Patch "kaiser: kaiser_flush_tlb_on_return_to_user() check PCID" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    kaiser: kaiser_flush_tlb_on_return_to_user() check PCID

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kaiser-kaiser_flush_tlb_on_return_to_user-check-pcid.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Jan  3 18:58:12 CET 2018
From: Hugh Dickins <hughd@google.com>
Date: Sat, 4 Nov 2017 18:43:06 -0700
Subject: kaiser: kaiser_flush_tlb_on_return_to_user() check PCID

From: Hugh Dickins <hughd@google.com>


Let kaiser_flush_tlb_on_return_to_user() do the X86_FEATURE_PCID
check, instead of each caller doing it inline first: nobody needs
to optimize for the noPCID case, it's clearer this way, and better
suits later changes.  Replace those no-op X86_CR3_PCID_KERN_FLUSH lines
by a BUILD_BUG_ON() in load_new_mm_cr3(), in case something changes.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/tlbflush.h |    4 ++--
 arch/x86/mm/kaiser.c            |    6 +++---
 arch/x86/mm/tlb.c               |    8 ++++----
 3 files changed, 9 insertions(+), 9 deletions(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -157,7 +157,7 @@ static inline void __native_flush_tlb(vo
 	 * back:
 	 */
 	preempt_disable();
-	if (kaiser_enabled && this_cpu_has(X86_FEATURE_PCID))
+	if (kaiser_enabled)
 		kaiser_flush_tlb_on_return_to_user();
 	native_write_cr3(native_read_cr3());
 	preempt_enable();
@@ -216,7 +216,7 @@ static inline void __native_flush_tlb_si
 	 */
 
 	if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE)) {
-		if (kaiser_enabled && this_cpu_has(X86_FEATURE_PCID))
+		if (kaiser_enabled)
 			kaiser_flush_tlb_on_return_to_user();
 		asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
 		return;
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -436,12 +436,12 @@ void kaiser_setup_pcid(void)
 
 /*
  * Make a note that this cpu will need to flush USER tlb on return to user.
- * Caller checks whether this_cpu_has(X86_FEATURE_PCID) before calling:
- * if cpu does not, then the NOFLUSH bit will never have been set.
+ * If cpu does not have PCID, then the NOFLUSH bit will never have been set.
  */
 void kaiser_flush_tlb_on_return_to_user(void)
 {
-	this_cpu_write(x86_cr3_pcid_user,
+	if (this_cpu_has(X86_FEATURE_PCID))
+		this_cpu_write(x86_cr3_pcid_user,
 			X86_CR3_PCID_USER_FLUSH | KAISER_SHADOW_PGD_OFFSET);
 }
 EXPORT_SYMBOL(kaiser_flush_tlb_on_return_to_user);
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -39,7 +39,7 @@ static void load_new_mm_cr3(pgd_t *pgdir
 {
 	unsigned long new_mm_cr3 = __pa(pgdir);
 
-	if (kaiser_enabled && this_cpu_has(X86_FEATURE_PCID)) {
+	if (kaiser_enabled) {
 		/*
 		 * We reuse the same PCID for different tasks, so we must
 		 * flush all the entries for the PCID out when we change tasks.
@@ -50,10 +50,10 @@ static void load_new_mm_cr3(pgd_t *pgdir
 		 * do it here, but can only be used if X86_FEATURE_INVPCID is
 		 * available - and many machines support pcid without invpcid.
 		 *
-		 * The line below is a no-op: X86_CR3_PCID_KERN_FLUSH is now 0;
-		 * but keep that line in there in case something changes.
+		 * If X86_CR3_PCID_KERN_FLUSH actually added something, then it
+		 * would be needed in the write_cr3() below - if PCIDs enabled.
 		 */
-		new_mm_cr3 |= X86_CR3_PCID_KERN_FLUSH;
+		BUILD_BUG_ON(X86_CR3_PCID_KERN_FLUSH);
 		kaiser_flush_tlb_on_return_to_user();
 	}
 


Patches currently in stable-queue which might be from hughd@google.com are

queue-4.4/kaiser-vmstat-show-nr_kaisertable-as-nr_overhead.patch
queue-4.4/kaiser-add-nokaiser-boot-option-using-alternative.patch
queue-4.4/kaiser-fix-unlikely-error-in-alloc_ldt_struct.patch
queue-4.4/kaiser-_pgd_alloc-without-__gfp_repeat-to-avoid-stalls.patch
queue-4.4/kaiser-kaiser_flush_tlb_on_return_to_user-check-pcid.patch
queue-4.4/x86-paravirt-dont-patch-flush_tlb_single.patch
queue-4.4/kaiser-merged-update.patch
queue-4.4/kaiser-delete-kaiser_real_switch-option.patch
queue-4.4/kaiser-kaiser_remove_mapping-move-along-the-pgd.patch
queue-4.4/kaiser-fix-perf-crashes.patch
queue-4.4/kaiser-drop-is_atomic-arg-to-kaiser_pagetable_walk.patch
queue-4.4/kaiser-load_new_mm_cr3-let-switch_user_cr3-flush-user.patch
queue-4.4/kaiser-enhanced-by-kernel-and-user-pcids.patch
queue-4.4/kaiser-x86_cr3_pcid_noflush-and-x86_cr3_pcid_user.patch
queue-4.4/kaiser-use-alternative-instead-of-x86_cr3_pcid_noflush.patch
queue-4.4/kaiser-stack-map-page_size-at-thread_size-page_size.patch
queue-4.4/kaiser-name-that-0x1000-kaiser_shadow_pgd_offset.patch
queue-4.4/kaiser-fix-regs-to-do_nmi-ifndef-config_kaiser.patch
queue-4.4/kaiser-do-not-set-_page_nx-on-pgd_none.patch
queue-4.4/kaiser-tidied-up-asm-kaiser.h-somewhat.patch
queue-4.4/kaiser-cleanups-while-trying-for-gold-link.patch
queue-4.4/kaiser-tidied-up-kaiser_add-remove_mapping-slightly.patch
queue-4.4/kaiser-fix-build-and-fixme-in-alloc_ldt_struct.patch
queue-4.4/kaiser-kernel-address-isolation.patch
queue-4.4/kaiser-enomem-if-kaiser_pagetable_walk-null.patch
queue-4.4/kaiser-asm-tlbflush.h-handle-nopge-at-lower-level.patch
queue-4.4/kaiser-paranoid_entry-pass-cr3-need-to-paranoid_exit.patch
queue-4.4/kaiser-kaiser-depends-on-smp.patch
queue-4.4/kaiser-pcid-0-for-kernel-and-128-for-user.patch