Re: [Xen-devel] HVM support for e820_host (Was: Bug: Limitation of <=2GB RAM in domU persists with 4.3.0)

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Sep 03, 2013 at 10:24:44PM +0100, Gordan Bobic wrote:
> On 09/03/2013 10:10 PM, Konrad Rzeszutek Wilk wrote:
> >On Tue, Sep 03, 2013 at 09:49:40PM +0100, Gordan Bobic wrote:
> >>I spoke too soon - even with e820_host=0, the same error occurs.
> >>What did I break? The code in question is this:
> >>
> >>if (libxl_defbool_val(d_config->b_info.e820_host)) {
> >>     ret = libxl__e820_alloc(gc, domid, d_config);
> >>     if (ret) {
> >>         LIBXL__LOG_ERRNO(gc->owner, LIBXL__LOG_ERROR,
> >>                 "Failed while collecting E820 with: %d (errno:%d)\n",
> >>                 ret, errno);
> >>     }
> >>}
> >>
> >>With e820_host=0, that outer black should evaluate to false, should
> >>it not? In libxl_create.c, if I am understanding the code correctly,
> >>e820_host is defaulted to false, too. What am I missing?

Does your config have 'pci' in it? The patch you sent had this:

+        if (d_config->num_pcidevs)
+            libxl_defbool_set(&b_info->e820_host, true);

Which means that even if you did not have e820_host it will be automatically
set if you have PCI devices.

> >
> >Just sent you an email but I believe what is failing is:
> >
> >241     rc = xc_domain_set_memory_map(ctx->xch, domid, map, nr);
> 
> But with e820_host=0 set in the config, libxl__e820_alloc() should
> not be getting called in the first place. That function only gets
> called from line 303, inside that if block I pasted above. That is
> what is puzzling me.
> 
> >You can add some extra LIBXL__LOG_ERRNO to check each 'rc' to see
> >which one of them failed.
> >
> >Hm, perhaps it might make sense to actually have the libxl__e820_alloc
> >also use the LIBXL__LOG_ERRNO to log more details..
> 
> OK, I'll add some debug and see what I find.
> 
> Gordan

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