> -----Original Message----- > From: Mark Rutland [mailto:mark.rutland@xxxxxxx] > Sent: Tuesday, February 09, 2016 10:08 AM > To: Stuart Yoder <stuart.yoder@xxxxxxx> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx>; Robin Murphy <robin.murphy@xxxxxxx>; > robh+dt@xxxxxxxxxx; frowand.list@xxxxxxxxx; grant.likely@xxxxxxxxxx; > devicetree@xxxxxxxxxxxxxxx; david.daney@xxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] of/irq: Fix msi-map calculation for nonzero rid-base > > On Tue, Feb 09, 2016 at 03:56:55PM +0000, Stuart Yoder wrote: > > > > > -----Original Message----- > > > From: Marc Zyngier [mailto:marc.zyngier@xxxxxxx] > > > Sent: Tuesday, February 09, 2016 6:06 AM > > > To: Robin Murphy <robin.murphy@xxxxxxx>; robh+dt@xxxxxxxxxx; frowand.list@xxxxxxxxx; > > > grant.likely@xxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx > > > Cc: mark.rutland@xxxxxxx; david.daney@xxxxxxxxxx; Stuart Yoder > <stuart.yoder@xxxxxxx>; > > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > stable@xxxxxxxxxxxxxxx > > > Subject: Re: [PATCH] of/irq: Fix msi-map calculation for nonzero rid-base > > > > > > Hi Robin, > > > > > > On 09/02/16 11:04, Robin Murphy wrote: > > > > The existing msi-map code is fine for shifting the entire RID space > > > > upwards, but attempting finer-grained remapping reveals a bug. It turns > > > > out that we are mistakenly treating the msi-base part as an offset, not > > > > as a new base to remap onto, so things get squiffy when rid-base is > > > > nonzero. Fix this, and at the same time add a sanity check against > > > > having msi-map-mask clash with a nonzero rid-base, as that's another > > > > thing one can easily get wrong. > > > > > > > > CC: <stable@xxxxxxxxxxxxxxx> > > > > Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx> > > > > > > Looks like Stuart and you both found the same bug at the same time: > > > https://lkml.org/lkml/2016/2/8/1066 > > > > > > but yours seem more correct to me (the rid_base masking in Stuart's > > > version seems odd). > > > > > > > --- > > > > drivers/of/irq.c | 9 ++++++++- > > > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/of/irq.c b/drivers/of/irq.c > > > > index 7ee21ae..e7bfc17 100644 > > > > --- a/drivers/of/irq.c > > > > +++ b/drivers/of/irq.c > > > > @@ -635,6 +635,13 @@ static u32 __of_msi_map_rid(struct device *dev, struct > > > device_node **np, > > > > msi_base = be32_to_cpup(msi_map + 2); > > > > rid_len = be32_to_cpup(msi_map + 3); > > > > > > > > + if (rid_base & ~map_mask) { > > > > + dev_err(parent_dev, > > > > + "Invalid msi-map translation - msi-map-mask (0x%x) ignores > rid- > > > base (0x%x)\n", > > > > + map_mask, rid_base); > > > > + return rid_out; > > > > + } > > > > + > > > > msi_controller_node = of_find_node_by_phandle(phandle); > > > > > > > > matched = (masked_rid >= rid_base && > > > > @@ -654,7 +661,7 @@ static u32 __of_msi_map_rid(struct device *dev, struct > device_node > > > **np, > > > > if (!matched) > > > > return rid_out; > > > > > > > > - rid_out = masked_rid + msi_base; > > > > + rid_out = masked_rid - rid_base + msi_base; > > > > dev_dbg(dev, > > > > "msi-map at: %s, using mask %08x, rid-base: %08x, msi-base: %08x, > length: > > > %08x, rid: %08x -> %08x\n", > > > > dev_name(parent_dev), map_mask, rid_base, msi_base, > > > > > > > > This computation: masked_rid - rid_base > > > > ...doesn't seem right to me. We are taking a rid that > > has been already masked and subtracting a rid base that has > > not been masked. > > The binding only mentions that the input RID is masked, not the base, so > that seems correct to me. > > > I don't see how you can combine masked and unmasked values in the same > > calculation. > > > > Say I have this msi mapping: > > > > msi-map = <0x0100 &its 0x11 0x1>; > > msi-map-mask = <0xff>; > > > > I'd say that this is an inconsistent set of properties, and it's > probably worth warning if we encounter this. There is no possible way > that rid-base can be encountered. > > > masked_rid = 0x0 > > rid_base = 0x0100 > > msi_base = 0x11 > > > > masked_rid - rid_base is 0x0 - 0x0100...which does not > > give the msi index/offset we want. > > > > Correct final answer should be 0x11. > > You can unambiguously describe this with: > > msi-map = <0x00 &its 0x11 0x1>; > msi-map-mask = <0xff>; > > This is exactly the pattern we follow in example 2 in the binding > document. > > > In my patch I masked the rid_base so it can be subtracted > > from the masked_rid. > > > > masked_rid_base = 0x00 > > > > msi_base + (masked_rid - masked_rid_base) = 0x11 > > As above, I think that this is an inconsistent DT, and we should > warn/fail in that case. Thanks...understand now. I'll test Robin's patch and confirm that it works as is for me. Thanks, Stuart -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
