linux/arch/x86/kernel/cpu/cpuid-deps.c

/* Declare dependencies between CPUIDs */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <asm/cpufeature.h>

struct cpuid_dep {
	unsigned int	feature;
	unsigned int	depends;
};

/*
 * Table of CPUID features that depend on others.
 *
 * This only includes dependencies that can be usefully disabled, not
 * features part of the base set (like FPU).
 *
 * Note this all is not __init / __initdata because it can be
 * called from cpu hotplug. It shouldn't do anything in this case,
 * but it's difficult to tell that to the init reference checker.
 */
static const struct cpuid_dep cpuid_deps[] = {
	{ X86_FEATURE_FXSR,			X86_FEATURE_FPU	      },
	{ X86_FEATURE_XSAVEOPT,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_XSAVEC,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_XSAVES,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_AVX,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_PKU,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_MPX,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_XGETBV1,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_APX,			X86_FEATURE_XSAVE     },
	{ X86_FEATURE_CMOV,			X86_FEATURE_FXSR      },
	{ X86_FEATURE_MMX,			X86_FEATURE_FXSR      },
	{ X86_FEATURE_MMXEXT,			X86_FEATURE_MMX       },
	{ X86_FEATURE_FXSR_OPT,			X86_FEATURE_FXSR      },
	{ X86_FEATURE_XSAVE,			X86_FEATURE_FXSR      },
	{ X86_FEATURE_XMM,			X86_FEATURE_FXSR      },
	{ X86_FEATURE_XMM2,			X86_FEATURE_XMM       },
	{ X86_FEATURE_XMM3,			X86_FEATURE_XMM2      },
	{ X86_FEATURE_XMM4_1,			X86_FEATURE_XMM2      },
	{ X86_FEATURE_XMM4_2,			X86_FEATURE_XMM2      },
	{ X86_FEATURE_XMM3,			X86_FEATURE_XMM2      },
	{ X86_FEATURE_PCLMULQDQ,		X86_FEATURE_XMM2      },
	{ X86_FEATURE_SSSE3,			X86_FEATURE_XMM2,     },
	{ X86_FEATURE_F16C,			X86_FEATURE_XMM2,     },
	{ X86_FEATURE_AES,			X86_FEATURE_XMM2      },
	{ X86_FEATURE_SHA_NI,			X86_FEATURE_XMM2      },
	{ X86_FEATURE_GFNI,			X86_FEATURE_XMM2      },
	{ X86_FEATURE_AVX_VNNI,			X86_FEATURE_AVX       },
	{ X86_FEATURE_FMA,			X86_FEATURE_AVX       },
	{ X86_FEATURE_VAES,			X86_FEATURE_AVX       },
	{ X86_FEATURE_VPCLMULQDQ,		X86_FEATURE_AVX       },
	{ X86_FEATURE_AVX2,			X86_FEATURE_AVX,      },
	{ X86_FEATURE_AVX512F,			X86_FEATURE_AVX,      },
	{ X86_FEATURE_AVX512IFMA,		X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512PF,			X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512ER,			X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512CD,			X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512DQ,			X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512BW,			X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512VL,			X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512VBMI,		X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512_VBMI2,		X86_FEATURE_AVX512VL  },
	{ X86_FEATURE_AVX512_VNNI,		X86_FEATURE_AVX512VL  },
	{ X86_FEATURE_AVX512_BITALG,		X86_FEATURE_AVX512VL  },
	{ X86_FEATURE_AVX512_4VNNIW,		X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512_4FMAPS,		X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512_VPOPCNTDQ,		X86_FEATURE_AVX512F   },
	{ X86_FEATURE_AVX512_VP2INTERSECT,	X86_FEATURE_AVX512VL  },
	{ X86_FEATURE_CQM_OCCUP_LLC,		X86_FEATURE_CQM_LLC   },
	{ X86_FEATURE_CQM_MBM_TOTAL,		X86_FEATURE_CQM_LLC   },
	{ X86_FEATURE_CQM_MBM_LOCAL,		X86_FEATURE_CQM_LLC   },
	{ X86_FEATURE_BMEC,			X86_FEATURE_CQM_MBM_TOTAL   },
	{ X86_FEATURE_BMEC,			X86_FEATURE_CQM_MBM_LOCAL   },
	{ X86_FEATURE_AVX512_BF16,		X86_FEATURE_AVX512VL  },
	{ X86_FEATURE_AVX512_FP16,		X86_FEATURE_AVX512BW  },
	{ X86_FEATURE_ENQCMD,			X86_FEATURE_XSAVES    },
	{ X86_FEATURE_PER_THREAD_MBA,		X86_FEATURE_MBA       },
	{ X86_FEATURE_SGX_LC,			X86_FEATURE_SGX	      },
	{ X86_FEATURE_SGX1,			X86_FEATURE_SGX       },
	{ X86_FEATURE_SGX2,			X86_FEATURE_SGX1      },
	{ X86_FEATURE_SGX_EDECCSSA,		X86_FEATURE_SGX1      },
	{ X86_FEATURE_XFD,			X86_FEATURE_XSAVES    },
	{ X86_FEATURE_XFD,			X86_FEATURE_XGETBV1   },
	{ X86_FEATURE_AMX_TILE,			X86_FEATURE_XFD       },
	{ X86_FEATURE_AMX_FP16,			X86_FEATURE_AMX_TILE  },
	{ X86_FEATURE_AMX_BF16,			X86_FEATURE_AMX_TILE  },
	{ X86_FEATURE_AMX_INT8,			X86_FEATURE_AMX_TILE  },
	{ X86_FEATURE_SHSTK,			X86_FEATURE_XSAVES    },
	{ X86_FEATURE_FRED,			X86_FEATURE_LKGS      },
	{ X86_FEATURE_SPEC_CTRL_SSBD,		X86_FEATURE_SPEC_CTRL },
	{}
};

static inline void clear_feature(struct cpuinfo_x86 *c, unsigned int feature)
{
	/*
	 * Note: This could use the non atomic __*_bit() variants, but the
	 * rest of the cpufeature code uses atomics as well, so keep it for
	 * consistency. Cleanup all of it separately.
	 */
	if (!c) {
		clear_cpu_cap(&boot_cpu_data, feature);
		set_bit(feature, (unsigned long *)cpu_caps_cleared);
	} else {
		clear_bit(feature, (unsigned long *)c->x86_capability);
	}
}

/* Take the capabilities and the BUG bits into account */
#define MAX_FEATURE_BITS ((NCAPINTS + NBUGINTS) * sizeof(u32) * 8)

static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
{
	DECLARE_BITMAP(disable, MAX_FEATURE_BITS);
	const struct cpuid_dep *d;
	bool changed;

	if (WARN_ON(feature >= MAX_FEATURE_BITS))
		return;

	if (boot_cpu_has(feature))
		WARN_ON(alternatives_patched);

	clear_feature(c, feature);

	/* Collect all features to disable, handling dependencies */
	memset(disable, 0, sizeof(disable));
	__set_bit(feature, disable);

	/* Loop until we get a stable state. */
	do {
		changed = false;
		for (d = cpuid_deps; d->feature; d++) {
			if (!test_bit(d->depends, disable))
				continue;
			if (__test_and_set_bit(d->feature, disable))
				continue;

			changed = true;
			clear_feature(c, d->feature);
		}
	} while (changed);
}

void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
{
	do_clear_cpu_cap(c, feature);
}

void setup_clear_cpu_cap(unsigned int feature)
{
	do_clear_cpu_cap(NULL, feature);
}

/*
 * Return the feature "name" if available, otherwise return
 * the X86_FEATURE_* numerals to make it easier to identify
 * the feature.
 */
static const char *x86_feature_name(unsigned int feature, char *buf)
{
	if (x86_cap_flags[feature])
		return x86_cap_flags[feature];

	snprintf(buf, 16, "%d*32+%2d", feature / 32, feature % 32);

	return buf;
}

void check_cpufeature_deps(struct cpuinfo_x86 *c)
{
	char feature_buf[16], depends_buf[16];
	const struct cpuid_dep *d;

	for (d = cpuid_deps; d->feature; d++) {
		if (cpu_has(c, d->feature) && !cpu_has(c, d->depends)) {
			/*
			 * Only warn about the first unmet dependency on the
			 * first CPU where it is encountered to avoid spamming
			 * the kernel log.
			 */
			pr_warn_once("x86 CPU feature dependency check failure: CPU%d has '%s' enabled but '%s' disabled. Kernel might be fine, but no guarantees.\n",
				     smp_processor_id(),
				     x86_feature_name(d->feature, feature_buf),
				     x86_feature_name(d->depends, depends_buf));
		}
	}
}