linux-kernel - [PATCH v2 3/3] x86/mm: Fix flush_tlb

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Date:   Fri, 21 Apr 2017 11:15:13 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Nadav Amit <namit@...are.com>, Michal Hocko <mhocko@...e.com>,
        Sasha Levin <sasha.levin@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH v2 3/3] x86/mm: Fix flush_tlb_page() on Xen

flush_tlb_page() passes a bogus range to flush_tlb_others() and
expects the latter to fix it up.  native_flush_tlb_others() has the
fixup but Xen's version doesn't.  Move the fixup to
flush_tlb_others().

AFAICS the only real effect is that, without this fix, Xen would
flush everything instead of just the one page on remote vCPUs in
when flush_tlb_page() was called.

Cc: Rik van Riel <riel@...hat.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Nadav Amit <namit@...are.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Sasha Levin <sasha.levin@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Fixes: e7b52ffd45a6 ("x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range")
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/mm/tlb.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 9db9260a5e9f..6e7bedf69af7 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -263,8 +263,6 @@ void native_flush_tlb_others(const struct cpumask *cpumask,
 {
 	struct flush_tlb_info info;
 
-	if (end == 0)
-		end = start + PAGE_SIZE;
 	info.flush_mm = mm;
 	info.flush_start = start;
 	info.flush_end = end;
@@ -378,7 +376,7 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long start)
 	}
 
 	if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
-		flush_tlb_others(mm_cpumask(mm), mm, start, 0UL);
+		flush_tlb_others(mm_cpumask(mm), mm, start, start + PAGE_SIZE);
 
 	preempt_enable();
 }
-- 
2.9.3