Re: [PATCH v3 33/34] KVM: selftests: hyperv_svm_test: Introduce L2 TLB flush test

[Maxim Levitsky <mlevitsk@redhat.com>]

On Thu, 2022-04-14 at 15:20 +0200, Vitaly Kuznetsov wrote:
> Enable Hyper-V L2 TLB flush and check that Hyper-V TLB flush hypercalls
> from L2 don't exit to L1 unless 'TlbLockCount' is set in the Partition
> assist page.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  .../selftests/kvm/x86_64/hyperv_svm_test.c    | 60 +++++++++++++++++--
>  1 file changed, 56 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c b/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c
> index 21f5ca9197da..99f0a2ead7df 100644
> --- a/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c
> @@ -42,11 +42,24 @@ struct hv_enlightenments {
>   */
>  #define VMCB_HV_NESTED_ENLIGHTENMENTS (1U << 31)
>  
> +#define HV_SVM_EXITCODE_ENL 0xF0000000
> +#define HV_SVM_ENL_EXITCODE_TRAP_AFTER_FLUSH   (1)
> +
>  static inline void vmmcall(void)
>  {
>  	__asm__ __volatile__("vmmcall");
>  }
>  
> +static inline void hypercall(u64 control, vm_vaddr_t arg1, vm_vaddr_t arg2)
> +{
> +	asm volatile("mov %3, %%r8\n"
> +		     "vmmcall"
> +		     : "+c" (control), "+d" (arg1)
> +		     :  "r" (arg2)
> +		     : "cc", "memory", "rax", "rbx", "r8", "r9", "r10",
> +		       "r11", "r12", "r13", "r14", "r15");
> +}

Yes, this code should really be put in a common file :)

> +
>  void l2_guest_code(void)
>  {
>  	GUEST_SYNC(3);
> @@ -62,11 +75,21 @@ void l2_guest_code(void)
>  
>  	GUEST_SYNC(5);
>  
> +	/* L2 TLB flush tests */
> +	hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE | HV_HYPERCALL_FAST_BIT, 0x0,
> +		  HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES | HV_FLUSH_ALL_PROCESSORS);
> +	rdmsr(MSR_FS_BASE);
> +	hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE | HV_HYPERCALL_FAST_BIT, 0x0,
> +		  HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES | HV_FLUSH_ALL_PROCESSORS);
> +	/* Make sure we're not issuing Hyper-V TLB flush call again */
> +	__asm__ __volatile__ ("mov $0xdeadbeef, %rcx");
> +
>  	/* Done, exit to L1 and never come back.  */
>  	vmmcall();
>  }
>  
> -static void __attribute__((__flatten__)) guest_code(struct svm_test_data *svm)
> +static void __attribute__((__flatten__)) guest_code(struct svm_test_data *svm,
> +						    vm_vaddr_t pgs_gpa)
>  {
>  	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
>  	struct vmcb *vmcb = svm->vmcb;
> @@ -75,13 +98,23 @@ static void __attribute__((__flatten__)) guest_code(struct svm_test_data *svm)
>  
>  	GUEST_SYNC(1);
>  
> -	wrmsr(HV_X64_MSR_GUEST_OS_ID, (u64)0x8100 << 48);
> +	wrmsr(HV_X64_MSR_GUEST_OS_ID, HYPERV_LINUX_OS_ID);
> +	wrmsr(HV_X64_MSR_HYPERCALL, pgs_gpa);
> +	enable_vp_assist(svm->vp_assist_gpa, svm->vp_assist);
>  
>  	GUEST_ASSERT(svm->vmcb_gpa);
>  	/* Prepare for L2 execution. */
>  	generic_svm_setup(svm, l2_guest_code,
>  			  &l2_guest_stack[L2_GUEST_STACK_SIZE]);
>  
> +	/* L2 TLB flush setup */
> +	hve->partition_assist_page = svm->partition_assist_gpa;
> +	hve->hv_enlightenments_control.nested_flush_hypercall = 1;
> +	hve->hv_vm_id = 1;
> +	hve->hv_vp_id = 1;
> +	current_vp_assist->nested_control.features.directhypercall = 1;
> +	*(u32 *)(svm->partition_assist) = 0;
> +
>  	GUEST_SYNC(2);
>  	run_guest(vmcb, svm->vmcb_gpa);
>  	GUEST_ASSERT(vmcb->control.exit_code == SVM_EXIT_VMMCALL);
> @@ -116,6 +149,20 @@ static void __attribute__((__flatten__)) guest_code(struct svm_test_data *svm)
>  	GUEST_ASSERT(vmcb->control.exit_code == SVM_EXIT_MSR);
>  	vmcb->save.rip += 2; /* rdmsr */
>  
> +
> +	/*
> +	 * L2 TLB flush test. First VMCALL should be handled directly by L0,
> +	 * no VMCALL exit expected.
> +	 */
> +	run_guest(vmcb, svm->vmcb_gpa);
> +	GUEST_ASSERT(vmcb->control.exit_code == SVM_EXIT_MSR);
> +	vmcb->save.rip += 2; /* rdmsr */
> +	/* Enable synthetic vmexit */
> +	*(u32 *)(svm->partition_assist) = 1;
> +	run_guest(vmcb, svm->vmcb_gpa);
> +	GUEST_ASSERT(vmcb->control.exit_code == HV_SVM_EXITCODE_ENL);
> +	GUEST_ASSERT(vmcb->control.exit_info_1 == HV_SVM_ENL_EXITCODE_TRAP_AFTER_FLUSH);
> +
>  	run_guest(vmcb, svm->vmcb_gpa);
>  	GUEST_ASSERT(vmcb->control.exit_code == SVM_EXIT_VMMCALL);
>  	GUEST_SYNC(6);
> @@ -126,7 +173,7 @@ static void __attribute__((__flatten__)) guest_code(struct svm_test_data *svm)
>  int main(int argc, char *argv[])
>  {
>  	vm_vaddr_t nested_gva = 0;
> -
> +	vm_vaddr_t hcall_page;
>  	struct kvm_vm *vm;
>  	struct kvm_run *run;
>  	struct ucall uc;
> @@ -141,7 +188,12 @@ int main(int argc, char *argv[])
>  	vcpu_set_hv_cpuid(vm, VCPU_ID);
>  	run = vcpu_state(vm, VCPU_ID);
>  	vcpu_alloc_svm(vm, &nested_gva);
> -	vcpu_args_set(vm, VCPU_ID, 1, nested_gva);
> +
> +	hcall_page = vm_vaddr_alloc_pages(vm, 1);
> +	memset(addr_gva2hva(vm, hcall_page), 0x0,  getpagesize());
> +
> +	vcpu_args_set(vm, VCPU_ID, 2, nested_gva, addr_gva2gpa(vm, hcall_page));
> +	vcpu_set_msr(vm, VCPU_ID, HV_X64_MSR_VP_INDEX, VCPU_ID);
>  
>  	for (stage = 1;; stage++) {
>  		_vcpu_run(vm, VCPU_ID);

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
	Maxim Levitsky