Re: hvmloader - allow_memory_relocate overlaps

[Jan Beulich <jbeulich@xxxxxxxx>]

On 01.03.2024 21:24, Neowutran wrote:
> On 2024-02-07 16:02, Jan Beulich wrote:
>> Could you give the patch below a try? I don't have a device with large
>> enough a BAR that I could sensibly pass through to a guest, so I was
>> only able to build-test the change.
> 
> Hi and thanks,
> I just tested it, it indeed work well when the GPU have bar > 1Go. 
> 
> ------------
> Setup: 
> I removed my patch 
> (
> 
> 
> --- a/tools/libs/light/libxl_dm.c
> +++ b/tools/libs/light/libxl_dm.c
> @@ -2431,6 +2431,10 @@ void libxl__spawn_stub_dm(libxl__egc *egc, 
> libxl__stub_dm_spawn_state *sdss)
>                                         libxl__xs_get_dompath(gc, 
> guest_domid)),
>                          "%s",
>                          
> libxl_bios_type_to_string(guest_config->b_info.u.hvm.bios));
> +        libxl__xs_printf(gc, XBT_NULL,
> +                         libxl__sprintf(gc, 
> "%s/hvmloader/allow-memory-relocate", libxl__xs_get_dompath(gc, guest_domid)),
> +                         "%d",
> +                         0);
>      }
>      ret = xc_domain_set_target(ctx->xch, dm_domid, guest_domid);
>      if (ret<0) {
> 
> 
> )
> and applied your suggested "skip huge BARs" patch. 
> My GPU: nvidia 4080
> -------------
> 
> When the option "Resizable BAR support" is activated in my bios,
> the BAR1 size of my gpu is reported to be 16GB. With this patch, gpu
> passthrough work. 

Good. I guess I should properly post that patch then, no matter that ...

> When the option "Resizable BAR support" is desactivated in my bios,
> the BAR1 size of my gpu is reported to be 256MB. With this patch,
> gpu passthrough doesn't work (same crash as before)

... this clearly requires further work then. 256Mb isn't all that large;
could you post a log file (fragment) for this very case?

> ( note: the option "Resizable BAR support" may or may not exist
> depending on the motherboard model, on some it is 'hardcoded' to
> activated, on some it is 'hardcoded' to desactivated)

Resizable BARs is yet another thing on my (and maybe also Roger's) todo
list. I'm a little uncomfortable doing any work there without having a
system where I could actually test it ...

Jan