From: Jan Beulich <jbeulich@suse.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH for-4.19? 1/2] xen/x86: account for max guest gfn and number of foreign mappings in the p2m
Date: Mon, 6 May 2024 17:34:59 +0200 [thread overview]
Message-ID: <a2c6ca3c-4d34-4423-bfb2-13bb98dff56e@suse.com> (raw)
In-Reply-To: <Zjj4SQ3r9ZtjjjKn@macbook>
On 06.05.2024 17:33, Roger Pau Monné wrote:
> On Mon, May 06, 2024 at 12:07:33PM +0200, Jan Beulich wrote:
>> On 30.04.2024 18:58, Roger Pau Monne wrote:
>>> Keep track of the maximum gfn that has ever been populated into the p2m, and
>>> also account for the number of foreign mappings. Such information will be
>>> needed in order to remove foreign mappings during teardown for HVM guests.
>>
>> Is "needed" the right term? We could e.g. traverse the P2M tree (didn't look
>> at patch 2 yet as to how exactly you use these two new fields there), at which
>> point we might get away without either or both of these extra statistics,
>> while at the same time also not needing to iterate over a gigantic range of
>> GFNs. Going from populated page tables would roughly match "max_gfn", with the
>> benefit of certain removals of P2M entries then also shrinking the upper bound.
>
> One note about traversing the p2m tree that I forgot to add earlier:
> AFAICT we would need one implementation for EPT and one for NPT, as I
> expect the different page-table format won't allow us to use the same
> code against both EPT and NPT page-tables (I really need to check).
Yes, that would be pretty much unavoidable, I agree.
Jan
next prev parent reply other threads:[~2024-05-06 15:35 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 16:58 [PATCH for-4.19? 0/2] xen/x86: support foreign mappings for HVM Roger Pau Monne
2024-04-30 16:58 ` [PATCH for-4.19? 1/2] xen/x86: account for max guest gfn and number of foreign mappings in the p2m Roger Pau Monne
2024-05-06 10:07 ` Jan Beulich
2024-05-06 14:32 ` Roger Pau Monné
2024-05-06 14:55 ` Jan Beulich
2024-05-06 15:13 ` Roger Pau Monné
2024-05-06 15:33 ` Roger Pau Monné
2024-05-06 15:34 ` Jan Beulich [this message]
2024-04-30 16:58 ` [PATCH for-4.19? 2/2] xen/x86: remove foreign mappings from the p2m on teardown Roger Pau Monne
2024-05-06 10:41 ` Jan Beulich
2024-05-06 14:56 ` Roger Pau Monné
2024-05-02 8:50 ` [PATCH for-4.19? 0/2] xen/x86: support foreign mappings for HVM Oleksii
2024-05-03 13:10 ` Roger Pau Monné
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