A handful of nits, but no need for another version, I'll fixup when applying.
Thanks!
On Fri, Jul 10, 2026, Hemanth Selam wrote:
> diff --git a/tools/testing/selftests/kvm/vm_types_test.c
> b/tools/testing/selftests/kvm/vm_types_test.c
> new file mode 100644
> index 000000000000..e8ef3b018f6c
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/vm_types_test.c
> @@ -0,0 +1,50 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Verify that KVM_CREATE_VM accepts exactly the VM types enumerated by
> + * KVM_CAP_VM_TYPES, and rejects every other type with -EINVAL.
> + */
> +#include <errno.h>
> +#include <stdbool.h>
> +#include <unistd.h>
> +
> +#include <linux/kvm.h>
> +
> +#include "kvm_util.h"
> +#include "test_util.h"
> +
> +int main(void)
> +{
> + unsigned int supported_types;
> + unsigned long type;
> + int kvm_fd, fd;
Probably worth declaring "fd" inside the for-loop. Definitely a coin toss on
which is "better".
> + TEST_REQUIRE(kvm_has_cap(KVM_CAP_VM_TYPES));
> +
> + kvm_fd = open_kvm_dev_path_or_exit();
> + supported_types = kvm_check_cap(KVM_CAP_VM_TYPES);
> + pr_info("KVM_CAP_VM_TYPES: 0x%x\n", supported_types);
Rather than "KVM_CAP_VM_TYPES" print a more human friendly message, e.g.
"Supported VM Types: ", otherwise it's not entirely obvious that the message is
printing the result of KVM_CAP_VM_TYPES version the raw macro number.
> +
> + /*
> + * KVM_CAP_VM_TYPES is a u32 bitmap, so only types 0..31 can ever be
> + * advertised. Walk past that range as well to confirm that any
> + * out-of-range type is rejected rather than silently accepted.
Rather than lean on KVM internals, I think it makes sense to express this
limitation
in terms of KVM_CHECK_EXTENSION's return values. Which is still kinda sorta an
internal detail, but it's at least more visible to userspace.
Specifically, track supported_types as an "unsigned long", and then have the
comment talk about KVM's deliberately retristed return value, not how KVM tracks
its supported types internally. As a bonus, the loop can iterate on the bits
per
supported_types, not a hardcoded "64".
/*
* For compatibility with 32-bit kernels, KVM_CHECK_EXTENSION restricts
* its return to 32-bit values, i.e. only types 0..31 can be advertised.
* Walk past that range as well to confirm that any out-of-range type is
* rejected rather than silently accepted (or truncated).
*/
for (type = 0; type < BITS_PER_TYPE(supported_types); type++) {
> + */
> + for (type = 0; type < 64; type++) {
> + bool supported = type < 32 && (supported_types & (1U << type));
And then if supported_types is an "unsigned long", the "type < 32" goes away.
A bonus to _that_ is that the test will Just Work if future KVM does enumerate
support for types > 31.
The bitwise-AND can also use BIT().
> +
> + fd = __kvm_ioctl(kvm_fd, KVM_CREATE_VM, (void *)type);
> +
> + if (supported) {
> + TEST_ASSERT(fd >= 0,
> + "KVM_CREATE_VM(%lu) should succeed,
> KVM_CAP_VM_TYPES=0x%x",
> + type, supported_types);
> + close(fd);
kvm_close()
> + } else {
> + TEST_ASSERT(fd < 0 && errno == EINVAL,
> + "KVM_CREATE_VM(%lu) should fail with
> EINVAL, KVM_CAP_VM_TYPES=0x%x",
> + type, supported_types);
> + }
> + }
> +
> + return 0;
> +}
> diff --git a/tools/testing/selftests/kvm/x86/sev_init2_tests.c
> b/tools/testing/selftests/kvm/x86/sev_init2_tests.c
> index 8db88c355f16..d4227dc922ab 100644
> --- a/tools/testing/selftests/kvm/x86/sev_init2_tests.c
> +++ b/tools/testing/selftests/kvm/x86/sev_init2_tests.c
> @@ -77,10 +77,6 @@ void test_vm_types(void)
> {
> test_init2(KVM_X86_SEV_VM, &(struct kvm_sev_init){});
>
> - /*
> - * TODO: check that unsupported types cannot be created. Probably
> - * a separate selftest.
> - */
> if (have_sev_es)
> test_init2(KVM_X86_SEV_ES_VM, &(struct kvm_sev_init){});
>
> --
> 2.43.7
>
