[Xen-devel] [PATCH] xen: Fix xen_flush_tlb_others

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>

   xen: Fix xen_flush_tlb_others
   
   The commit
       commit 4595f9620cda8a1e973588e743cf5f8436dd20c6
       Author: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
       Date:   Sat Jan 10 21:58:09 2009 -0800
   
           x86: change flush_tlb_others to take a const struct cpumask
   
   causes xen_flush_tlb_others to allocate a multicall and then issue it
   without initializing it in the case where the cpumask is empty,
   leading to:
   
           [    8.354898] 1 multicall(s) failed: cpu 1
           [    8.354921] Pid: 2213, comm: bootclean Not tainted 
2.6.29-rc3-x86_32p-xenU-tip #135
           [    8.354937] Call Trace:
           [    8.354955]  [<c01036e3>] xen_mc_flush+0x133/0x1b0
           [    8.354971]  [<c0105d2a>] ? xen_force_evtchn_callback+0x1a/0x30
           [    8.354988]  [<c0105a60>] xen_flush_tlb_others+0xb0/0xd0
           [    8.355003]  [<c0126643>] flush_tlb_page+0x53/0xa0
           [    8.355018]  [<c0176a80>] do_wp_page+0x2a0/0x7c0
           [    8.355034]  [<c0238f0a>] ? notify_remote_via_irq+0x3a/0x70
           [    8.355049]  [<c0178950>] handle_mm_fault+0x7b0/0xa50
           [    8.355065]  [<c0131a3e>] ? wake_up_new_task+0x8e/0xb0
           [    8.355079]  [<c01337b5>] ? do_fork+0xe5/0x320
           [    8.355095]  [<c0121919>] do_page_fault+0xe9/0x240
           [    8.355109]  [<c0121830>] ? do_page_fault+0x0/0x240
           [    8.355125]  [<c032457a>] error_code+0x72/0x78
           [    8.355139]   call  1/1: op=2863311530 arg=[aaaaaaaa] result=-38  
   xen_flush_tlb_others+0x41/0xd0
   
   Since empty cpumasks are rare and undoing an xen_mc_entry() is tricky
   just issue such requests normally.
   
   Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
   Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
   Cc: Ingo Molnar <mingo@xxxxxxx>
   Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
   Cc: Mike Travis <travis@xxxxxxx>
   Cc: x86@xxxxxxxxxx

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index d2e8ed1..319bd40 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1273,8 +1273,6 @@ static void xen_flush_tlb_others(const struct cpumask 
*cpus,
        /* Remove us, and any offline CPUS. */
        cpumask_and(to_cpumask(args->mask), cpus, cpu_online_mask);
        cpumask_clear_cpu(smp_processor_id(), to_cpumask(args->mask));
-       if (unlikely(cpumask_empty(to_cpumask(args->mask))))
-               goto issue;

        if (va == TLB_FLUSH_ALL) {
                args->op.cmd = MMUEXT_TLB_FLUSH_MULTI;
@@ -1285,7 +1283,6 @@ static void xen_flush_tlb_others(const struct cpumask 
*cpus,

        MULTI_mmuext_op(mcs.mc, &args->op, 1, NULL, DOMID_SELF);

-issue:
        xen_mc_issue(PARAVIRT_LAZY_MMU);
}




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