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SubjectRe: [PATCH v2] powerpc/pci: unmap legacy INTx interrupts when a PHB is removed
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Qian Cai <cai@redhat.com> writes:
> On Wed, 2020-09-23 at 09:06 +0200, Cédric Le Goater wrote:
>> On 9/23/20 2:33 AM, Qian Cai wrote:
>> > On Fri, 2020-08-07 at 12:18 +0200, Cédric Le Goater wrote:
>> > > When a passthrough IO adapter is removed from a pseries machine using
>> > > hash MMU and the XIVE interrupt mode, the POWER hypervisor expects the
>> > > guest OS to clear all page table entries related to the adapter. If
>> > > some are still present, the RTAS call which isolates the PCI slot
>> > > returns error 9001 "valid outstanding translations" and the removal of
>> > > the IO adapter fails. This is because when the PHBs are scanned, Linux
>> > > maps automatically the INTx interrupts in the Linux interrupt number
>> > > space but these are never removed.
>> > >
>> > > To solve this problem, we introduce a PPC platform specific
>> > > pcibios_remove_bus() routine which clears all interrupt mappings when
>> > > the bus is removed. This also clears the associated page table entries
>> > > of the ESB pages when using XIVE.
>> > >
>> > > For this purpose, we record the logical interrupt numbers of the
>> > > mapped interrupt under the PHB structure and let pcibios_remove_bus()
>> > > do the clean up.
>> > >
>> > > Since some PCI adapters, like GPUs, use the "interrupt-map" property
>> > > to describe interrupt mappings other than the legacy INTx interrupts,
>> > > we can not restrict the size of the mapping array to PCI_NUM_INTX. The
>> > > number of interrupt mappings is computed from the "interrupt-map"
>> > > property and the mapping array is allocated accordingly.
>> > >
>> > > Cc: "Oliver O'Halloran" <oohall@gmail.com>
>> > > Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
>> > > Signed-off-by: Cédric Le Goater <clg@kaod.org>
>> >
>> > Some syscall fuzzing will trigger this on POWER9 NV where the traces pointed
>> > to
>> > this patch.
>> >
>> > .config: https://gitlab.com/cailca/linux-mm/-/blob/master/powerpc.config
>>
>> OK. The patch is missing a NULL assignement after kfree() and that
>> might be the issue.
>>
>> I did try PHB removal under PowerNV, so I would like to understand
>> how we managed to remove twice the PCI bus and possibly reproduce.
>> Any chance we could grab what the syscall fuzzer (syzkaller) did ?
>
> Any update on this? Maybe Michael or Stephen could drop this for now, so our
> fuzzing could continue to find something else new?

Someone send me a revert?

cheers

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