RE: 174cc7187e6f ACPICA: Tables: Back port acpi_get_table_with_size() and early_acpi_os_unmap_memory() from Linux kernel

[Zheng, Lv]

Hi,

> From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi-owner@xxxxxxxxxxxxxxx] On Behalf Of Borislav
> Petkov
> Subject: Re: 174cc7187e6f ACPICA: Tables: Back port acpi_get_table_with_size() and
> early_acpi_os_unmap_memory() from Linux kernel
> 
> On Sun, Jan 08, 2017 at 03:20:20AM +0100, Rafael J. Wysocki wrote:
> >  drivers/iommu/amd_iommu_init.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Index: linux-pm/drivers/iommu/amd_iommu_init.c
> > ===================================================================
> > --- linux-pm.orig/drivers/iommu/amd_iommu_init.c
> > +++ linux-pm/drivers/iommu/amd_iommu_init.c
> > @@ -2230,7 +2230,7 @@ static int __init early_amd_iommu_init(v
> >  	 */
> >  	ret = check_ivrs_checksum(ivrs_base);
> >  	if (ret)
> > -		return ret;
> > +		goto out;
> >
> >  	amd_iommu_target_ivhd_type = get_highest_supported_ivhd_type(ivrs_base);
> >  	DUMP_printk("Using IVHD type %#x\n", amd_iommu_target_ivhd_type);
> 
> Good catch, this one needs to be applied regardless.
> 
> However, it doesn't fix my issue though.
> 
> But I think I have it - I went and applied the well-proven debugging
> technique of sprinkling printks around. Here's what I'm seeing:
> 
> early_amd_iommu_init()
> |-> acpi_put_table(ivrs_base);
> |-> acpi_tb_put_table(table_desc);
> |-> acpi_tb_invalidate_table(table_desc);
> |-> acpi_tb_release_table(...)
> |-> acpi_os_unmap_memory
> |-> acpi_os_unmap_iomem
> |-> acpi_os_map_cleanup
> |-> synchronize_rcu_expedited	<-- the kernel/rcu/tree_exp.h version with CONFIG_PREEMPT_RCU=y
> 
> Now that function goes and sends IPIs, i.e., schedule_work()
> but this is too early - we haven't even done workqueue_init().
> Actually, from looking at the callstack, we do
> kernel_init_freeable->native_smp_prepare_cpus() and workqueue_init()
> comes next.
> 
> And this makes sense because the splat rIP points to __queue_work() but
> we haven't done that yet.
> 
> So that acpi_put_table() is happening too early. Looks like AMD IOMMU
> should not put the table but WTH do I know?!
> 
> In any case, commenting out:
> 
>         acpi_put_table(ivrs_base);
>         ivrs_base = NULL;
> 
> and the end of early_amd_iommu_init() makes the box boot again.

So please help to comment out these 2 lines (with descriptions and do not delete them).
Until acpi_os_unmap_memory() is able to handle such an early case.

Thanks and best regards
Lv

> 
> --
> Regards/Gruss,
>     Boris.
> 
> Good mailing practices for 400: avoid top-posting and trim the reply.
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