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
cda64169ba