Messages in this thread | | | Subject | Re: [PATCH v2] ACPI/IORT: Do not blindly trust DMA masks from firmware | From | Robin Murphy <> | Date | Fri, 22 Jan 2021 19:17:59 +0000 |
| |
On 2021-01-22 17:50, Moritz Fischer wrote: > Hi Robin, > > On Fri, Jan 22, 2021 at 02:42:05PM +0000, Robin Murphy wrote: >> On 2021-01-22 01:24, Moritz Fischer wrote: >>> Address issue observed on real world system with suboptimal IORT table >>> where DMA masks of PCI devices would get set to 0 as result. >>> >>> iort_dma_setup() would query the root complex'/named component IORT >>> entry for a DMA mask, and use that over the one the device has been >>> configured with earlier. >>> >>> Ideally we want to use the minimum mask of what the IORT contains for >>> the root complex and what the device was configured with. >>> >>> Fixes: 5ac65e8c8941 ("ACPI/IORT: Support address size limit for root complexes") >>> Signed-off-by: Moritz Fischer <mdf@kernel.org> >>> --- >>> >>> Changes from v1: >>> - Changed warning to FW_BUG >>> - Warn for both Named Component or Root Complex >>> - Replaced min_not_zero() with min() >>> >>> --- >>> drivers/acpi/arm64/iort.c | 14 ++++++++++++-- >>> 1 file changed, 12 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c >>> index d4eac6d7e9fb..2494138a6905 100644 >>> --- a/drivers/acpi/arm64/iort.c >>> +++ b/drivers/acpi/arm64/iort.c >>> @@ -1107,6 +1107,11 @@ static int nc_dma_get_range(struct device *dev, u64 *size) >>> ncomp = (struct acpi_iort_named_component *)node->node_data; >>> + if (!ncomp->memory_address_limit) { >>> + pr_warn(FW_BUG "Named component missing memory address limit\n"); >>> + return -EINVAL; >>> + } >>> + >>> *size = ncomp->memory_address_limit >= 64 ? U64_MAX : >>> 1ULL<<ncomp->memory_address_limit; >>> @@ -1126,6 +1131,11 @@ static int rc_dma_get_range(struct device *dev, u64 *size) >>> rc = (struct acpi_iort_root_complex *)node->node_data; >>> + if (!rc->memory_address_limit) { >>> + pr_warn(FW_BUG "Root complex missing memory address limit\n"); >>> + return -EINVAL; >>> + } >>> + >>> *size = rc->memory_address_limit >= 64 ? U64_MAX : >>> 1ULL<<rc->memory_address_limit; >>> @@ -1173,8 +1183,8 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size) >>> end = dmaaddr + size - 1; >>> mask = DMA_BIT_MASK(ilog2(end) + 1); >>> dev->bus_dma_limit = end; >>> - dev->coherent_dma_mask = mask; >>> - *dev->dma_mask = mask; >>> + dev->coherent_dma_mask = min(dev->coherent_dma_mask, mask); >>> + *dev->dma_mask = min(*dev->dma_mask, mask); >> >> Oops, I got so distracted by the "not_zero" aspect in v1 that I ended up >> thinking purely about smaller-than-default masks, but of course this *does* >> matter the other way round. And it is what we've always done on the DT side, >> so at least it makes us consistent. >> >> FWIW I've already started writing up a patch to kill off this bit entirely, >> but either way we still can't meaningfully interpret a supposed DMA limit of >> 0 bits in a table describing DMA-capable devices, so for this patch as a >> fix, >> >> Reviewed-by: Robin Murphy <robin.murphy@arm.com> > > I think there's another issue the comparisons for revision should be > against < 2 not < 1. > > From what I could find DEN0049D (IORT) spec introduced the fields > (curiously the C doc seems to be missing).
I guess it got lost in the documentation system move. FWIW I still have a copy of issue C, and root complex nodes are unchanged at revision 0 there.
> DEN0049B specifies revision as '0', DEN0049C (missing?), DEN0049D > specifies new fields for memory_size_limit and both Named Component and > Root Complex nodes set revision to 2.
My copy of issue D says Root Complex nodes are at revision 1, with memory address size limit added.
(Note that Named Component nodes did bump to rev. 1 in issue C, then to rev. 2 in issue D)
Issue E bumped Root Complex nodes to revision 2 with the addition of the PRI flag, then E.a made a mess of everything by deprecating the revision numbers for individual tables - we probably need to deal with *that*, since otherwise we'll think new tables are back at rev. 0 again, but AFAICS the current check is correct for anything written against the first 5 releases.
Robin.
> so I think it should be: > > if (!node || node->revision < 2) > return -ENODEV; > > Only if we go past this and there is no address limit is it really a > firmware bug. >> >> Thanks, >> Robin. >> >>> } >>> *dma_addr = dmaaddr; >>> > > - Moritz >
| |