On 12/13/23 18:21, Sean Christopherson wrote:
On Tue, Dec 12, 2023, Paolo Bonzini wrote:
On 12/9/23 03:29, Sean Christopherson wrote:
On Fri, Dec 08, 2023, Paolo Bonzini wrote:
KVM/Arm supports readonly memslots; fix the calculation of
supported_flags in set_memory_region_test.c, otherwise the
test fails.
You got beat by a few hours, and by a better solution ;-)
https://lore.kernel.org/all/20231208033505.2930064-1-shahuang@xxxxxxxxxx
Better but also wrong---and my patch has the debatable merit of more
clearly exposing the wrongness. Testing individual architectures is bad,
but testing __KVM_HAVE_READONLY_MEM makes the test fail when running a new
test on an old kernel.
But we already crossed that bridge and burned it for good measure by switching
to KVM_SET_USER_MEMORY_REGION2, i.e. as of commit
8d99e347c097 ("KVM: selftests: Convert lib's mem regions to KVM_SET_USER_MEMORY_REGION2")
selftests built against a new kernel can't run on an old kernel. Building KVM
selftests requires kernel headers, so while not having a hard requirement that
the uapi headers are fresh would be nice, I don't think it buys all that much.
If we wanted to assert that x86, arm64, etc. enumerate __KVM_HAVE_READONLY_MEM,
i.e. ensure that read-only memory is supported as expected, then that can be done
as a completely unrelated test.
selftests have the luxury of having sync-ed kernel headers, but in
general userspace won't, and that means __KVM_HAVE_READONLY_MEM would be
a very poor userspace API. Fortunately it has "__" so it is not
userspace API at all, and I don't want selftests to treat it as one.
IMO, one of the big selling points of selftests over KUT is that we can punt on
supporting old kernels since selftests are in-tree. I don't think it's at all
unreasonable to require that selftests be built against the target kernel, and
by doing so we can signficantly reduce the maintenance burden. The kernel needs
to be backwards compatibile, but I don't see why selftests need to be backwards
compatible.
It does help sometimes to be able to run old tests on new kernel or vice
versa. So even without making that a requirement, it is a nice thing to
have whenever possible.
Paolo
