From: Andrii Anisov <andrii.anisov@gmail.com>
To: Julien Grall <julien.grall@arm.com>, xen-devel@lists.xen.org
Cc: "Juergen Gross" <jgross@suse.com>,
"Andrii Anisov" <andrii_anisov@epam.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH 0/2 for-4.12] Introduce runstate area registration with phys address
Date: Thu, 7 Mar 2019 15:01:45 +0200 [thread overview]
Message-ID: <be2b4a60-d70d-9d28-d638-1a7fd11f0578@gmail.com> (raw)
In-Reply-To: <c3a5728c-6425-29f9-8e5c-7b6da1f729ce@arm.com>
Dear Julien,
On 05.03.19 15:56, Julien Grall wrote:
> I had some concern about this solution in [1] that have not been addressed nor even mentioned in the series.
You missed the link.
So I assume you say about you preferences to not have runstate area mapped because of consuming vmap space for arm64. Also, along that thread you mentioned you that guest might change gva mapping, what is irrelevant to registration with physical address.
My reasons to have that runstate mapped are following:
- Introducing the new interface we are not burden with legacy, so in charge to impose requirements. In this case - to have runstate area not crossing a page boundary
- Global mapping used here does not consume vmap space on arm64. It seems to me x86 guys are ok with mapping as well, at least Roger suggested it from the beginning. So it should be ok for them as well.
- In case domain is mapping runstate with physical address, it can not change the mapping.
- I suppose, normally, runstate area would be registered once per vcpu. While it is updated each context switch, I do estimate it more optimal to have it mapped once on registration. This reduces two mappings per context switch in the worst case (one for prev vcpu, one for the next).
- IMHO, this implementation is simpler and cleaner than what I have for runstate mapping on access.
So, taking in account all above, I really do not see, how runstate area registered with physical address differs from vcpu_info and does not deserve to be permanently mapped.
--
Sincerely,
Andrii Anisov.
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next prev parent reply other threads:[~2019-03-07 13:01 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-05 13:14 [PATCH 0/2 for-4.12] Introduce runstate area registration with phys address Andrii Anisov
2019-03-05 13:14 ` [PATCH 1/2 for-4.12] xen: introduce VCPUOP_register_runstate_phys_memory_area hypercall Andrii Anisov
2019-03-14 8:45 ` Jan Beulich
2019-03-05 13:14 ` [PATCH 2/2 for-4.12] xen: implement VCPUOP_register_runstate_phys_memory_area Andrii Anisov
2019-03-14 9:05 ` Jan Beulich
2019-03-05 13:20 ` [PATCH 0/2 for-4.12] Introduce runstate area registration with phys address Juergen Gross
2019-03-05 13:32 ` Andrii Anisov
2019-03-05 13:39 ` Julien Grall
2019-03-05 14:11 ` Andrii Anisov
2019-03-05 14:30 ` Julien Grall
2019-03-07 13:07 ` Andrii Anisov
2019-03-05 13:44 ` Juergen Gross
2019-03-05 13:50 ` Andrii Anisov
2019-03-05 13:56 ` Julien Grall
2019-03-07 13:01 ` Andrii Anisov [this message]
2019-03-07 14:02 ` Julien Grall
2019-03-07 14:34 ` Andrii Anisov
2019-03-07 15:17 ` Julien Grall
2019-03-07 15:20 ` Julien Grall
2019-03-07 16:16 ` Roger Pau Monné
2019-03-07 16:36 ` Julien Grall
2019-03-07 17:15 ` Roger Pau Monné
2019-03-07 18:00 ` Julien Grall
2019-03-08 6:28 ` Juergen Gross
2019-03-08 10:15 ` Julien Grall
2019-03-08 10:18 ` Juergen Gross
2019-03-08 10:31 ` Julien Grall
2019-03-18 11:31 ` Andrii Anisov
2019-03-18 12:25 ` Julien Grall
2019-03-18 13:38 ` Andrii Anisov
2019-03-21 19:05 ` Julien Grall
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