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

x86/mm: Make flush_tlb_mm_range() more predictable

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-mm-make-flush_tlb_mm_range-more-predictable.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 ce27374fabf553153c3f53efcaa9bfab9216bd8c Mon Sep 17 00:00:00 2001

From: Andy Lutomirski luto@kernel.org Date: Sat, 22 Apr 2017 00:01:21 -0700 Subject: x86/mm: Make flush_tlb_mm_range() more predictable

From: Andy Lutomirski luto@kernel.org

commit ce27374fabf553153c3f53efcaa9bfab9216bd8c upstream.

I'm about to rewrite the function almost completely, but first I want to get a functional change out of the way. Currently, if flush_tlb_mm_range() does not flush the local TLB at all, it will never do individual page flushes on remote CPUs. This seems to be an accident, and preserving it will be awkward. Let's change it first so that any regressions in the rewrite will be easier to bisect and so that the rewrite can attempt to change no visible behavior at all.

The fix is simple: we can simply avoid short-circuiting the calculation of base_pages_to_flush.

As a side effect, this also eliminates a potential corner case: if tlb_single_page_flush_ceiling == TLB_FLUSH_ALL, flush_tlb_mm_range() could have ended up flushing the entire address space one page at a time.

Signed-off-by: Andy Lutomirski luto@kernel.org Acked-by: Dave Hansen dave.hansen@intel.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Borislav Petkov bp@alien8.de Cc: Brian Gerst brgerst@gmail.com Cc: Denys Vlasenko dvlasenk@redhat.com Cc: H. Peter Anvin hpa@zytor.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Michal Hocko mhocko@suse.com Cc: Nadav Amit namit@vmware.com Cc: Peter Zijlstra peterz@infradead.org Cc: Rik van Riel riel@redhat.com Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/4b29b771d9975aad7154c314534fec235618175a.1492844372... Signed-off-by: Ingo Molnar mingo@kernel.org Cc: Hugh Dickins hughd@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/mm/tlb.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -292,6 +292,12 @@ void flush_tlb_mm_range(struct mm_struct unsigned long base_pages_to_flush = TLB_FLUSH_ALL;

preempt_disable(); + + if ((end != TLB_FLUSH_ALL) && !(vmflag & VM_HUGETLB)) + base_pages_to_flush = (end - start) >> PAGE_SHIFT; + if (base_pages_to_flush > tlb_single_page_flush_ceiling) + base_pages_to_flush = TLB_FLUSH_ALL; + if (current->active_mm != mm) { /* Synchronize with switch_mm. */ smp_mb(); @@ -308,15 +314,11 @@ void flush_tlb_mm_range(struct mm_struct goto out; }

- if ((end != TLB_FLUSH_ALL) && !(vmflag & VM_HUGETLB)) - base_pages_to_flush = (end - start) >> PAGE_SHIFT; - /* * Both branches below are implicit full barriers (MOV to CR or * INVLPG) that synchronize with switch_mm. */ - if (base_pages_to_flush > tlb_single_page_flush_ceiling) { - base_pages_to_flush = TLB_FLUSH_ALL; + if (base_pages_to_flush == TLB_FLUSH_ALL) { count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL); local_flush_tlb(); } else {

Patches currently in stable-queue which might be from luto@kernel.org are

queue-4.4/x86-vm86-32-switch-to-flush_tlb_mm_range-in-mark_screen_rdonly.patch queue-4.4/x86-mm-make-flush_tlb_mm_range-more-predictable.patch queue-4.4/x86-mm-remove-flush_tlb-and-flush_tlb_current_task.patch