I don't see
when you read the stats from the fd, what makes it read the stats that
correspond to 'ident' ?
If you mean why not some other source, each source has a different file
descriptor:
+ int stats_fd = kvm_vcpu_ioctl(cpu, KVM_GET_STATS_FD, NULL);
but the descriptors are consistent every time KVM_GET_STATS_FD is
called, so basically "ident" can be used as a cache key.
If you mean how does it access the right stat, here it uses the offset
field in the descriptor
ret = pread(stats_fd, stats_data, size_data,
kvm_stats_header->data_offset);
...
for (i = 0; i < kvm_stats_header->num_desc; ++i) {
uint64_t *stats;
pdesc = (void *)kvm_stats_desc + i * size_desc;
/* Add entry to the list */
stats = (void *)stats_data + pdesc->offset;
Paolo
