On Wed, Mar 17, 2021 at 12:25:52PM +0100, Emanuele Giuseppe Esposito wrote:
>
>
> On 17/03/2021 11:49, Paolo Bonzini wrote:
> > On 17/03/21 08:45, Emanuele Giuseppe Esposito wrote:
> > > + struct kvm_msr_list features_list;
> > > buffer.header.nmsrs = 1;
> > > buffer.entry.index = msr_index;
> > > + features_list.nmsrs = 1;
> > > +
> > > kvm_fd = open(KVM_DEV_PATH, O_RDONLY);
> > > if (kvm_fd < 0)
> > > exit(KSFT_SKIP);
> > > + r = ioctl(kvm_fd, KVM_GET_MSR_FEATURE_INDEX_LIST, &features_list);
> > > + TEST_ASSERT(r < 0 && r != -E2BIG,
> > > "KVM_GET_MSR_FEATURE_INDEX_LIST IOCTL failed,\n"
> > > + " rc: %i errno: %i", r, errno);
> >
> > Careful: because this has nsmrs == 1, you are overwriting an u32 of the
> > stack after struct kvm_msr_list. You need to use your own struct
> > similar to what is done with "buffer.header" and "buffer.entry".
> >
> > > r = ioctl(kvm_fd, KVM_GET_MSRS, &buffer.header);
> > > TEST_ASSERT(r == 1, "KVM_GET_MSRS IOCTL failed,\n"
> > > " rc: %i errno: %i", r, errno);
> > >
> >
> > More in general, this is not a test, but rather a library function used
> > to read a single MSR.
> >
> > If you would like to add a test for KVM_GET_MSR_FEATURE_INDEX_LIST that
> > would be very welcome. That would be a new executable. Looking at the
> > logic for the ioctl, the main purpose of the test should be:
> >
> > - check that if features_list.nmsrs is too small it will set the nmsrs
> > field and return -E2BIG.
> >
> > - check that all MSRs returned by KVM_GET_MSR_FEATURE_INDEX_LIST can be
> > accessed with KVM_GET_MSRS
> >
> > So something like this:
> >
> > set nmsrs to 0 and try the ioctl
> > check that it returns -E2BIG and has changed nmsrs
> > if nmsrs != 1 {
> > set nmsrs to 1 and try the ioctl again
> > check that it returns -E2BIG
> > }
> > malloc a buffer with room for struct kvm_msr_list and nmsrs indices
> > set nmsrs in the malloc-ed buffer and try the ioctl again
> > for each index
> > invoke kvm_get_feature_msr to read it
> >
> > (The test should also be skipped if KVM does not expose the
> > KVM_CAP_GET_MSR_FEATURES capability).
>
> Thank you for the feedback, the title is indeed a little bit misleading. My
> idea in this patch was to just add an additional check to all usages of
> KVM_GET_MSRS, since KVM_GET_MSR_FEATURE_INDEX_LIST is used only to probe
> host capabilities and processor features.
> But you are right, a separate test would be better.
>
Hi Emanuele,
You might be able to get some inspiration from the aarch64/get-reg-list.c
test. The list of MSRs varies with KVM version and host processor, but
there may be a set of MSRs that does not vary with host processor and
should not be removed in later KVM versions. If that's the case, then
the !missing_regs assert concept of aarch64/get-reg-list.c may also
apply to this new test. Based on Paolo's comment, I presume at least the
!failed_get should apply. Finally, the test should do the E2BIG checks,
as Paolo states, but you may also want to create a lib function for
KVM_GET_MSR_FEATURE_INDEX_LIST, similar to vcpu_get_reg_list(), if you
think it may be of use to other tests.
Thanks,
drew
