Re: [PATCH v2 1/9] KVM: arm64: selftests: Use FIELD_GET() to extract ID register fields

From: Oliver Upton <oliver.upton@linux.dev>
To: Reiji Watanabe <reijiw@google.com>
Cc: Marc Zyngier <maz@kernel.org>,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Andrew Jones <andrew.jones@linux.dev>,
	Ricardo Koller <ricarkol@google.com>,
	Jing Zhang <jingzhangos@google.com>,
	Raghavendra Rao Anata <rananta@google.com>
Subject: Re: [PATCH v2 1/9] KVM: arm64: selftests: Use FIELD_GET() to extract ID register fields
Date: Thu, 20 Oct 2022 22:08:00 +0300	[thread overview]
Message-ID: <Y1GckDU/gCNQ6tAS@google.com> (raw)
In-Reply-To: <20221020054202.2119018-2-reijiw@google.com>

On Wed, Oct 19, 2022 at 10:41:54PM -0700, Reiji Watanabe wrote:
> Use FIELD_GET() macro to extract ID register fields for existing
> aarch64 selftests code. No functional change intended.
> 
> Signed-off-by: Reiji Watanabe <reijiw@google.com>
> ---
>  tools/testing/selftests/kvm/aarch64/aarch32_id_regs.c  | 3 ++-
>  tools/testing/selftests/kvm/aarch64/debug-exceptions.c | 3 ++-
>  tools/testing/selftests/kvm/lib/aarch64/processor.c    | 7 ++++---
>  3 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/aarch64/aarch32_id_regs.c b/tools/testing/selftests/kvm/aarch64/aarch32_id_regs.c
> index 6f9c1f19c7f6..b6a5e8861b35 100644
> --- a/tools/testing/selftests/kvm/aarch64/aarch32_id_regs.c
> +++ b/tools/testing/selftests/kvm/aarch64/aarch32_id_regs.c
> @@ -13,6 +13,7 @@
>  #include "kvm_util.h"
>  #include "processor.h"
>  #include "test_util.h"
> +#include <linux/bitfield.h>
>  
>  #define BAD_ID_REG_VAL	0x1badc0deul
>  
> @@ -145,7 +146,7 @@ static bool vcpu_aarch64_only(struct kvm_vcpu *vcpu)
>  
>  	vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_ID_AA64PFR0_EL1), &val);
>  
> -	el0 = (val & ARM64_FEATURE_MASK(ID_AA64PFR0_EL0)) >> ID_AA64PFR0_EL0_SHIFT;
> +	el0 = FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL0), val);
>  	return el0 == ID_AA64PFR0_ELx_64BIT_ONLY;
>  }
>  
> diff --git a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
> index 947bd201435c..3808d3d75055 100644
> --- a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
> +++ b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
> @@ -2,6 +2,7 @@
>  #include <test_util.h>
>  #include <kvm_util.h>
>  #include <processor.h>
> +#include <linux/bitfield.h>
>  
>  #define MDSCR_KDE	(1 << 13)
>  #define MDSCR_MDE	(1 << 15)
> @@ -284,7 +285,7 @@ static int debug_version(struct kvm_vcpu *vcpu)
>  	uint64_t id_aa64dfr0;
>  
>  	vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_ID_AA64DFR0_EL1), &id_aa64dfr0);
> -	return id_aa64dfr0 & 0xf;
> +	return FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER), id_aa64dfr0);
>  }
>  
>  static void test_guest_debug_exceptions(void)
> diff --git a/tools/testing/selftests/kvm/lib/aarch64/processor.c b/tools/testing/selftests/kvm/lib/aarch64/processor.c
> index 6f5551368944..7c96b931edd5 100644
> --- a/tools/testing/selftests/kvm/lib/aarch64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/aarch64/processor.c
> @@ -11,6 +11,7 @@
>  #include "guest_modes.h"
>  #include "kvm_util.h"
>  #include "processor.h"
> +#include <linux/bitfield.h>
>  
>  #define DEFAULT_ARM64_GUEST_STACK_VADDR_MIN	0xac0000
>  
> @@ -486,9 +487,9 @@ void aarch64_get_supported_page_sizes(uint32_t ipa,
>  	err = ioctl(vcpu_fd, KVM_GET_ONE_REG, &reg);
>  	TEST_ASSERT(err == 0, KVM_IOCTL_ERROR(KVM_GET_ONE_REG, vcpu_fd));
>  
> -	*ps4k = ((val >> 28) & 0xf) != 0xf;
> -	*ps64k = ((val >> 24) & 0xf) == 0;
> -	*ps16k = ((val >> 20) & 0xf) != 0;
> +	*ps4k = FIELD_GET(ARM64_FEATURE_MASK(ID_AA64MMFR0_TGRAN4), val) != 0xf;
> +	*ps64k = FIELD_GET(ARM64_FEATURE_MASK(ID_AA64MMFR0_TGRAN64), val) == 0;
> +	*ps16k = FIELD_GET(ARM64_FEATURE_MASK(ID_AA64MMFR0_TGRAN16), val) != 0;

Not your code, but since we're here...

Should we change the field values to use the #define's? Also, the test
for TGRAN64 looks wrong. We should test != ID_AA64MMFR0_TGRAN64_NI. A
value greater than 0 would indicate an extension of the feature.

But for this exact change:

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>