Now that 3.4 is out, if you want these patches checked in then please
re-send with changeset comments and signed-off-by lines.
Thanks,
Keir
On 19/03/2009 08:07, "Huang2, Wei" <Wei.Huang2@xxxxxxx> wrote:
> Here are patches using the middle approach. It handles 1GB pages in PoD
> by remapping 1GB with 2MB pages & retry. I also added code for 1GB
> detection. Please comment.
>
> Thanks a lot,
>
> -Wei
>
> -----Original Message-----
> From: dunlapg@xxxxxxxxx [mailto:dunlapg@xxxxxxxxx] On Behalf Of George
> Dunlap
> Sent: Wednesday, March 18, 2009 12:20 PM
> To: Huang2, Wei
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; keir.fraser@xxxxxxxxxxxxx; Tim Deegan
> Subject: Re: [Xen-devel] [RFC][Patches] Xen 1GB Page Table Support
>
> Thanks for doing this work, Wei -- especially all the extra effort for
> the PoD integration.
>
> One question: How well would you say you've tested the PoD
> functionality? Or to put it the other way, how much do I need to
> prioritize testing this before the 3.4 release?
>
> It wouldn't be a bad idea to do as you suggested, and break things
> into 2 meg pages for the PoD case. In order to take the best
> advantage of this in a PoD scenario, you'd need to have a balloon
> driver that could allocate 1G of continuous *guest* p2m space, which
> seems a bit optimistic at this point...
>
> -George
>
> 2009/3/18 Huang2, Wei <Wei.Huang2@xxxxxxx>:
>> Current Xen supports 2MB super pages for NPT/EPT. The attached patches
>> extend this feature to support 1GB pages. The PoD (populate-on-demand)
>> introduced by George Dunlap made P2M modification harder. I tried to
>> preserve existing PoD design by introducing a 1GB PoD cache list.
>>
>>
>>
>> Note that 1GB PoD can be dropped if we don't care about 1GB when PoD
> is
>> enabled. In this case, we can just split 1GB PDPE into 512x2MB PDE
> entries
>> and grab pages from PoD super list. That can pretty much make
>> 1gb_p2m_pod.patch go away.
>>
>>
>>
>> Any comment/suggestion on design idea will be appreciated.
>>
>>
>>
>> Thanks,
>>
>>
>>
>> -Wei
>>
>>
>>
>>
>>
>> The following is the description:
>>
>> === 1gb_tools.patch ===
>>
>> Extend existing setup_guest() function. Basically, it tries to
> allocate 1GB
>> pages whenever available. If this request fails, it falls back to 2MB.
> If
>> both fail, then 4KB pages will be used.
>>
>>
>>
>> === 1gb_p2m.patch ===
>>
>> * p2m_next_level()
>>
>> Check PSE bit of L3 page table entry. If 1GB is found (PSE=1), we
> split 1GB
>> into 512 2MB pages.
>>
>>
>>
>> * p2m_set_entry()
>>
>> Configure the PSE bit of L3 P2M table if page order == 18 (1GB).
>>
>>
>>
>> * p2m_gfn_to_mfn()
>>
>> Add support for 1GB case when doing gfn to mfn translation. When L3
> entry is
>> marked as POPULATE_ON_DEMAND, we call 2m_pod_demand_populate().
> Otherwise,
>> we do the regular address translation (gfn ==> mfn).
>>
>>
>>
>> * p2m_gfn_to_mfn_current()
>>
>> This is similar to p2m_gfn_to_mfn(). When L3 entry s marked as
>> POPULATE_ON_DEMAND, it demands a populate using
> p2m_pod_demand_populate().
>> Otherwise, it does a normal translation. 1GB page is taken into
>> consideration.
>>
>>
>>
>> * set_p2m_entry()
>>
>> Request 1GB page
>>
>>
>>
>> * audit_p2m()
>>
>> Support 1GB while auditing p2m table.
>>
>>
>>
>> * p2m_change_type_global()
>>
>> Deal with 1GB page when changing global page type.
>>
>>
>>
>> === 1gb_p2m_pod.patch ===
>>
>> * xen/include/asm-x86/p2m.h
>>
>> Minor change to deal with PoD. It separates super page cache list into
> 2MB
>> and 1GB lists. Similarly, we record last gpfn of sweeping for both 2MB
> and
>> 1GB.
>>
>>
>>
>> * p2m_pod_cache_add()
>>
>> Check page order and add 1GB super page into PoD 1GB cache list.
>>
>>
>>
>> * p2m_pod_cache_get()
>>
>> Grab a page from cache list. It tries to break 1GB page into 512 2MB
> pages
>> if 2MB PoD list is empty. Similarly, 4KB can be requested from super
> pages.
>> The breaking order is 2MB then 1GB.
>>
>>
>>
>> * p2m_pod_cache_target()
>>
>> This function is used to set PoD cache size. To increase PoD target,
> we try
>> to allocate 1GB from xen domheap. If this fails, we try 2MB. If both
> fail,
>> we try 4KB which is guaranteed to work.
>>
>>
>>
>> To decrease the target, we use a similar approach. We first try to
> free 1GB
>> pages from 1GB PoD cache list. If such request fails, we try 2MB PoD
> cache
>> list. If both fail, we try 4KB list.
>>
>>
>>
>> * p2m_pod_zero_check_superpage_1gb()
>>
>> This adds a new function to check for 1GB page. This function is
> similar to
>> p2m_pod_zero_check_superpage_2mb().
>>
>>
>>
>> * p2m_pod_zero_check_superpage_1gb()
>>
>> We add a new function to sweep 1GB page from guest memory. This is the
> same
>> as p2m_pod_zero_check_superpage_2mb().
>>
>>
>>
>> * p2m_pod_demand_populate()
>>
>> The trick of this function is to do remap_and_retry if
> p2m_pod_cache_get()
>> fails. When p2m_pod_get() fails, this function will splits p2m table
> entry
>> into smaller ones (e.g. 1GB ==> 2MB or 2MB ==> 4KB). That can
> guarantee
>> populate demands always work.
>>
>>
>>
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
>>
>>
>
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