Re: [PATCH] iommu/amd: Fix iommu remap panic while amd_iommu is set to disable

[Huang Rui <ray.huang@amd.com>]

On Tue, Mar 16, 2021 at 09:16:34PM +0800, Joerg Roedel wrote:
> Hi Huang,
> 
> On Thu, Mar 11, 2021 at 10:28:07PM +0800, Huang Rui wrote:
> > diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> > index f0adbc48fd17..a08e885403b7 100644
> > --- a/drivers/iommu/amd/iommu.c
> > +++ b/drivers/iommu/amd/iommu.c
> > @@ -3862,7 +3862,7 @@ static int irq_remapping_select(struct irq_domain *d, struct irq_fwspec *fwspec,
> >  	else if (x86_fwspec_is_hpet(fwspec))
> >  		devid = get_hpet_devid(fwspec->param[0]);
> >  
> > -	if (devid < 0)
> > +	if (devid < 0 || !amd_iommu_rlookup_table)
> >  		return 0;
> 
> The problem is deeper than this fix suggests. I prepared other fixes for
> this particular problem. Please find them here:
> 

Thanks for the comments. Could you please elaborate this?

Do you mean while amd_iommu=off, we won't prepare the IVRS, and even
needn't get all ACPI talbes. Because they are never be used and the next
state will always goes into IOMMU_CMDLINE_DISABLED, am I right?

Thanks,
Ray

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> 
> Regards,
> 
> 	Joerg