Re: [Xen-devel] Question about xenpage_list

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.08.2019 17:51, Tamas K Lengyel wrote:
> On Wed, Aug 28, 2019 at 9:35 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>
>> On 28.08.2019 17:28, Tamas K Lengyel wrote:
>>> Hi all,
>>> I'm trying to track down how a call in common/grant_table.c to
>>> share_xen_page_with_guest will actually populate that page into the
>>> guest's physmap. Immediately after the call the page doesn't seem to
>>> be present in the physmap, as share_xen_page_with_guest will just add
>>> the page to the domain's xenpage_list linked-list:
>>>
>>>         unsigned long mfn;
>>>         unsigned long gfn;
>>>
>>>         share_xen_page_with_guest(virt_to_page(gt->shared_raw[i]), d, 
>>> SHARE_rw);
>>>
>>>         mfn = virt_to_mfn(gt->shared_raw[i]);
>>>         gfn = mfn_to_gmfn(d, mfn);
>>>
>>>         gdprintk(XENLOG_INFO, "Sharing %lx -> %lx with domain %u\n",
>>> gfn, mfn, d->domain_id);
>>>
>>> This results in the following:
>>>
>>> (XEN) grant_table.c:1820:d0v0 Sharing ffffffffffffffff -> 42c71e with 
>>> domain 1
>>>
>>> AFAICT the page only gets populated into the physmap once the domain
>>> gets unpaused. If I let the domain run and then pause it I can see
>>> that the page is in the guest's physmap (by looping through all the
>>> entries in its EPT):
>>>
>>> (XEN) mem_sharing.c:1636:d0v0 0xf2000 -> 0x42c71e is a grant mapping
>>> shared with the guest
>>
>> This should be the result of the domain having made a respective
>> XENMAPSPACE_grant_table request, shouldn't it?
>>
> 
> Do you mean the guest itself or the toolstack?

The guest itself - how would the tool stack know where to put the
frame(s)?

Jan

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