+ if (len > 0) {
+ ptr = mmap(NULL, len, prot, MAP_ANONYMOUS | MAP_SHARED, -1, 0);
+ if (ptr == MAP_FAILED) {
+ fprintf(stderr, "create_userspace_phys_mem: %s",
+ strerror(errno));
+ return 0;
+ }
You're using 'len == 0' here to change the semantics of the function.
It would be better to have two different APIs (perhaps sharing some of
the implementation by calling a helper).
Actually, this is a fix of a bug that is probably exposed only by the direct
mmio code.
Here is the problem (in the existing code):
kvm_destroy_phys_mem calls kvm_create_phys_mem(kvm, phys_start, 0, 0, 0);
kvm_create_phys_mem calls kvm_create_userspace_phys_mem which is calling
mmap(NULL, len, prot, MAP_ANONYMOUS | MAP_SHARED, -1, 0);
if (ptr == MAP_FAILED)
now, if len = 0 it fails.
We could have sent is as a separate patch,
and we could have made more changes to fix it differently,
for example, not to let kvm_destroy_phys_mem call kvm_create_phys_mem
(which seems strange in general...).
We wanted to minimize the amount of changes that we make, so we choose this
option.
What do you recommend?
Thanks,
Ben
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