linux-kernel - Re: [PATCH v2 14/49] KVM: selftests: Update x86's KVM PV test to match KVM's disabling exits behavior

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Message-ID: <7a2ff05bfa3f9a2c9b71ac5fbfd75ef50f0bbf9e.camel@redhat.com>
Date: Thu, 04 Jul 2024 21:17:29 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>,  Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, Hou Wenlong
 <houwenlong.hwl@...group.com>, Kechen Lu <kechenl@...dia.com>, Oliver Upton
 <oliver.upton@...ux.dev>, Binbin Wu <binbin.wu@...ux.intel.com>, Yang
 Weijiang <weijiang.yang@...el.com>, Robert Hoo <robert.hoo.linux@...il.com>
Subject: Re: [PATCH v2 14/49] KVM: selftests: Update x86's KVM PV test to
 match KVM's disabling exits behavior

On Fri, 2024-05-17 at 10:38 -0700, Sean Christopherson wrote:
> Rework x86's KVM PV features test to align with KVM's new, fixed behavior
> of not allowing userspace to disable HLT-exiting after vCPUs have been
> created.  Rework the core testcase to disable HLT-exiting before creating
> a vCPU, and opportunistically modify keep the paired VM+vCPU creation to
> verify that KVM rejects KVM_CAP_X86_DISABLE_EXITS as expected.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  .../selftests/kvm/x86_64/kvm_pv_test.c        | 33 +++++++++++++++++--
>  1 file changed, 30 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
> index 2aee93108a54..1b805cbdb47b 100644
> --- a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
> @@ -139,6 +139,7 @@ static void test_pv_unhalt(void)
>  	struct kvm_vm *vm;
>  	struct kvm_cpuid_entry2 *ent;
>  	u32 kvm_sig_old;
> +	int r;
>  
>  	if (!(kvm_check_cap(KVM_CAP_X86_DISABLE_EXITS) & KVM_X86_DISABLE_EXITS_HLT))
>  		return;
> @@ -152,19 +153,45 @@ static void test_pv_unhalt(void)
>  	TEST_ASSERT(vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
>  		    "Enabling X86_FEATURE_KVM_PV_UNHALT had no effect");
>  
> -	/* Make sure KVM clears vcpu->arch.kvm_cpuid */
> +	/* Verify KVM disallows disabling exits after vCPU creation. */
> +	r = __vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, KVM_X86_DISABLE_EXITS_HLT);
> +	TEST_ASSERT(r && errno == EINVAL,
> +		    "Disabling exits after vCPU creation didn't fail as expected");
> +
> +	kvm_vm_free(vm);
> +
> +	/* Verify that KVM clear PV_UNHALT from guest CPUID. */
> +	vm = vm_create(1);
> +	vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, KVM_X86_DISABLE_EXITS_HLT);
> +
> +	vcpu = vm_vcpu_add(vm, 0, NULL);
> +	TEST_ASSERT(!vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
> +		    "vCPU created with PV_UNHALT set by default");
> +
> +	vcpu_set_cpuid_feature(vcpu, X86_FEATURE_KVM_PV_UNHALT);
> +	TEST_ASSERT(!vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
> +		    "PV_UNHALT set in guest CPUID when HLT-exiting is disabled");
> +
> +	/*
> +	 * Clobber the KVM PV signature and verify KVM does NOT clear PV_UNHALT
> +	 * when KVM PV is not present, and DOES clear PV_UNHALT when switching
> +	 * back to the correct signature..
> +	 */
>  	ent = vcpu_get_cpuid_entry(vcpu, KVM_CPUID_SIGNATURE);
>  	kvm_sig_old = ent->ebx;
>  	ent->ebx = 0xdeadbeef;
>  	vcpu_set_cpuid(vcpu);
>  
> -	vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, KVM_X86_DISABLE_EXITS_HLT);
> +	vcpu_set_cpuid_feature(vcpu, X86_FEATURE_KVM_PV_UNHALT);
> +	TEST_ASSERT(vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
> +		    "PV_UNHALT cleared when using bogus KVM PV signature");
> +
>  	ent = vcpu_get_cpuid_entry(vcpu, KVM_CPUID_SIGNATURE);
>  	ent->ebx = kvm_sig_old;
>  	vcpu_set_cpuid(vcpu);
>  
>  	TEST_ASSERT(!vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
> -		    "KVM_FEATURE_PV_UNHALT is set with KVM_CAP_X86_DISABLE_EXITS");
> +		    "PV_UNHALT set in guest CPUID when HLT-exiting is disabled");
>  
>  	/* FIXME: actually test KVM_FEATURE_PV_UNHALT feature */
>  

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

Best regards,
	Maxim Levitsky