During some testing yesterday I realized that this patch actually
breaks the self test, causing an error which the later self test
changes cover up.
Running "./demand_paging_test -b 512M -u MINOR -s shmem -v 1" from
kvm/next (b3c98052d469) with just this patch applies gives the
following output
> # ./demand_paging_test -b 512M -u MINOR -s shmem -v 1
> Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages
> guest physical test memory: [0x7fcdfffe000, 0x7fcffffe000)
> Finished creating vCPUs and starting uffd threads
> Started all vCPUs
> ==== Test Assertion Failure ====
> demand_paging_test.c:50: false
> pid=13293 tid=13297 errno=4 - Interrupted system call
> // Some stack trace stuff
> Invalid guest sync status: exit_reason=UNKNOWN, ucall=0
The problem is the get_ucall() part of the following block in the self
test's vcpu_worker()
> ret = _vcpu_run(vcpu);
> TEST_ASSERT(ret == 0, "vcpu_run failed: %d\n", ret);
> if (get_ucall(vcpu, NULL) != UCALL_SYNC) {
> TEST_ASSERT(false,
> "Invalid guest sync status: exit_reason=%s\n",
> exit_reason_str(run->exit_reason));
> }
I took a look and, while get_ucall() does depend on the value of
exit_reason, the error's root cause isn't clear to me yet.
Moving the "exit_reason = kvm_exit_unknown" line to later in the
function, right above the vcpu_run() call "fixes" the problem. I've
done that for now and will bisect later to investigate: if anyone
has any clues please let me know.
