Re: [PATCH 08/10] iommu/amd: drop the lock while allocating new irq remap table

[Joerg Roedel]

On Fri, Feb 23, 2018 at 11:27:34PM +0100, Sebastian Andrzej Siewior wrote:
> The irq_remap_table is allocated while the iommu_table_lock is held with
> interrupts disabled. While this works it makes RT scream very loudly.
> >From looking at the call sites, all callers are in the early device
> initialisation (apic_bsp_setup(), pci_enable_device(),
> pci_enable_msi()) so make sense to drop the lock which also enables
> interrupts and try to allocate that memory with GFP_KERNEL instead
> GFP_ATOMIC.
> 
> Since during the allocation the iommu_table_lock is dropped, we need to
> recheck if table exists after the lock has been reacquired. I *think*
> that it is impossible that the "devid" entry appears in irq_lookup_table
> while the lock is dropped since the same device can only be probed once.
> It is more likely that another device added an `alias' entry. However I
> check for both cases, just to be sure.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

This looks like it conflicts with the x86/amd branch as well.