On 9/11/21 4:35 PM, Sasha Levin wrote:

On Fri, Sep 10, 2021 at 07:48:18AM +0200, Cédric Le Goater wrote:

quoted

On 9/10/21 2:14 AM, Sasha Levin wrote:

quoted

From: Cédric Le Goater <clg@kaod.org>

[ Upstream commit 1753081f2d445f9157550692fcc4221cd3ff0958 ]

PCI MSIs now live in an MSI domain but the underlying calls, which
will EOI the interrupt in real mode, need an HW IRQ number mapped in
the XICS IRQ domain. Grab it there.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210701132750.1475580-31-clg@kaod.org (local)
Signed-off-by: Sasha Levin <sashal@kernel.org>

Why are we backporting this patch in stable trees ?

It should be fine but to compile, we need a partial backport of commit
51be9e51a800 ("KVM: PPC: Book3S HV: XIVE: Fix mapping of passthrough
interrupts") which exports irq_get_default_host().

Or, I can drop it if it makes no sense?

Yes I would. 

It makes sense only with the full patchset, the one reworking PCI MSI 
support in the PPC pSeries and PowerNV platforms.

Thanks,

C.