linux-kernel - Re: [PATCH] KVM: selftests: Add coverage of MTE system registers

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Message-ID: <87edpu5klk.wl-maz@kernel.org>
Date:   Sun, 12 Mar 2023 10:29:11 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: selftests: Add coverage of MTE system registers

On Wed, 08 Mar 2023 17:12:26 +0000,
Mark Brown <broonie@...nel.org> wrote:
> 
> Verify that a guest with MTE has access to the MTE registers. Since MTE is
> enabled as a VM wide capability we need to add support for doing that in
> the process.
> 
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  tools/testing/selftests/kvm/aarch64/get-reg-list.c | 33 ++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/aarch64/get-reg-list.c b/tools/testing/selftests/kvm/aarch64/get-reg-list.c
> index d287dd2cac0a..63d6a9046702 100644
> --- a/tools/testing/selftests/kvm/aarch64/get-reg-list.c
> +++ b/tools/testing/selftests/kvm/aarch64/get-reg-list.c
> @@ -42,6 +42,7 @@ struct reg_sublist {
>  	long capability;
>  	int feature;
>  	bool finalize;
> +	bool enable_capability;
>  	__u64 *regs;
>  	__u64 regs_n;
>  	__u64 *rejects_set;
> @@ -404,6 +405,18 @@ static void check_supported(struct vcpu_config *c)
>  	}
>  }
>  
> +static void enable_capabilities(struct kvm_vm *vm, struct vcpu_config *c)
> +{
> +	struct reg_sublist *s;
> +
> +	for_each_sublist(c, s) {
> +		if (!s->enable_capability)
> +			continue;
> +
> +		vm_enable_cap(vm, s->capability, 1);
> +	}
> +}
> +
>  static bool print_list;
>  static bool print_filtered;
>  static bool fixup_core_regs;
> @@ -420,6 +433,7 @@ static void run_test(struct vcpu_config *c)
>  	check_supported(c);
>  
>  	vm = vm_create_barebones();
> +	enable_capabilities(vm, c);
>  	prepare_vcpu_init(c, &init);
>  	vcpu = __vm_vcpu_add(vm, 0);
>  	aarch64_vcpu_setup(vcpu, &init);
> @@ -1049,6 +1063,13 @@ static __u64 pauth_generic_regs[] = {
>  	ARM64_SYS_REG(3, 0, 2, 3, 1),	/* APGAKEYHI_EL1 */
>  };
>  
> +static __u64 mte_regs[] = {
> +	ARM64_SYS_REG(3, 0, 1, 0, 5),	/* RGSR_EL1 */
> +	ARM64_SYS_REG(3, 0, 1, 0, 6),	/* GCR_EL1 */
> +	ARM64_SYS_REG(3, 0, 5, 6, 0),	/* TFSR_EL1 */
> +	ARM64_SYS_REG(3, 0, 5, 6, 1),	/* TFSRE0_EL1 */
> +};
> +
>  #define BASE_SUBLIST \
>  	{ "base", .regs = base_regs, .regs_n = ARRAY_SIZE(base_regs), }
>  #define VREGS_SUBLIST \
> @@ -1075,6 +1096,9 @@ static __u64 pauth_generic_regs[] = {
>  		.regs		= pauth_generic_regs,			\
>  		.regs_n		= ARRAY_SIZE(pauth_generic_regs),	\
>  	}
> +#define MTE_SUBLIST \
> +	{ "mte", .capability = KVM_CAP_ARM_MTE, .enable_capability = true,  \
> +	  .regs = mte_regs, .regs_n = ARRAY_SIZE(mte_regs), }
>  
>  static struct vcpu_config vregs_config = {
>  	.sublists = {
> @@ -1123,6 +1147,14 @@ static struct vcpu_config pauth_pmu_config = {
>  	{0},
>  	},
>  };
> +static struct vcpu_config mte_config = {
> +	.sublists = {
> +	BASE_SUBLIST,
> +	VREGS_SUBLIST,
> +	MTE_SUBLIST,
> +	{0},
> +	},
> +};
>  
>  static struct vcpu_config *vcpu_configs[] = {
>  	&vregs_config,
> @@ -1131,5 +1163,6 @@ static struct vcpu_config *vcpu_configs[] = {
>  	&sve_pmu_config,
>  	&pauth_config,
>  	&pauth_pmu_config,
> +	&mte_config,
>  };
>  static int vcpu_configs_n = ARRAY_SIZE(vcpu_configs);
> 

Is there any reason why we sidestep the combinations of MTE with PAuth
and PMU? I know this leads to an exponential set growth, but this is
the very purpose of this test, and we found bugs related to this in
the past.

A good first step would be to be able to build these combinations
dynamically, and only then add new sublists to the mix.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.