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KVM: selftests: Verify KVM is loaded when getting a KVM module param

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Probe /dev/kvm when getting a KVM module param so that attempting to load
a module param super early in a selftest generates a SKIP message about
KVM not being loaded/enabled, versus some random parameter not existing.

E.g. KVM x86's unconditional retrieval of force_emulation_prefix during
kvm_selftest_arch_init() generates a rather confusing error message that
takes far too much triage to understand.

Link: https://lore.kernel.org/r/20250516215909.2551628-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2025-05-16 14:59:06 -07:00
parent 30142a93b1
commit fcab107abe
4 changed files with 9 additions and 12 deletions
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6
tools/testing/selftests/kvm/include/x86/processor.h
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@@ -1150,7 +1150,6 @@ do { \
void kvm_get_cpu_address_width(unsigned int *pa_bits, unsigned int *va_bits);
void kvm_init_vm_address_properties(struct kvm_vm *vm);
bool vm_is_unrestricted_guest(struct kvm_vm *vm);
struct ex_regs {
uint64_t rax, rcx, rdx, rbx;
@@ -1325,6 +1324,11 @@ static inline bool kvm_is_forced_emulation_enabled(void)
return !!get_kvm_param_integer("force_emulation_prefix");
}
static inline bool kvm_is_unrestricted_guest_enabled(void)
{
return get_kvm_intel_param_bool("unrestricted_guest");
}
uint64_t *__vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr,
int *level);
uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr);

3
tools/testing/selftests/kvm/lib/kvm_util.c
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@@ -64,6 +64,9 @@ static ssize_t get_module_param(const char *module_name, const char *param,
ssize_t bytes_read;
int fd, r;
/* Verify KVM is loaded, to provide a more helpful SKIP message. */
close(open_kvm_dev_path_or_exit());
r = snprintf(path, path_size, "/sys/module/%s/parameters/%s",
module_name, param);
TEST_ASSERT(r < path_size,

10
tools/testing/selftests/kvm/lib/x86/processor.c
View File

@@ -1264,16 +1264,6 @@ done:
return min(max_gfn, ht_gfn - 1);
}
/* Returns true if kvm_intel was loaded with unrestricted_guest=1. */
bool vm_is_unrestricted_guest(struct kvm_vm *vm)
{
/* Ensure that a KVM vendor-specific module is loaded. */
if (vm == NULL)
close(open_kvm_dev_path_or_exit());
return get_kvm_intel_param_bool("unrestricted_guest");
}
void kvm_selftest_arch_init(void)
{
host_cpu_is_intel = this_cpu_is_intel();

2
tools/testing/selftests/kvm/x86/vmx_exception_with_invalid_guest_state.c
View File

@@ -110,7 +110,7 @@ int main(int argc, char *argv[])
struct kvm_vm *vm;
TEST_REQUIRE(host_cpu_is_intel);
TEST_REQUIRE(!vm_is_unrestricted_guest(NULL));
TEST_REQUIRE(!kvm_is_unrestricted_guest_enabled());
vm = vm_create_with_one_vcpu(&vcpu, guest_code);
get_set_sigalrm_vcpu(vcpu);