Update powerpc busdma to handle unmapped/out-of-context buffers

[jah]

Summary

Use pmap_quick* to handle bouncing of unmapped buffers. Also treat usermode buffers as unmapped, to avoid borrowing the UVA for copies. This allows sync'ing usermode buffers outside the context of the owning process, and sync'ing bounced maps in non-sleepable contexts.

This is equivalent to r286787 for x86.

[jah]

Remove unclear comment on PHYS_TO_VM_PAGE().
Noted by: avg

[jhibbits]

Code looks fine. I won't have time to test for a while, so want a second opinion.

[jah]

This one's been sitting for a while. Anything I can do to test this out on my own? qemu maybe?

[jhibbits]

I think qemu can boot powerpc64 (see https://wiki.freebsd.org/QemuRecipes ). What kinds of testing should be done? I have a Book-E board I could boot test with, and do basic SATA I/O, would that be enough? I also have some PowerMac hardware. Would need a week or two before I can test with that though.

[jah]

In D3989#135429, @jhibbits wrote:

I think qemu can boot powerpc64 (see https://wiki.freebsd.org/QemuRecipes ). What kinds of testing should be done? I have a Book-E board I could boot test with, and do basic SATA I/O, would that be enough? I also have some PowerMac hardware. Would need a week or two before I can test with that though.

A week or two is no problem.
The busdma logic here is basically the same as x86, so the big risk is that I got something wrong in the powerpc implementation of pmap_quick_enter_page. Would SATA or network I/O end up bouncing on either qemu or your hardware?

[jhibbits]

A week or two is no problem.
The busdma logic here is basically the same as x86, so the big risk is that I got something wrong in the powerpc implementation of pmap_quick_enter_page. Would SATA or network I/O end up bouncing on either qemu or your hardware?

Reading the busdma_machdep source, it looks as though it'll bounce if the lowaddr of the created tag, or an alignment > 1, so probably similar to how x86 bounces. It looks like I can test on my book-e hardware, which uses my new fsl_sata driver (lowaddr of BUS_SPACE_MAXADDR_32BIT, on a machine with 6GB RAM). Network traffic might do it on qemu as well.

[jhibbits]

Did some light testing, but not sure if I triggered anything.

[jah]

In D3989#151738, @jhibbits wrote:

Did some light testing, but not sure if I triggered anything.

Thanks for testing it!
I also have a simple kmod at https://reviews.freebsd.org/D3014 just for testing pmap_quick_enter_page(). The difference between x86 and ppc implementations of that function is the real risk in this change, since the busdma code is basically the same as x86 (or at least as x86 used to be before some recent xen-related changes).

I haven't had any luck w/ ppc64 on qemu yet. 11.0-beta2 iso hangs while loading the kernel. I've also tried to create a custom disk image the way I do for mips (https://wiki.freebsd.org/FreeBSD/MipsEmulation) but that gets me a weird-looking exception from OFW when it tries to load the kernel.