On 06.03.2020 14:45, Paul Durrant wrote:
>> -----Original Message-----
>> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of Jan
>> Beulich
>> Sent: 06 March 2020 13:39
>> To: Durrant, Paul <pdurr...@amazon.co.uk>
>> Cc: xen-devel@lists.xenproject.org; Andrew Cooper
>> <andrew.coop...@citrix.com>; Wei Liu <w...@xen.org>;
>> pdurr...@amzn.com; Roger Pau Monné <roger....@citrix.com>
>> Subject: Re: [Xen-devel] [PATCH v3 3/6] x86 / pv: do not treat PGC_extra
>> pages as RAM when
>> constructing dom0
>>
>> On 06.03.2020 13:03, Durrant, Paul wrote:
>>>> -----Original Message-----
>>>> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of Jan
>>>> Beulich
>>>> Sent: 06 March 2020 11:56
>>>> To: pdurr...@amzn.com
>>>> Cc: xen-devel@lists.xenproject.org; Durrant, Paul <pdurr...@amazon.co.uk>;
>>>> Roger Pau Monné
>>>> <roger....@citrix.com>; Wei Liu <w...@xen.org>; Andrew Cooper
>>>> <andrew.coop...@citrix.com>
>>>> Subject: Re: [Xen-devel] [PATCH v3 3/6] x86 / pv: do not treat PGC_extra
>>>> pages as RAM when
>>>> constructing dom0
>>>>
>>>> On 05.03.2020 13:45, pdurr...@amzn.com wrote:
>>>>> --- a/xen/arch/x86/pv/dom0_build.c
>>>>> +++ b/xen/arch/x86/pv/dom0_build.c
>>>>> @@ -792,6 +792,10 @@ int __init dom0_construct_pv(struct domain *d,
>>>>> {
>>>>> mfn = mfn_x(page_to_mfn(page));
>>>>> BUG_ON(SHARED_M2P(get_gpfn_from_mfn(mfn)));
>>>>> +
>>>>> + if ( page->count_info & PGC_extra )
>>>>> + continue;
>>>>
>>>> This surely is a pattern, i.e. there are more similar changes to
>>>> make: tboot_gen_domain_integrity() e.g. ignores d->xenpage_list,
>>>> and hence with the goal of converting the shared info page would
>>>> also want adjustment. For dump_numa() it may be less important,
>>>> but it would still look more correct if it too got changed.
>>>> audit_p2m() might apparently complain about such pages (and
>>>> hence might be a problem with the one PGC_extra page VMX domains
>>>> now have). And this is only from me looking at
>>>> page_list_for_each(..., &d->page_list) constructs; who knows
>>>> what else there is.
>>>>
>>>
>>> Those are dealt with by the is_special_page() patch later on I think.
>>
>> Having already looked at that patch as well - I don't think so, no.
>> That one only replaces uses of is_xen_heap_page(), but doesn't add
>> any checks where such uses simply aren't needed because code is
>> looking at ->page_list only.
>
> Well, I did say:
>
> "It didn't seem appropriate to use that macro here though since we
> know pages on the page list cannot be xenheap pages."
And I agree and understand.
> i.e. an open coded check here seems like the right thing to do.
Indeed.
> If I've missed other places where I need to account for pages which
> are specifically PGC_extra pages then I'll need to fix them similarly.
Yes please. Thanks.
Jan
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