diff options
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 40cb4d0a5982..fb1d3358a4af 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -333,6 +333,19 @@ static void setup_pcid(struct cpuinfo_x86 *c) { if (cpu_has(c, X86_FEATURE_PCID)) { if (cpu_has(c, X86_FEATURE_PGE)) { + /* + * We'd like to use cr4_set_bits_and_update_boot(), + * but we can't. CR4.PCIDE is special and can only + * be set in long mode, and the early CPU init code + * doesn't know this and would try to restore CR4.PCIDE + * prior to entering long mode. + * + * Instead, we rely on the fact that hotplug, resume, + * etc all fully restore CR4 before they write anything + * that could have nonzero PCID bits to CR3. CR4.PCIDE + * has no effect on the page tables themselves, so we + * don't need it to be restored early. + */ cr4_set_bits(X86_CR4_PCIDE); } else { /* |