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

[Gordan Bobic <gordan@bobich.net>]

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?
>
> 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