Re: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization earlier

[Dou Liyang]

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.


Thanks,

	dou.
> Thanks
> Lv
>
> > From: Dou Liyang [mailto:douly.fnst@xxxxxxxxxxxxxx]
> > Sent: Friday, July 14, 2017 1:53 PM
> > To: x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Cc: tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; hpa@xxxxxxxxx; ebiederm@xxxxxxxxxxxx; bhe@xxxxxxxxxx;
> > peterz@xxxxxxxxxxxxx; izumi.taku@xxxxxxxxxxxxxx; tokunaga.keiich@xxxxxxxxxxxxxx; Dou Liyang
> > <douly.fnst@xxxxxxxxxxxxxx>; linux-acpi@xxxxxxxxxxxxxxx; Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>; Zheng,
> > Lv <lv.zheng@xxxxxxxxx>; Julian Wollrath <jwollrath@xxxxxx>
> > 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.ye@xxxxxxxxx>
> > Signed-off-by: Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>
> > Cc: linux-acpi@xxxxxxxxxxxxxxx
> > Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> > Cc: Zheng, Lv <lv.zheng@xxxxxxxxx>
> > Cc: Julian Wollrath <jwollrath@xxxxxx>
> > ---
> > 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