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b18ee21055
KVM_CAP_VM_TYPES advertises the bitmap of VM types that KVM_CREATE_VM
accepts, but nothing verified that the ioctl actually enforces it: that
every advertised type can be created and every non-advertised type is
rejected. sev_init2_tests carried a TODO for this ("check that
unsupported types cannot be created. Probably a separate selftest"),
but the check is not specific to SEV or KVM_SEV_INIT2, and not even to
x86.
Add a standalone test that walks the type space and, for each value,
asserts that KVM_CREATE_VM succeeds iff the corresponding bit is set in
KVM_CAP_VM_TYPES, and otherwise fails with -EINVAL. The walk extends
past bit 31 so that out-of-range type values, which can never be
advertised in the u32 bitmap, are also confirmed to be rejected. The
test only depends on KVM_CAP_VM_TYPES, so it lives in the common set and
is skipped on architectures that don't advertise the capability.
Drop the now-addressed TODO from sev_init2_tests.c.
Tested on an AMD SEV-SNP capable host. With KVM_CAP_VM_TYPES=0x15
(DEFAULT/SEV/SNP), only the advertised types are created and everything
else is rejected:
$ strace -e trace=ioctl ./vm_types_test 2>&1 | grep KVM_CREATE_VM
ioctl(3, KVM_CREATE_VM, 0) = 4 # DEFAULT
ioctl(3, KVM_CREATE_VM, 0x1) = -1 EINVAL # SW_PROTECTED
ioctl(3, KVM_CREATE_VM, 0x2) = 4 # SEV
ioctl(3, KVM_CREATE_VM, 0x3) = -1 EINVAL # SEV-ES
ioctl(3, KVM_CREATE_VM, 0x4) = 4 # SNP
ioctl(3, KVM_CREATE_VM, 0x5) = -1 EINVAL # TDX
... 0x6..0x3f all -1 EINVAL ...
Reloading kvm_amd with sev_snp=0 drops the bitmap to 0x5 and only types
0 and 2 are then created, confirming the test tracks the advertised set
rather than hard-coded types.
Signed-off-by: Hemanth Selam <hemanth.selam@gmail.com>
Link: https://patch.msgid.link/20260710050442.826777-1-hemanth.selam@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>