Re: [Xen-devel] [PATCH V2 2/6] iommu/arm: Add ability to handle deferred probing request

[Oleksandr <olekstysh@xxxxxxxxx>]

Hi, Julien


> > I noticed there was already a panic() in iommu_setup() just in case 
> > the user
> > force the use of IOMMU but they were not initialized. I was 
> > half-tempted to set
> > iommu_force to true for Arm, but I think this is a different issue.
> >
> > So here my take (not tested nor compiled).
> Thank you. I will check it and come back with results.
I have preliminary tested it with my IPMMU series including new 
modification of "deferred probing" patch (attached). Being honest my 
series is not based on the *current* staging, but not too outdated.
So, your patch works as expected in the following scenarios:

1. [No panic] Without IOMMU driver in Xen (#CONFIG_IPMMU_VMSA is not set).

2. [No panic] IOMMU driver is present, but reports it is cannot be used 
in Xen (P2M sharing not supported, etc) by returning -ENODEV.
3. [No panic] IOMMU is globally disabled in command line "iommu=0".

4. [No panic] IOMMU driver requests deferred probing until the last 
device in DT is initialized, after that all deferred devices get 
initialized.
5. [Panic] IOMMU driver returns an error (other than -EBADF and -ENODEV) 
at the very beginning/when a part of devices are already initialized.
6. [Panic] IOMMU driver always returns deferred probing/returns an error 
other than -EAGAIN after deferred probing.

> > diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> > index 2c5d1372c0..8f94f618b0 100644
> > --- a/xen/arch/arm/setup.c
> > +++ b/xen/arch/arm/setup.c
> > @@ -755,6 +755,7 @@ void __init start_xen(unsigned long 
> > boot_phys_offset,
> >           .max_grant_frames = gnttab_dom0_frames(),
> >           .max_maptrack_frames = opt_max_maptrack_frames,
> >       };
> > +    int rc;
> >         dcache_line_bytes = read_dcache_line_bytes();
> >   @@ -890,7 +891,9 @@ void __init start_xen(unsigned long 
> > boot_phys_offset,
> >         setup_virt_paging();
> >   -    iommu_setup();
> > +    rc = iommu_setup();
> > +    if ( !iommu_enabled && rc != -ENODEV )
> > +        panic("Couldn't configure correctly all the IOMMUs.");
"\n" should be added.



--
Regards,

Oleksandr Tyshchenko

Attachment: 0001-iommu-arm-Add-ability-to-handle-deferred-probing-req.patch
Description: Text Data

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