Re: [PATCH 35 of 36] x86: make pgd/pud/pmd/pte_none consistent

From: Ian Campbell
Date: Fri Feb 06 2009 - 10:30:30 EST

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
[ 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
[ 8.355161] ------------[ cut here ]------------
[ 8.355172] kernel BUG at /local/scratch/ianc/devel/kernels/paravirt/arch/x86/xen/multicalls.c:182!
[ 8.355189] invalid opcode: 0000 [#1] SMP
[ 8.355207] last sysfs file: /sys/class/net/lo/operstate
[ 8.355218] Modules linked in:
[ 8.355230]
[ 8.355239] Pid: 2213, comm: bootclean Not tainted (2.6.29-rc3-x86_32p-xenU-tip #135)
[ 8.355254] EIP: 0061:[<c010374b>] EFLAGS: 00010002 CPU: 1
[ 8.355267] EIP is at xen_mc_flush+0x19b/0x1b0
[ 8.355278] EAX: 00000000 EBX: 00000000 ECX: c10cc060 EDX: 00000000
[ 8.355290] ESI: 00000000 EDI: 00000001 EBP: c4c61e70 ESP: c4c61e40
[ 8.355302] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0069
[ 8.355314] Process bootclean (pid: 2213, ti=c4c60000 task=c5ad3460 task.ti=c4c60000)
[ 8.355328] Stack:
[ 8.355336] c0367d84 00000001 00000001 aaaaaaaa aaaaaaaa ffffffda c01059f1 c10cc060
[ 8.355372] c10c0060 c4c7a6d4 bfabf790 bfabf790 c4c61e80 c0105a60 c4c7a6d4 c4c7a580
[ 8.355413] c4c61ea0 c0126643 00000000 80000000 00000025 08428067 80000000 c4c

Didn't figure out why yet.

>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
>
> ---
> arch/x86/include/asm/pgtable.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -503,7 +503,7 @@
> {
> /* Only check low word on 32-bit platforms, since it might be
> out of sync with upper half. */
> - return !(unsigned long)native_pmd_val(pmd);
> + return (unsigned long)native_pmd_val(pmd) == 0;
> }
>
> static inline unsigned long pmd_page_vaddr(pmd_t pmd)
> @@ -568,7 +568,7 @@
> #if PAGETABLE_LEVELS > 2
> static inline int pud_none(pud_t pud)
> {
> - return pud_val(pud) == 0;
> + return native_pud_val(pud) == 0;
> }
>
> static inline int pud_present(pud_t pud)
> @@ -643,7 +643,7 @@
>
> static inline int pgd_none(pgd_t pgd)
> {
> - return !pgd_val(pgd);
> + return !native_pgd_val(pgd);
> }
> #endif /* PAGETABLE_LEVELS > 3 */
>
>
>
> --
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--
Ian Campbell

I can resist anything but temptation.

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