On 07/18/17 at 02:08pm, Dou Liyang wrote:
> Hi, Zheng
>
> At 07/18/2017 01:18 PM, Zheng, Lv wrote:
> > Hi,
> >
> > Can the problem be fixed by invoking acpi_put_table() for mapped DMAR table?
>
> Invoking acpi_put_table() is my first choice. But it made the kernel
> *panic* when we try to get the table again in intel_iommu_init() in
> late stage.
>
> I am also confused that:
>
> There are two places where we used DMAR table in Linux:
>
> 1) In detect_intel_iommu() in ACPI early stage:
>
> ...
> status = acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_tbl);
> ....
> if (dmar_tbl) {
> acpi_put_table(dmar_tbl);
> dmar_tbl = NULL;
> }
>
> 2) In dmar_table_init() in ACPI late stage:
>
> ...
> status = acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_tbl);
> ...
>
> As we know, dmar_table_init() is called by intel_iommu_init() and
> intel_prepare_irq_remapping().
>
> When I invoked acpi_put_table() in the intel_prepare_irq_remapping() in
> early stage like 1) shows, kernel will panic.
That's because acpi_put_table() will make the table pointer be NULL,
while dmar_table_init() will skip parse_dmar_table() calling if
dmar_table_initialized is set to 1 in intel_prepare_irq_remapping().
Dmar hardware support interrupt remapping and io remapping separately. But
intel_iommu_init() is called later than intel_prepare_irq_remapping().
So what if make dmar_table_init() a reentrant function? You can just
have a try, but maybe not a good idea, the dmar table will be parsed
twice.
>
>
> Thanks,
>
> dou.
> >
> > Thanks
> > Lv
> >
> > > From: Dou Liyang [mailto:douly.f...@cn.fujitsu.com]
> > > Sent: Friday, July 14, 2017 1:53 PM
> > > To: x...@kernel.org; linux-kernel@vger.kernel.org
> > > Cc: t...@linutronix.de; mi...@kernel.org; h...@zytor.com;
> > > ebied...@xmission.com; b...@redhat.com;
> > > pet...@infradead.org; izumi.t...@jp.fujitsu.com;
> > > tokunaga.kei...@jp.fujitsu.com; Dou Liyang
> > > <douly.f...@cn.fujitsu.com>; linux-a...@vger.kernel.org; Rafael J.
> > > Wysocki <r...@rjwysocki.net>; Zheng,
> > > Lv <lv.zh...@intel.com>; Julian Wollrath <jwollr...@web.de>
> > > Subject: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization
> > > earlier
> > >
> > > Linux uses acpi_early_init() to put the ACPI table management into
> > > the late stage from the early stage where the mapped ACPI tables is
> > > temporary and should be unmapped.
> > >
> > > But, now initializing interrupt delivery mode should map and parse the
> > > DMAR table earlier in the early stage. This causes an ACPI error when
> > > Linux reallocates the ACPI root tables. Because Linux doesn't unmapped
> > > the DMAR table after using in the early stage.
> > >
> > > Invoke acpi_early_init() earlier before late_time_init(), Keep the DMAR
> > > be mapped and parsed in late stage like before.
> > >
> > > Reported-by: Xiaolong Ye <xiaolong...@intel.com>
> > > Signed-off-by: Dou Liyang <douly.f...@cn.fujitsu.com>
> > > Cc: linux-a...@vger.kernel.org
> > > Cc: Rafael J. Wysocki <r...@rjwysocki.net>
> > > Cc: Zheng, Lv <lv.zh...@intel.com>
> > > Cc: Julian Wollrath <jwollr...@web.de>
> > > ---
> > > Test in my own PC(Lenovo M4340).
> > > Ask help for doing regression testing for the bug said in commit
> > > c4e1acbb35e4
> > > ("ACPI / init: Invoke early ACPI initialization later").
> > >
> > > init/main.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/init/main.c b/init/main.c
> > > index df58a41..7a09467 100644
> > > --- a/init/main.c
> > > +++ b/init/main.c
> > > @@ -654,12 +654,12 @@ asmlinkage __visible void __init start_kernel(void)
> > > kmemleak_init();
> > > setup_per_cpu_pageset();
> > > numa_policy_init();
> > > + acpi_early_init();
> > > if (late_time_init)
> > > late_time_init();
> > > calibrate_delay();
> > > pidmap_init();
> > > anon_vma_init();
> > > - acpi_early_init();
> > > #ifdef CONFIG_X86
> > > if (efi_enabled(EFI_RUNTIME_SERVICES))
> > > efi_enter_virtual_mode();
> > > --
> > > 2.5.5
> > >
> > >
> >
> >
> >
> >
>
>
