Merge tag 'x86-entry-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git...

[linux-2.6-microblaze.git] / arch / x86 / entry / calling.h

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 3ff925b..1c3b561 100644 (file)
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -244,17 +244,19 @@ For 32-bit we have the following conventions - kernel is built with
 .Ldone_\@:
 .endm
 
-.macro RESTORE_CR3 scratch_reg:req save_reg:req
+/* Restore CR3 from a kernel context. May restore a user CR3 value. */
+.macro PARANOID_RESTORE_CR3 scratch_reg:req save_reg:req
        ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
 
-       ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID
-
        /*
-        * KERNEL pages can always resume with NOFLUSH as we do
-        * explicit flushes.
+        * If CR3 contained the kernel page tables at the paranoid exception
+        * entry, then there is nothing to restore as CR3 is not modified while
+        * handling the exception.
         */
        bt      $PTI_USER_PGTABLE_BIT, \save_reg
-       jnc     .Lnoflush_\@
+       jnc     .Lend_\@
+
+       ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID
 
        /*
         * Check if there's a pending flush for the user ASID we're
@@ -262,20 +264,12 @@ For 32-bit we have the following conventions - kernel is built with
         */
        movq    \save_reg, \scratch_reg
        andq    $(0x7FF), \scratch_reg
-       bt      \scratch_reg, THIS_CPU_user_pcid_flush_mask
-       jnc     .Lnoflush_\@
-
        btr     \scratch_reg, THIS_CPU_user_pcid_flush_mask
-       jmp     .Lwrcr3_\@
+       jc      .Lwrcr3_\@
 
-.Lnoflush_\@:
        SET_NOFLUSH_BIT \save_reg
 
 .Lwrcr3_\@:
-       /*
-        * The CR3 write could be avoided when not changing its value,
-        * but would require a CR3 read *and* a scratch register.
-        */
        movq    \save_reg, %cr3
 .Lend_\@:
 .endm
@@ -290,7 +284,7 @@ For 32-bit we have the following conventions - kernel is built with
 .endm
 .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
 .endm
-.macro RESTORE_CR3 scratch_reg:req save_reg:req
+.macro PARANOID_RESTORE_CR3 scratch_reg:req save_reg:req
 .endm
 
 #endif