+static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning);
+static unsigned long cr4_pinned_bits __ro_after_init;
+
+void native_write_cr0(unsigned long val)
+{
+ unsigned long bits_missing = 0;
+
+set_register:
+ asm volatile("mov %0,%%cr0": "+r" (val), "+m" (__force_order));
+
+ if (static_branch_likely(&cr_pinning)) {
+ if (unlikely((val & X86_CR0_WP) != X86_CR0_WP)) {
+ bits_missing = X86_CR0_WP;
+ val |= bits_missing;
+ goto set_register;
+ }
+ /* Warn after we've set the missing bits. */
+ WARN_ONCE(bits_missing, "CR0 WP bit went missing!?\n");
+ }
+}
+EXPORT_SYMBOL(native_write_cr0);
+
+void native_write_cr4(unsigned long val)
+{
+ unsigned long bits_missing = 0;
+
+set_register:
+ asm volatile("mov %0,%%cr4": "+r" (val), "+m" (cr4_pinned_bits));
+
+ if (static_branch_likely(&cr_pinning)) {
+ if (unlikely((val & cr4_pinned_bits) != cr4_pinned_bits)) {
+ bits_missing = ~val & cr4_pinned_bits;
+ val |= bits_missing;
+ goto set_register;
+ }
+ /* Warn after we've set the missing bits. */
+ WARN_ONCE(bits_missing, "CR4 bits went missing: %lx!?\n",
+ bits_missing);
+ }
+}
+EXPORT_SYMBOL(native_write_cr4);
+
+void cr4_init(void)
+{
+ unsigned long cr4 = __read_cr4();
+
+ if (boot_cpu_has(X86_FEATURE_PCID))
+ cr4 |= X86_CR4_PCIDE;
+ if (static_branch_likely(&cr_pinning))
+ cr4 |= cr4_pinned_bits;
+
+ __write_cr4(cr4);
+
+ /* Initialize cr4 shadow for this CPU. */
+ this_cpu_write(cpu_tlbstate.cr4, cr4);
+}