KVM Archive on lore.kernel.org
 help / color / Atom feed
From: Andy Lutomirski <luto@kernel.org>
To: Nadav Amit <namit@vmware.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH 6/9] KVM: x86: Provide paravirtualized flush_tlb_multi()
Date: Tue, 25 Jun 2019 20:35:12 -0700
Message-ID: <CALCETrWcUWw8ep-n6RaOeojnL924xOM7g7eb9g=3DRwOHQAgnA@mail.gmail.com> (raw)
In-Reply-To: <401C4384-98A1-4C27-8F71-4848F4B4A440@vmware.com>

On Tue, Jun 25, 2019 at 7:39 PM Nadav Amit <namit@vmware.com> wrote:
>
> > On Jun 25, 2019, at 2:40 PM, Dave Hansen <dave.hansen@intel.com> wrote:
> >
> > On 6/12/19 11:48 PM, Nadav Amit wrote:
> >> Support the new interface of flush_tlb_multi, which also flushes the
> >> local CPU's TLB, instead of flush_tlb_others that does not. This
> >> interface is more performant since it parallelize remote and local TLB
> >> flushes.
> >>
> >> The actual implementation of flush_tlb_multi() is almost identical to
> >> that of flush_tlb_others().
> >
> > This confused me a bit.  I thought we didn't support paravirtualized
> > flush_tlb_multi() from reading earlier in the series.
> >
> > But, it seems like that might be Xen-only and doesn't apply to KVM and
> > paravirtualized KVM has no problem supporting flush_tlb_multi().  Is
> > that right?  It might be good to include some of that background in the
> > changelog to set the context.
>
> I’ll try to improve the change-logs a bit. There is no inherent reason for
> PV TLB-flushers not to implement their own flush_tlb_multi(). It is left
> for future work, and here are some reasons:
>
> 1. Hyper-V/Xen TLB-flushing code is not very simple
> 2. I don’t have a proper setup
> 3. I am lazy
>

In the long run, I think that we're going to want a way for one CPU to
do a remote flush and then, with appropriate locking, update the
tlb_gen fields for the remote CPU.  Getting this right may be a bit
nontrivial.

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190613064813.8102-1-namit@vmware.com>
2019-06-13  6:48 ` [PATCH 4/9] x86/mm/tlb: Flush remote and local TLBs concurrently Nadav Amit
2019-06-25 21:29   ` Dave Hansen
2019-06-26  2:35     ` Nadav Amit
2019-06-26  3:00       ` Dave Hansen
2019-06-26  3:32         ` Nadav Amit
2019-06-26  3:36   ` Andy Lutomirski
2019-06-26  3:48     ` Nadav Amit
2019-06-26  3:51       ` Andy Lutomirski
2019-06-13  6:48 ` [PATCH 6/9] KVM: x86: Provide paravirtualized flush_tlb_multi() Nadav Amit
2019-06-25 21:40   ` Dave Hansen
2019-06-26  2:39     ` Nadav Amit
2019-06-26  3:35       ` Andy Lutomirski [this message]
2019-06-26  3:41         ` Nadav Amit
2019-06-26  3:56           ` Andy Lutomirski
2019-06-26  6:30             ` Nadav Amit
2019-06-26 16:37               ` Andy Lutomirski
2019-06-26 17:41                 ` Vitaly Kuznetsov
2019-06-26 18:21                   ` Andy Lutomirski

Reply instructions:

You may reply publically 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='CALCETrWcUWw8ep-n6RaOeojnL924xOM7g7eb9g=3DRwOHQAgnA@mail.gmail.com' \
    --to=luto@kernel.org \
    --cc=bp@alien8.de \
    --cc=dave.hansen@intel.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=namit@vmware.com \
    --cc=pbonzini@redhat.com \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    /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

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org kvm@archiver.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/ public-inbox