Re: [Xen-devel] Max gfn?

[AP <apxeng@xxxxxxxxx>]

On Mon, Mar 12, 2012 at 12:31 PM, AP <apxeng@xxxxxxxxx> wrote:
> On Thu, Mar 8, 2012 at 11:25 PM, Keir Fraser <keir@xxxxxxx> wrote:
>> On 09/03/2012 05:56, "AP" <apxeng@xxxxxxxxx> wrote:
>>
>>> I have a 12GB 64-bit Linux HVM guest (CentOS 5.5). When I look at the
>>> e820 map in the guest, I see the following:
>>>
>>> BIOS-provided physical RAM map:
>>>  BIOS-e820: 0000000000010000 - 000000000009e000 (usable)
>>>  BIOS-e820: 000000000009e000 - 00000000000a0000 (reserved)
>>>  BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
>>>  BIOS-e820: 0000000000100000 - 00000000f0000000 (usable)
>>>  BIOS-e820: 00000000fc000000 - 0000000100000000 (reserved)
>>>  BIOS-e820: 0000000100000000 - 000000030f000000 (usable)
>>>
>>> I see that the highest usable gpa is over 12GB due to the reserved
>>> slots and the max gfn is 30f000.  If I use xc_domain_getinfolist() and
>>> look at max_pages, it returns 300100 which correctly reflects 12GB.
>>> But is there a way for me to find out the max gfn that is reflected in
>>> the guest using libxc?
>>
>> xc_domain_maximum_gpfn() returns a value guaranteed to be >= the current
>> maximum gpfn in the guests physical address space.
>
> Thank you, that worked. What I am actually doing is passing it as a
> parameter to xc_hvm_set_mem_access(), to set all of guest memory to a
> certain mem_access type. Now for a 512MB VM, xc_domain_maximum_gpfn()
> returns 0xfffff. If I pass that value to xc_hvm_set_mem_access() it
> returns -1. However with 1GB, 2GB, 3GB VMs, xc_domain_maximum_gpfn()
> returns 0xfffff but the xc_hvm_set_mem_access() goes through. Any idea
> why the discrepancy with 512MB VMs?

The error occurs in HVMOP_set_mem_access on the set_entry call to
0x9dc00 gpfn. I still don't understand why this is an issue only with
512MB VMs.

> Thanks,
> AP
>
>>
>>  -- Keir
>>
>>> Thanks,
>>> AP
>>>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxx
>>> http://lists.xen.org/xen-devel
>>
>>

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