The commit adding the code fetching host CPU flags via the
KVM_GET_SUPPORTED_CPUID didn't describe at all why such an alghorithm is
needed.
Add a comment from the documentation outlining how the userspace
function is expected to allocate memory here.
Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
---
src/util/virhostcpu.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/src/util/virhostcpu.c b/src/util/virhostcpu.c
index 011ef8a153..6be00a5b76 100644
--- a/src/util/virhostcpu.c
+++ b/src/util/virhostcpu.c
@@ -1327,6 +1327,13 @@ virHostCPUGetCPUID(void)
return NULL;
}
+ /* Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure
+ * with the 'nent' field indicating the number of entries in the variable-size
+ * array 'entries'. If the number of entries is too low to describe the cpu
+ * capabilities, an error (E2BIG) is returned. If the number is too high,
+ * the 'nent' field is adjusted and an error (ENOMEM) is returned. If the
+ * number is just right, the 'nent' field is adjusted to the number of valid
+ * entries in the 'entries' array, which is then filled. */
for (i = 1; i < INT32_MAX; i *= 2) {
g_autofree struct kvm_cpuid2 *kvm_cpuid = NULL;
kvm_cpuid = g_malloc0(sizeof(struct kvm_cpuid2) +
--
2.35.1
