64-bit DMA weirdness

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1

Hey there -

I use a SoundBlaster Live based on the emu10k1 chip; I’ve a stack of 'em so that I can continue to use this card 'til PCI goes away.

I prefer that my MIDI synth do what I tell it to do, and Timidity, FluidSynth and so on don’t; hardware wavetable synthesis rawks.

Anyway, thanks to the DMA addressing scheme on this card using only 31 bits, ever since stepping into the 64-bit world every time I upgrade a kernel I then edit arch/x86/include/asm/dma.h to use 2GB of space rather than 4GB so as to be able to load large soundfonts - an ugly hack, but necessary; I then compile and install this slightly customised kernel. See comment by Thomas Richter at https://bugs.launchpad.net/ubuntu/+source/awesfx/+bug/183456 if you want details.

viz:

I change this:

/* 4GB broken PCI/AGP hardware bus master zone */
#define MAX_DMA32_PFN ((4UL * 1024 * 1024 * 1024) >> PAGE_SHIFT)

to this:
/* 4GB broken PCI/AGP hardware bus master zone */
#define MAX_DMA32_PFN ((2UL * 1024 * 1024 * 1024) >> PAGE_SHIFT)

Seems counterintuitive, but it works - and has for over a decade. However, with 5.3.18-lp152.63 this no longer works; sfxload runs out of memory as though I’d not modified the kernel.

So… I’m running 5.3.18-lp152.60 because it still works, but I weep for the future.

Ideas? Thanks.

2

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3

@bixbyru:

Which Kernel driver are you using?

  • snd-emu10k1 or emu10k1?

AFAICS, only the snd-emu10k1 driver is supplied by default with the Linux Kernel …

Which awesfx package version are you using?

  • Standard – version 0.5.1e
  • multimedia:apps – version 0.5.2
4

I’m using snd-emu… - several drivers.

This is not a driver issue; this is an issue with the 32-bit DMA pool.

Thanks?

5

Oh… and the standard awesfx package.

However and again, this thread regards how the latest (for Leap 15.2) kernel sidesteps the “standard” approach to coddling 31-bit DMA hardware.

Thanks.

6

Try opensuse kernel mailing list.

Also you can try to restrict max memory for your system as suggested on https://www.alsa-project.org/wiki/Matrix:Module-emu10k1

7

You don’t mention which hardware you’re using – AMD or Intel?

As a thought – is the hardware using UEFI and, have you enabled UEFI Secure Boot?

  • I’m wondering if the “Kernel Lockdown” which arrived with Leap 15.2 for the case of UEFI Secure Boot, is messing up the 31-bit DMA addressing …
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'K; I’ll give that a whirl.

9

Intel, dual Xeon; I use a server as my deskside computer because it’s indestructible, my data is safe and so on, and since I’m not a gamer it has more’n enough horsepower for my needs. Old HP Proliant ML370, from the mid-Shrubbya years and well before the onset of UEFI.

The “kernel lockdown” didn’t mess with me with 5.3.18-lp152.60, but still that provokes a “Hmmm…”

Thanks for the replies; please keep 'em coming.

10

Hi
Just making it a bit more robust against proprietary drivers that are not at least dual license… a win win… :wink:

11

Well, the tips at alsa-project.org outlined exactly what I’ve been doing - and what stopped working; editing the kernel, that is; trying to run in 2 GB is a nonstarter, as that’d be akin to “running” whilst wearing cement overshoes.

What did they do that’s ewscraying with me, why, and HOW…?!?