Files
linux/arch/x86/kernel/cpu/microcode/internal.h
Borislav Petkov cda64169ba x86/microcode: Do not access MSR_IA32_PLATFORM_ID when running as a guest
Patch in Fixes: causes the usual:

  unchecked MSR access error: RDMSR from 0x17 at ... (intel_get_platform_id)
  Call Trace:
   early_init_intel
   early_cpu_init
   setup_arch
   _printk
   start_kernel
   x86_64_start_reservations
   x86_64_start_kernel
   common_startup_64

because the kernel is booted in a guest.

In order to avoid it, this MSR access needs to be prevented when running
virtualized. That is usually done by checking X86_FEATURE_HYPERVISOR but
for this particular case it is too early yet.

The platform ID needs to be read as early as when microcode is loaded on
the BSP:

  load_ucode_bsp ... -> get_microcode_blob ... -> intel_find_matching_signature

and by that time, CPUID leafs haven't been parsed yet.

The microcode loader already has logic to check early whether the kernel
is running virtualized so make that globally available to arch/x86/. The
query whether running virtualized is getting more and more prominent in
recent times so might as well make it an arch-global var which the rest
of the code can use.

Fixes: d8630b67ca ("x86/cpu: Add platform ID to CPU info structure")
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Tested-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/all/20260430020953.1405535-1-binbin.wu@linux.intel.com
2026-05-26 13:36:23 -07:00

137 lines
3.9 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _X86_MICROCODE_INTERNAL_H
#define _X86_MICROCODE_INTERNAL_H
#include <linux/earlycpio.h>
#include <linux/initrd.h>
#include <asm/cpu.h>
#include <asm/microcode.h>
struct device;
enum ucode_state {
UCODE_OK = 0,
UCODE_NEW,
UCODE_NEW_SAFE,
UCODE_UPDATED,
UCODE_NFOUND,
UCODE_ERROR,
UCODE_TIMEOUT,
UCODE_OFFLINE,
};
struct microcode_ops {
enum ucode_state (*request_microcode_fw)(int cpu, struct device *dev);
void (*microcode_fini_cpu)(int cpu);
/*
* The generic 'microcode_core' part guarantees that the callbacks
* below run on a target CPU when they are being called.
* See also the "Synchronization" section in microcode_core.c.
*/
enum ucode_state (*apply_microcode)(int cpu);
void (*stage_microcode)(void);
int (*collect_cpu_info)(int cpu, struct cpu_signature *csig);
void (*finalize_late_load)(int result);
unsigned int nmi_safe : 1,
use_nmi : 1,
use_staging : 1;
};
struct early_load_data {
u32 old_rev;
u32 new_rev;
};
extern struct early_load_data early_data;
extern struct ucode_cpu_info ucode_cpu_info[];
extern u32 microcode_rev[NR_CPUS];
extern u32 base_rev;
struct cpio_data find_microcode_in_initrd(const char *path);
#define MAX_UCODE_COUNT 128
#define QCHAR(a, b, c, d) ((a) + ((b) << 8) + ((c) << 16) + ((d) << 24))
#define CPUID_INTEL1 QCHAR('G', 'e', 'n', 'u')
#define CPUID_INTEL2 QCHAR('i', 'n', 'e', 'I')
#define CPUID_INTEL3 QCHAR('n', 't', 'e', 'l')
#define CPUID_AMD1 QCHAR('A', 'u', 't', 'h')
#define CPUID_AMD2 QCHAR('e', 'n', 't', 'i')
#define CPUID_AMD3 QCHAR('c', 'A', 'M', 'D')
#define CPUID_IS(a, b, c, ebx, ecx, edx) \
(!(((ebx) ^ (a)) | ((edx) ^ (b)) | ((ecx) ^ (c))))
/*
* In early loading microcode phase on BSP, boot_cpu_data is not set up yet.
* x86_cpuid_vendor() gets vendor id for BSP.
*
* In 32 bit AP case, accessing boot_cpu_data needs linear address. To simplify
* coding, we still use x86_cpuid_vendor() to get vendor id for AP.
*
* x86_cpuid_vendor() gets vendor information directly from CPUID.
*/
static inline int x86_cpuid_vendor(void)
{
u32 eax = 0x00000000;
u32 ebx, ecx = 0, edx;
native_cpuid(&eax, &ebx, &ecx, &edx);
if (CPUID_IS(CPUID_INTEL1, CPUID_INTEL2, CPUID_INTEL3, ebx, ecx, edx))
return X86_VENDOR_INTEL;
if (CPUID_IS(CPUID_AMD1, CPUID_AMD2, CPUID_AMD3, ebx, ecx, edx))
return X86_VENDOR_AMD;
return X86_VENDOR_UNKNOWN;
}
static inline unsigned int x86_cpuid_family(void)
{
u32 eax = 0x00000001;
u32 ebx, ecx = 0, edx;
native_cpuid(&eax, &ebx, &ecx, &edx);
return x86_family(eax);
}
extern bool force_minrev;
#ifdef CONFIG_CPU_SUP_AMD
void load_ucode_amd_bsp(struct early_load_data *ed, unsigned int family);
void load_ucode_amd_ap(unsigned int family);
void reload_ucode_amd(unsigned int cpu);
struct microcode_ops *init_amd_microcode(void);
void exit_amd_microcode(void);
#else /* CONFIG_CPU_SUP_AMD */
static inline void load_ucode_amd_bsp(struct early_load_data *ed, unsigned int family) { }
static inline void load_ucode_amd_ap(unsigned int family) { }
static inline void reload_ucode_amd(unsigned int cpu) { }
static inline struct microcode_ops *init_amd_microcode(void) { return NULL; }
static inline void exit_amd_microcode(void) { }
#endif /* !CONFIG_CPU_SUP_AMD */
#ifdef CONFIG_CPU_SUP_INTEL
void load_ucode_intel_bsp(struct early_load_data *ed);
void load_ucode_intel_ap(void);
void reload_ucode_intel(void);
struct microcode_ops *init_intel_microcode(void);
#else /* CONFIG_CPU_SUP_INTEL */
static inline void load_ucode_intel_bsp(struct early_load_data *ed) { }
static inline void load_ucode_intel_ap(void) { }
static inline void reload_ucode_intel(void) { }
static inline struct microcode_ops *init_intel_microcode(void) { return NULL; }
#endif /* !CONFIG_CPU_SUP_INTEL */
#define ucode_dbg(fmt, ...) \
({ \
if (IS_ENABLED(CONFIG_MICROCODE_DBG)) \
pr_info(fmt, ##__VA_ARGS__); \
})
#endif /* _X86_MICROCODE_INTERNAL_H */