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SubjectRe: [PATCH 35 of 36] x86: make pgd/pud/pmd/pte_none consistent
On Fri, 2009-02-06 at 15:45 +0000, Ian Campbell wrote:
> On Fri, 2009-02-06 at 15:29 +0000, Ian Campbell wrote:
> > On Thu, 2009-02-05 at 11:31 -0800, Jeremy Fitzhardinge wrote:
> > > The _none test is done differently for every level of the pagetable.
> > > Standardize them by:
> > >
> > > 1: Use the native_X_val to extract the raw entry, with no need to go
> > > via paravirt_ops, diff -r 1d0646d0d319 arch/x86/include/asm/pgtable.h, and
> > > 2: Compare with 0 rather than using a boolean !, since they are actually values
> > > and not booleans.
> >
> > In a 32 bit Xen guest this one causes
> >
> > [ 8.354898] 1 multicall(s) failed: cpu 1
>
> Spoke too soon, it's not as 100% reliably reproducing as I thought which
> confused my bisection attempt. Will try and locate the real culprit...

Real culprit was somewhere else entirely:

Subject: Fix xen_flush_tlb_others after const cpumask changes

The commit
commit 4595f9620cda8a1e973588e743cf5f8436dd20c6
Author: Rusty Russell <rusty@rustcorp.com.au>
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@citrix.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mike Travis <travis@sgi.com>
Cc: x86@kernel.org
---
arch/x86/xen/mmu.c | 3 ---
1 files changed, 0 insertions(+), 3 deletions(-)

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);
}

--
1.5.6.5

--
Ian Campbell

We are now enjoying total mutual interaction in an imaginary hot tub ...



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