From: Paolo Bonzini <pbonzini@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>, kvm@vger.kernel.org
Cc: Ankur Arora <ankur.a.arora@oracle.com>,
Joao Martins <joao.m.martins@oracle.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Sean Christopherson <seanjc@google.com>,
graf@amazon.com, iaslan@amazon.de, pdurrant@amazon.com,
aagch@amazon.com, fandree@amazon.com, hch@infradead.org
Subject: Re: [PATCH v5 15/16] KVM: Add documentation for Xen hypercall and shared_info updates
Date: Fri, 29 Jan 2021 08:59:14 +0100 [thread overview]
Message-ID: <e7075e1f-672c-f94c-3a3f-b824a45de61d@redhat.com> (raw)
In-Reply-To: <f9b2b4e613ea4e6dd1f253f5092254d121c93c07.camel@infradead.org>
On 28/01/21 20:26, David Woodhouse wrote:
>>> Honestly, I don't even care about reading it out except for long_mode
>>> which the kernel *does* infer for itself when the MSR is used to fill
>>> in the hypercall page.
>>
>> What about VM migration?
>
> The VMM needs to know all these things anyway. It's not like it can
> *forget* where each vCPU's vcpu_info is, then just ask the kernel when
> it's time to orchestrate a migration.
Yeah it may not be particularly useful but it's not hard to write the
code and it's easier to document.
> I suppose *maybe* the upcall vector is an exception; the VMM *could*
> forget that if it really wanted to, then ask the kernel for it on
> migration. But we don't because that seems pointless.
>
> But then it *theoretically* could have a sparse bitmap of "this feature
> but not the next feature", even though that would probably never happen
> in practice without weird selective backports. But it's still an icky
> API. And frankly I could live without the 'get' for any of these except
> LONG_MODE which the kernel might actually flip for us. The rest could
> be write-only for all I care.
I don't think it's that icky, the alternative would be a KVM_GET_ONE_REG
like architecture that just returns a u64 but the bitmap works too.
It's not hard to write the code.
Paolo
next prev parent reply other threads:[~2021-01-29 8:28 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 19:57 [PATCH v5 00/16] KVM: Add minimal support for Xen HVM guests David Woodhouse
2021-01-11 19:57 ` [PATCH v5 01/16] KVM: x86/xen: fix Xen hypercall page msr handling David Woodhouse
2021-01-11 19:57 ` [PATCH v5 02/16] KVM: x86/xen: intercept xen hypercalls if enabled David Woodhouse
2021-01-11 23:42 ` kernel test robot
2021-01-28 12:21 ` Paolo Bonzini
2021-01-11 19:57 ` [PATCH v5 03/16] KVM: x86/xen: Fix coexistence of Xen and Hyper-V hypercalls David Woodhouse
2021-01-11 19:57 ` [PATCH v5 04/16] KVM: x86/xen: add KVM_XEN_HVM_SET_ATTR/KVM_XEN_HVM_GET_ATTR David Woodhouse
2021-01-11 19:57 ` [PATCH v5 05/16] KVM: x86/xen: latch long_mode when hypercall page is set up David Woodhouse
2021-01-11 19:57 ` [PATCH v5 06/16] KVM: x86/xen: add definitions of compat_shared_info, compat_vcpu_info David Woodhouse
2021-01-11 19:57 ` [PATCH v5 07/16] KVM: x86/xen: register shared_info page David Woodhouse
2021-01-11 19:57 ` [PATCH v5 08/16] xen: add wc_sec_hi to struct shared_info David Woodhouse
2021-01-11 19:57 ` [PATCH v5 09/16] KVM: x86/xen: update wallclock region David Woodhouse
2021-01-11 19:57 ` [PATCH v5 10/16] KVM: x86/xen: register vcpu info David Woodhouse
2021-01-11 19:57 ` [PATCH v5 11/16] KVM: x86/xen: setup pvclock updates David Woodhouse
2021-01-11 19:57 ` [PATCH v5 12/16] KVM: x86/xen: register vcpu time info region David Woodhouse
2021-01-11 19:57 ` [PATCH v5 13/16] KVM: x86/xen: register runstate info David Woodhouse
2021-01-28 12:15 ` Paolo Bonzini
2021-01-11 19:57 ` [PATCH v5 14/16] KVM: x86: declare Xen HVM shared info capability and add test case David Woodhouse
2021-01-11 19:57 ` [PATCH v5 15/16] KVM: Add documentation for Xen hypercall and shared_info updates David Woodhouse
2021-01-28 12:18 ` Paolo Bonzini
2021-01-28 16:49 ` David Woodhouse
2021-01-28 17:06 ` Paolo Bonzini
[not found] ` <f9b2b4e613ea4e6dd1f253f5092254d121c93c07.camel@infradead.org>
2021-01-29 7:59 ` Paolo Bonzini [this message]
2021-01-11 19:57 ` [PATCH v5 16/16] KVM: x86/xen: Add event channel interrupt vector upcall David Woodhouse
2021-01-28 12:43 ` Paolo Bonzini
2021-01-28 15:35 ` David Woodhouse
2021-01-28 17:01 ` Paolo Bonzini
2021-01-29 17:33 ` David Woodhouse
2021-01-29 19:19 ` Paolo Bonzini
2021-01-30 13:01 ` David Woodhouse
2021-01-21 11:56 ` [PATCH v5 17/16] KVM: x86/xen: Fix initialisation of gfn caches for Xen shared pages David Woodhouse
2021-01-28 12:45 ` [PATCH v5 00/16] KVM: Add minimal support for Xen HVM guests Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=e7075e1f-672c-f94c-3a3f-b824a45de61d@redhat.com \
--to=pbonzini@redhat.com \
--cc=aagch@amazon.com \
--cc=ankur.a.arora@oracle.com \
--cc=boris.ostrovsky@oracle.com \
--cc=dwmw2@infradead.org \
--cc=fandree@amazon.com \
--cc=graf@amazon.com \
--cc=hch@infradead.org \
--cc=iaslan@amazon.de \
--cc=joao.m.martins@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=pdurrant@amazon.com \
--cc=seanjc@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).