Re: [PATCH] KVM: selftests: fix triple fault if ept=0 in dirty_log_test

[Paolo Bonzini <pbonzini@redhat.com>]

On 22/06/21 15:55, Hou Wenlong wrote:
> Commit 22f232d134e1 ("KVM: selftests: x86: Set supported CPUIDs on
> default VM") moved vcpu_set_cpuid into vm_create_with_vcpus, but
> dirty_log_test doesn't use it to create vm. So vcpu's CPUIDs is
> not set, the guest's pa_bits in kvm would be smaller than the
> value queried by userspace.
> 
> However, the dirty track memory slot is in the highest GPA, the
> reserved bits in gpte would be set with wrong pa_bits.
> For shadowpaing, page fault would fail in permission_fault and
> be injected into guest. Since guest doesn't have idt, it finally
> leads to vm_exit for triple fault.
> 
> Move vcpu_set_cpuid into vm_vcpu_add_default to set supported
> CPUIDs on default vcpu, since almost all tests need it.
> 
> Fixes: 22f232d134e1 ("KVM: selftests: x86: Set supported CPUIDs on default VM")
> Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com>
> ---
>   tools/testing/selftests/kvm/lib/kvm_util.c         | 4 ----
>   tools/testing/selftests/kvm/lib/x86_64/processor.c | 3 +++
>   tools/testing/selftests/kvm/steal_time.c           | 2 --
>   3 files changed, 3 insertions(+), 6 deletions(-)

Queued, but this is missing:

diff --git a/tools/testing/selftests/kvm/x86_64/set_boot_cpu_id.c b/tools/testing/selftests/kvm/x86_64/set_boot_cpu_id.c
index 5f8dd74d415f..fd309fb9e2c4 100644
--- a/tools/testing/selftests/kvm/x86_64/set_boot_cpu_id.c
+++ b/tools/testing/selftests/kvm/x86_64/set_boot_cpu_id.c
@@ -102,8 +102,6 @@ static void add_x86_vcpu(struct kvm_vm *vm, uint32_t vcpuid, bool bsp_code)
  		vm_vcpu_add_default(vm, vcpuid, guest_bsp_vcpu);
  	else
  		vm_vcpu_add_default(vm, vcpuid, guest_not_bsp_vcpu);
-
-	vcpu_set_cpuid(vm, vcpuid, kvm_get_supported_cpuid());
  }
  
  static void run_vm_bsp(uint32_t bsp_vcpu)

Paolo

> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index a2b732cf96ea..8ea854d7822d 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -375,10 +375,6 @@ struct kvm_vm *vm_create_with_vcpus(enum vm_guest_mode mode, uint32_t nr_vcpus,
>   		uint32_t vcpuid = vcpuids ? vcpuids[i] : i;
>   
>   		vm_vcpu_add_default(vm, vcpuid, guest_code);
> -
> -#ifdef __x86_64__
> -		vcpu_set_cpuid(vm, vcpuid, kvm_get_supported_cpuid());
> -#endif
>   	}
>   
>   	return vm;
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> index efe235044421..595322b24e4c 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> @@ -600,6 +600,9 @@ void vm_vcpu_add_default(struct kvm_vm *vm, uint32_t vcpuid, void *guest_code)
>   	/* Setup the MP state */
>   	mp_state.mp_state = 0;
>   	vcpu_set_mp_state(vm, vcpuid, &mp_state);
> +
> +	/* Setup supported CPUIDs */
> +	vcpu_set_cpuid(vm, vcpuid, kvm_get_supported_cpuid());
>   }
>   
>   /*
> diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
> index fcc840088c91..a6fe75cb9a6e 100644
> --- a/tools/testing/selftests/kvm/steal_time.c
> +++ b/tools/testing/selftests/kvm/steal_time.c
> @@ -73,8 +73,6 @@ static void steal_time_init(struct kvm_vm *vm)
>   	for (i = 0; i < NR_VCPUS; ++i) {
>   		int ret;
>   
> -		vcpu_set_cpuid(vm, i, kvm_get_supported_cpuid());
> -
>   		/* ST_GPA_BASE is identity mapped */
>   		st_gva[i] = (void *)(ST_GPA_BASE + i * STEAL_TIME_SIZE);
>   		sync_global_to_guest(vm, st_gva[i]);
>