linux-kernel - Re: [PATCH 1/3] selftests: kvm: add a SVM version of state-test

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Date:   Wed, 20 May 2020 18:50:07 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     oupton@...gle.com
Subject: Re: [PATCH 1/3] selftests: kvm: add a SVM version of state-test

Paolo Bonzini <pbonzini@...hat.com> writes:

> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  .../testing/selftests/kvm/x86_64/state_test.c | 65 ++++++++++++++++---
>  1 file changed, 55 insertions(+), 10 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/state_test.c b/tools/testing/selftests/kvm/x86_64/state_test.c
> index 5b1a016edf55..1c5216f1ef0a 100644
> --- a/tools/testing/selftests/kvm/x86_64/state_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/state_test.c
> @@ -18,10 +18,42 @@
>  #include "kvm_util.h"
>  #include "processor.h"
>  #include "vmx.h"
> +#include "svm_util.h"
>  
>  #define VCPU_ID		5
> +#define L2_GUEST_STACK_SIZE 64
> +
> +void svm_l2_guest_code(void)
> +{
> +	GUEST_SYNC(4);
> +        /* Exit to L1 */
> +	vmcall();
> +	GUEST_SYNC(6);
> +	/* Done, exit to L1 and never come back.  */
> +	vmcall();
> +}
> +
> +static void svm_l1_guest_code(struct svm_test_data *svm)
> +{
> +        unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
> +	struct vmcb *vmcb = svm->vmcb;

Nit: indentation

> +
> +	GUEST_ASSERT(svm->vmcb_gpa);
> +	/* Prepare for L2 execution. */
> +        generic_svm_setup(svm, svm_l2_guest_code,
> +                          &l2_guest_stack[L2_GUEST_STACK_SIZE]);
> +
> +	GUEST_SYNC(3);
> +	run_guest(vmcb, svm->vmcb_gpa);
> +	GUEST_ASSERT(vmcb->control.exit_code == SVM_EXIT_VMMCALL);
> +	GUEST_SYNC(5);
> +	vmcb->save.rip += 3;
> +	run_guest(vmcb, svm->vmcb_gpa);
> +	GUEST_ASSERT(vmcb->control.exit_code == SVM_EXIT_VMMCALL);
> +	GUEST_SYNC(7);
> +}
>  
> -void l2_guest_code(void)
> +void vmx_l2_guest_code(void)
>  {
>  	GUEST_SYNC(6);
>  
> @@ -42,9 +74,8 @@ void l2_guest_code(void)
>  	vmcall();
>  }
>  
> -void l1_guest_code(struct vmx_pages *vmx_pages)
> +static void vmx_l1_guest_code(struct vmx_pages *vmx_pages)
>  {
> -#define L2_GUEST_STACK_SIZE 64
>          unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
>  
>  	GUEST_ASSERT(vmx_pages->vmcs_gpa);
> @@ -56,7 +87,7 @@ void l1_guest_code(struct vmx_pages *vmx_pages)
>  	GUEST_SYNC(4);
>  	GUEST_ASSERT(vmptrstz() == vmx_pages->vmcs_gpa);
>  
> -	prepare_vmcs(vmx_pages, l2_guest_code,
> +	prepare_vmcs(vmx_pages, vmx_l2_guest_code,
>  		     &l2_guest_stack[L2_GUEST_STACK_SIZE]);
>  
>  	GUEST_SYNC(5);
> @@ -106,20 +137,31 @@ void l1_guest_code(struct vmx_pages *vmx_pages)
>  	GUEST_ASSERT(vmresume());
>  }
>  
> -void guest_code(struct vmx_pages *vmx_pages)
> +static u32 cpuid_ecx(u32 eax)
> +{
> +	u32 result;
> +	asm volatile("cpuid" : "=c" (result) : "a" (eax));

Nit: doesn't cpuid clobber ebx/edx too? (and ecx also works as
input). I'd suggest we write correct implementation and put it to
the library (or find a way to use native_cpuid() from
arch/x86/include/asm/processor.h)

> +	return result;
> +}
> +
> +static void __attribute__((__flatten__)) guest_code(void *arg)
>  {
>  	GUEST_SYNC(1);
>  	GUEST_SYNC(2);
>  
> -	if (vmx_pages)
> -		l1_guest_code(vmx_pages);
> +	if (arg) {
> +		if (cpuid_ecx(0x80000001) & CPUID_SVM)
> +			svm_l1_guest_code(arg);
> +		else
> +			vmx_l1_guest_code(arg);
> +	}
>  
>  	GUEST_DONE();
>  }
>  
>  int main(int argc, char *argv[])
>  {
> -	vm_vaddr_t vmx_pages_gva = 0;
> +	vm_vaddr_t nested_gva = 0;
>  
>  	struct kvm_regs regs1, regs2;
>  	struct kvm_vm *vm;
> @@ -136,8 +178,11 @@ int main(int argc, char *argv[])
>  	vcpu_regs_get(vm, VCPU_ID, &regs1);
>  
>  	if (kvm_check_cap(KVM_CAP_NESTED_STATE)) {
> -		vcpu_alloc_vmx(vm, &vmx_pages_gva);
> -		vcpu_args_set(vm, VCPU_ID, 1, vmx_pages_gva);
> +		if (kvm_get_supported_cpuid_entry(0x80000001)->ecx & CPUID_SVM)
> +			vcpu_alloc_svm(vm, &nested_gva);
> +		else
> +			vcpu_alloc_vmx(vm, &nested_gva);
> +		vcpu_args_set(vm, VCPU_ID, 1, nested_gva);
>  	} else {
>  		pr_info("will skip nested state checks\n");
>  		vcpu_args_set(vm, VCPU_ID, 1, 0);

With two nitpicks above,

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly