From: Paolo Bonzini <pbonzini@redhat.com>
To: Ben Gardon <bgardon@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
Peter Xu <peterx@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Peter Shier <pshier@google.com>,
Junaid Shahid <junaids@google.com>,
Jim Mattson <jmattson@google.com>,
Yulei Zhang <yulei.kernel@gmail.com>,
Wanpeng Li <kernellwp@gmail.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Xiao Guangrong <xiaoguangrong.eric@gmail.com>
Subject: Re: [PATCH 5/6] KVM: x86/mmu: Protect kvm->memslots with a mutex
Date: Wed, 28 Apr 2021 23:41:47 +0200 [thread overview]
Message-ID: <5b4a0c30-118c-da1f-281c-130438a1c833@redhat.com> (raw)
In-Reply-To: <CANgfPd9kVJOAR_uq+oh9kE2gr00EUAGSPiJ9jMR9BdG2CAC+BA@mail.gmail.com>
On 28/04/21 22:40, Ben Gardon wrote:
> ... However with the locking you propose below, we might still run
> into issues on a move or delete, which would mean we'd still need the
> separate memory allocation for the rmaps array. Or we do some
> shenanigans where we try to copy the rmap pointers from the other set
> of memslots.
If that's (almost) as easy as passing old to
kvm_arch_prepare_memory_region, that would be totally okay.
> My only worry is the latency this could add to a nested VM launch, but
> it seems pretty unlikely that that would be frequently coinciding with
> a memslot change in practice.
Right, memslot changes in practice occur only at boot and on hotplug.
If that was a problem we could always make the allocation state
off/in-progress/on, allowing to check the allocation state out of the
lock. This would only potentially slow down the first nested VM launch.
Paolo
next prev parent reply other threads:[~2021-04-28 21:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 22:36 [PATCH 0/6] Lazily allocate memslot rmaps Ben Gardon
2021-04-27 22:36 ` [PATCH 1/6] KVM: x86/mmu: Track if shadow MMU active Ben Gardon
2021-04-27 22:36 ` [PATCH 2/6] KVM: x86/mmu: Skip rmap operations if shadow MMU inactive Ben Gardon
2021-04-27 22:36 ` [PATCH 3/6] KVM: x86/mmu: Deduplicate rmap freeing in allocate_memslot_rmap Ben Gardon
2021-04-28 10:00 ` Paolo Bonzini
2021-04-28 16:23 ` Ben Gardon
2021-04-27 22:36 ` [PATCH 4/6] KVM: x86/mmu: Factor out allocating memslot rmap Ben Gardon
2021-04-27 22:36 ` [PATCH 5/6] KVM: x86/mmu: Protect kvm->memslots with a mutex Ben Gardon
2021-04-28 6:25 ` Paolo Bonzini
2021-04-28 16:40 ` Ben Gardon
2021-04-28 17:46 ` Paolo Bonzini
2021-04-28 20:40 ` Ben Gardon
2021-04-28 21:41 ` Paolo Bonzini [this message]
2021-04-28 21:46 ` Ben Gardon
2021-04-28 23:42 ` Paolo Bonzini
2021-04-29 0:40 ` Sean Christopherson
2021-04-29 1:42 ` Sean Christopherson
2021-04-29 7:02 ` Paolo Bonzini
2021-04-29 17:45 ` Ben Gardon
2021-04-27 22:36 ` [PATCH 6/6] KVM: x86/mmu: Lazily allocate memslot rmaps Ben Gardon
2021-04-28 10:03 ` Paolo Bonzini
2021-04-28 16:45 ` Ben Gardon
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=5b4a0c30-118c-da1f-281c-130438a1c833@redhat.com \
--to=pbonzini@redhat.com \
--cc=bgardon@google.com \
--cc=jmattson@google.com \
--cc=junaids@google.com \
--cc=kernellwp@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=peterx@redhat.com \
--cc=pshier@google.com \
--cc=seanjc@google.com \
--cc=vkuznets@redhat.com \
--cc=xiaoguangrong.eric@gmail.com \
--cc=yulei.kernel@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).