Re: [PATCH 1/2] eal: introduce x86 processor identification

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Sep 22, 2023 at 11:37:20AM +0200, David Marchand wrote:
> In some really specific cases, it may be needed to get a detailed
> information on the processor running a DPDK application for drivers to
> achieve better performance, or for matters that concern only them.
> 
> Those information are highly arch-specific and require a specific API.
> 
> Introduce a set of functions to get brand, family and model of a x86
> processor.
> Those functions do not make sense on other arches and a
> driver must first check rte_cpu_is_x86() before anything else.
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>  MAINTAINERS                     |   1 +
>  app/test/meson.build            |   1 +
>  app/test/test_cpu.c             |  37 +++++++++
>  lib/eal/common/eal_common_cpu.c | 141 ++++++++++++++++++++++++++++++++
>  lib/eal/common/eal_cpu.h        |  77 +++++++++++++++++
>  lib/eal/common/meson.build      |   1 +
>  lib/eal/version.map             |   6 ++
>  7 files changed, 264 insertions(+)
>  create mode 100644 app/test/test_cpu.c
>  create mode 100644 lib/eal/common/eal_common_cpu.c
>  create mode 100644 lib/eal/common/eal_cpu.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 698608cdb2..b87d47a1e4 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -158,6 +158,7 @@ F: app/test/test_barrier.c
>  F: app/test/test_bitcount.c
>  F: app/test/test_byteorder.c
>  F: app/test/test_common.c
> +F: app/test/test_cpu.c
>  F: app/test/test_cpuflags.c
>  F: app/test/test_cycles.c
>  F: app/test/test_debug.c
> diff --git a/app/test/meson.build b/app/test/meson.build
> index 05bae9216d..4b37ad02fa 100644
> --- a/app/test/meson.build
> +++ b/app/test/meson.build
> @@ -44,6 +44,7 @@ source_file_deps = {
>      'test_cmdline_string.c': [],
>      'test_common.c': [],
>      'test_compressdev.c': ['compressdev'],
> +    'test_cpu.c': [],
>      'test_cpuflags.c': [],
>      'test_crc.c': ['net'],
>      'test_cryptodev.c': test_cryptodev_deps,
> diff --git a/app/test/test_cpu.c b/app/test/test_cpu.c
> new file mode 100644
> index 0000000000..40d8bd94eb
> --- /dev/null
> +++ b/app/test/test_cpu.c
> @@ -0,0 +1,37 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2023 Red Hat, Inc.
> + */
> +
> +#include <stdio.h>
> +#include <inttypes.h>
> +
> +#include "eal_cpu.h"
> +
> +#include "test.h"
> +
> +static int
> +test_cpu(void)
> +{
> +#ifndef RTE_ARCH_X86
> +	RTE_TEST_ASSERT(!rte_cpu_is_x86(), "rte_cpu_is_x86() returned true on " RTE_STR(RTE_ARCH));
> +#else
> +	const char *vendor;
> +
> +	RTE_TEST_ASSERT(rte_cpu_is_x86(), "rte_cpu_is_x86() returned false");
> +
> +	if (rte_cpu_x86_is_amd())
> +		vendor = "AMD";
> +	else if (rte_cpu_x86_is_intel())
> +		vendor = "Intel";
> +	else
> +		vendor = "unknown";
> +
> +	printf("The processor running this program is a x86 %s processor, brand=0x%"
> +		PRIx8", family=0x%"PRIx8", model=0x%"PRIx8"\n", vendor, rte_cpu_x86_brand(),
> +		rte_cpu_x86_family(), rte_cpu_x86_model());
> +#endif
> +
> +	return TEST_SUCCESS;
> +}
> +
> +REGISTER_FAST_TEST(cpu_autotest, true, true, test_cpu);
> diff --git a/lib/eal/common/eal_common_cpu.c b/lib/eal/common/eal_common_cpu.c
> new file mode 100644
> index 0000000000..18cdb27f75
> --- /dev/null
> +++ b/lib/eal/common/eal_common_cpu.c
> @@ -0,0 +1,141 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2023 Red Hat, Inc.
> + */
> +
> +#include <rte_debug.h>
> +
> +#include "eal_cpu.h"
> +
> +#ifdef RTE_ARCH_X86
> +#ifndef RTE_TOOLCHAIN_MSVC
> +#include <cpuid.h>
> +#endif
> +
> +static void
> +x86_cpuid(uint32_t leaf, uint32_t subleaf, uint32_t *eax, uint32_t *ebx,
> +	uint32_t *ecx, uint32_t *edx)
> +{
> +	uint32_t regs[4] = { 0 };
> +
> +#ifdef RTE_TOOLCHAIN_MSVC
> +	__cpuidex(regs, leaf, subleaf);
> +#else
> +	__cpuid_count(leaf, subleaf, regs[0], regs[1], regs[2], regs[3]);
> +#endif
> +
> +	*eax = regs[0];
> +	*ebx = regs[1];
> +	*ecx = regs[2];
> +	*edx = regs[3];
> +}
> +#endif /* RTE_ARCH_X86 */

From a readability perspective, I think it would be better to expand the
scope of this ifdef and have two copies of each function in the file,
rather than a single copy of each with #ifdefs. WDYT?

/Bruce