Re: [GIT preview] for-6.3/cxl-ram-region

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 30 Jan 2023 09:23:54 -0500
Gregory Price <gregory.price@memverge.com> wrote:

> On Thu, Jan 26, 2023 at 07:34:24PM +0000, Jonathan Cameron wrote:
> > Looks like decoders are programmed correctly as I can read and write from
> > the HPA using devmem2.
> > 
> > This is against http://gitlab.com/jic23/qemu cxl-2023-01-26 which has been
> >   
> 
> Johnathan, can you explain how you're accessing the memory? I don't
> quite follow.

Command sequence is pretty similar to yours (not checked it's identical)
and once commit is done, using a version of devmem2 (not sure it was this one)
https://github.com/hackndev/tools/blob/master/devmem2.c 
(if you want 64 bit read / write add the obvious additional parameter ;)

with appropriately loose kernel configuration that /dev/mem works

Then run that against addresses starting at the bottom of the CFMWS
HPA range to read and write.  It's a hack but proves the routing etc
is all setup correctly.

I had this lying around from testing the region setup code when it
was in a similar partial state to this support.

Jonathan


> 
> Extra Notes
> 1) Tested against Jonathan's QEMU 01-26 branch above
> 2) Tested w/ the Linux preview branch rebased on top of the DOE fixes
>    that were causing other bugs.