On 19 March 2018 at 15:37, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, Mar 19, 2018 at 08:37:07AM +0100, Greg KH wrote: >> On Mon, Mar 19, 2018 at 03:28:40PM +0800, Ard Biesheuvel wrote: >> > On 19 March 2018 at 15:27, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: >> > > Commit 4f2c7583e33e upstream. >> > > >> > > When struct its_device instances are created, the nr_ites member >> > > will be set to a power of 2 that equals or exceeds the requested >> > > number of MSIs passed to the msi_prepare() callback. At the same >> > > time, the LPI map is allocated to be some multiple of 32 in size, >> > > where the allocated size may be less than the requested size >> > > depending on whether a contiguous range of sufficient size is >> > > available in the global LPI bitmap. >> > > >> > > This may result in the situation where the nr_ites < nr_lpis, and >> > > since nr_ites is what we program into the hardware when we map the >> > > device, the additional LPIs will be non-functional. >> > > >> > > For bog standard hardware, this does not really matter. However, >> > > in cases where ITS device IDs are shared between different PCIe >> > > devices, we may end up allocating these additional LPIs without >> > > taking into account that they don't actually work. >> > > >> > > So let's make nr_ites at least 32. This ensures that all allocated >> > > LPIs are 'live', and that its_alloc_device_irq() will fail when >> > > attempts are made to allocate MSIs beyond what was allocated in >> > > the first place. >> > > >> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> >> > > [maz: updated comment] >> > > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> >> > > [ardb: trivial tweak of unrelated context] >> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> >> > > --- >> > >> > Please apply to v4.9 >> >> What about 4.14.y and 4.15.y? Why only add it to one really old tree, >> you don't want people updating to a newer kernel and have a regression, >> right? > > Ah, now I see your other email, sorry, nevermind... No worries. Actually, this version applies cleanly to v4.4 as well, so could you please add it there as well?