The condition for reading CR4 was wrong: there are some CPUs with CPUID but not CR4. Rather than trying to make the condition exact, using __read_cr4_safe().
Reported-by: [email protected] Fixes: 18bc7bd523e0 ("x86/boot: Synchronize trampoline_cr4_features and mmu_cr4_features directly") Signed-off-by: Andy Lutomirski <[email protected]> --- arch/x86/kernel/setup.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 0fa60f5f5a16..5930a4d191b4 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1137,9 +1137,13 @@ void __init setup_arch(char **cmdline_p) * auditing all the early-boot CR4 manipulation would be needed to * rule it out. */ - if (boot_cpu_data.cpuid_level >= 0) - /* A CPU has %cr4 if and only if it has CPUID. */ - mmu_cr4_features = __read_cr4(); + if (boot_cpu_data.cpuid_level >= 0) { + /* + * CPUs without CPUID don't have CR4. CPUs with CPUID + * usually have CR4. + */ + mmu_cr4_features = __read_cr4_safe(); + } memblock_set_current_limit(get_max_mapped()); -- 2.7.4
