From: Thomas Huth <thuth@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>, paulus@samba.org
Cc: michael@ellerman.id.au, benh@kernel.crashing.org,
sjitindarsingh@gmail.com, lvivier@redhat.com,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: [PATCH 01/11] powerpc/kvm: Reserve capabilities and ioctls for HPT resizing
Date: Fri, 16 Dec 2016 10:25:55 +0100 [thread overview]
Message-ID: <25bcced1-4903-2cf7-6a56-14c3ced5cd28@redhat.com> (raw)
In-Reply-To: <20161215055404.29351-2-david@gibson.dropbear.id.au>
On 15.12.2016 06:53, David Gibson wrote:
> This adds a new powerpc-specific KVM_CAP_SPAPR_RESIZE_HPT capability to
> advertise whether KVM is capable of handling the PAPR extensions for
> resizing the hashed page table during guest runtime.
>
> At present, HPT resizing is possible with KVM PR without kernel
> modification, since the HPT is managed within qemu. It's not possible yet
> with KVM HV, because the HPT is managed by KVM. At present, qemu has to
> use other capabilities which (by accident) reveal whether PR or HV is in
> use to know if it can advertise HPT resizing capability to the guest.
>
> To avoid ambiguity with existing kernels, the encoding is a bit odd.
> 0 means "unknown" since that's what previous kernels will return
> 1 means "HPT resize possible if available if and only if the HPT is allocated in
> userspace, rather than in the kernel". Userspace can check
> KVM_CAP_PPC_ALLOC_HTAB to determine if that's the case. In practice
> this will give the same results as userspace's fallback check.
> 2 will mean "HPT resize available and implemented via ioctl()s
> KVM_PPC_RESIZE_HPT_PREPARE and KVM_PPC_RESIZE_HPT_COMMIT"
This encoding IMHO clearly needs some proper documentation in
Documentation/virtual/kvm/api.txt ... and maybe also some dedicated
#defines in an uapi header file.
Thomas
next prev parent reply other threads:[~2016-12-16 9:26 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-15 5:53 [PATCH 00/11] KVM implementation of PAPR HPT resizing extension David Gibson
2016-12-15 5:53 ` [PATCH 01/11] powerpc/kvm: Reserve capabilities and ioctls for HPT resizing David Gibson
2016-12-16 9:25 ` Thomas Huth [this message]
2016-12-19 6:36 ` David Gibson
2016-12-16 13:15 ` Thomas Huth
2016-12-19 6:37 ` David Gibson
2016-12-15 5:53 ` [PATCH 02/11] powerpc/kvm: Rename kvm_alloc_hpt() for clarity David Gibson
2016-12-16 9:03 ` Thomas Huth
2016-12-15 5:53 ` [PATCH 03/11] powerpc/kvm: Gather HPT related variables into sub-structure David Gibson
2016-12-16 9:24 ` Thomas Huth
2016-12-19 0:03 ` David Gibson
2016-12-15 5:53 ` [PATCH 04/11] powerpc/kvm: Don't store values derivable from HPT order David Gibson
2016-12-16 10:39 ` Thomas Huth
2016-12-19 0:04 ` David Gibson
2016-12-15 5:53 ` [PATCH 05/11] powerpc/kvm: Split HPT allocation from activation David Gibson
2016-12-16 11:57 ` Thomas Huth
2016-12-19 0:24 ` David Gibson
2016-12-15 5:53 ` [PATCH 06/11] powerpc/kvm: Allow KVM_PPC_ALLOCATE_HTAB ioctl() to change HPT size David Gibson
2016-12-16 12:44 ` Thomas Huth
2016-12-19 0:48 ` David Gibson
2016-12-19 7:49 ` Thomas Huth
2016-12-19 23:16 ` David Gibson
2016-12-15 5:54 ` [PATCH 07/11] powerpc/kvm: Create kvmppc_unmap_hpte_helper() David Gibson
2016-12-16 12:48 ` Thomas Huth
2016-12-15 5:54 ` [PATCH 08/11] powerpc/kvm: KVM-HV HPT resizing stub implementation David Gibson
2016-12-16 15:35 ` Thomas Huth
2016-12-15 5:54 ` [PATCH 09/11] powerpc/kvm: Outline of KVM-HV HPT resizing implementation David Gibson
2016-12-15 5:54 ` [PATCH 10/11] powerpc/kvm: " David Gibson
2016-12-15 5:54 ` [PATCH 11/11] powerpc/kvm: Advertise availablity of HPT resizing on KVM HV David Gibson
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=25bcced1-4903-2cf7-6a56-14c3ced5cd28@redhat.com \
--to=thuth@redhat.com \
--cc=benh@kernel.crashing.org \
--cc=david@gibson.dropbear.id.au \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=lvivier@redhat.com \
--cc=michael@ellerman.id.au \
--cc=paulus@samba.org \
--cc=sjitindarsingh@gmail.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).