On Wed, Dec 13, 2023, Paolo Bonzini wrote: > 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. Wait, what? How does double underscores exempt it from being uAPI? AIUI, the C standard effectively ensures that userspace won't define/declare symbols with double underscores, i.e. ensures there won't be conflicts. But pretty much all of the kernel-defined types are prefixed with "__", e.g. __u8 and friends, so I don't see how prefixing with "__" exempts something from becoming uAPI. I completely agree that __KVM_HAVE_READONLY_MEM shouldn't be uAPI, but then it really, really shouldn't be defined in arch/x86/include/uapi/asm/kvm.h.
