The below results in an accurate TSC measurement when forced on a IVB: If, for some reason, the TSC init has to fall back to TSC calibration, itĪllow TSC calibration to reliably fall back to HPET. Part of the problem is that that machine doesn't have Zhang Rui reported that a Surface Pro 4 will fail to boot with ` (155 subsequent siblings) 156 siblings, 0 replies 275+ messages in threadĬc: Peter Zijlstra, Thomas Gleixner, len.brown, rui.zhang, Sasha Levin 0:19 ` NFSv4: always set NFS_LOCK_LOST when a lock is lost Sasha Levin 0:19 firewire-ohci: work around oversized DMA reads on JMicron controllers Sasha 0:19 ` Sasha Levin * x86/tsc: Allow TSC calibration without PIT ^ raw reply related 275+ messages in thread + desc->buffer_size = PAGE_SIZE - offset - 0x10 + * Work around this by always leaving at least 0x10 bytes of padding. + * an IOMMU is in use and the oversized read crosses a page boundary. + * for descriptors, even 0x10-byte ones. + * Some controllers, like JMicron ones, always issue 0x20-byte DMA reads desc->buffer_size = PAGE_SIZE - offset Offset = (void *)&desc->buffer - (void *)desc Unconditionally for controllers in case others have the same behavior.ġ file changed, 7 insertions(+), 1 deletion(-)ĭiff -git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c The end of descriptor buffer pages, which should be harmless to do This works around the problem by always leaving 0x10 padding bytes at This is often harmless, butĬan cause page faults on modern systems with IOMMUs:ĭMAR: Request device fault addr fff56000 PTE Read access is not setįirewire_ohci 0000:05:00.0: DMA context IT0 has stopped, error code: evt_descriptor_read To: stable, linux-kernel +Cc: Hector Martin, Stefan Richter, Sasha LevinĪt least some JMicron controllers issue buggy oversized DMA reads whenįetching context descriptors, always fetching 0x20 bytes at once forĭescriptors which are only 0x10 bytes long.

` (156 more replies) 0 siblings, 157 replies 275+ messages in thread 0:19 ` x86/tsc: Allow TSC calibration without PIT Sasha Levin Firewire-ohci: work around oversized DMA reads on JMicron controllers archive mirror help / color / mirror / Atom feed * firewire-ohci: work around oversized DMA reads on JMicron controllers 0:19 Sasha Levin

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