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From: Marc Zyngier <maz@kernel.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH] KVM: move struct kvm_vcpu * array to the bottom of struct kvm
Date: Fri, 05 Nov 2021 18:37:48 +0000	[thread overview]
Message-ID: <87wnlm8n43.wl-maz@kernel.org> (raw)
In-Reply-To: <YYVElU6u22qxgQIz@google.com>

On Fri, 05 Nov 2021 14:49:57 +0000,
Sean Christopherson <seanjc@google.com> wrote:
> 
> +Juergen and Marc
> 
> On Fri, Nov 05, 2021, Nicholas Piggin wrote:
> > Increasing the max VCPUs on powerpc makes the kvm_arch member offset
> > great enough that some assembly breaks due to addressing constants
> > overflowing field widths.
> > 
> > Moving the vcpus array to the end of struct kvm prevents this from
> > happening. It has the side benefit that moving the large array out
> > from the middle of the structure should help keep other commonly
> > accessed fields in the same or adjacent cache lines.
> > 
> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> > ---
> > 
> > It would next be possible to now make this a dynamically sized array,
> > and make the KVM_MAX_VCPUS more dynamic
> 
> Marc has a mostly-baked series to use an xarray[1][2] that AFAICT
> would be well received.  That has my vote, assuming it can get into
> 5.16.  Marc or Juergen, are either of you actively working on that?

I've just revived it, as it needed some RISC-V changes. I'll post it
in a jiffy.

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2021-11-05 18:37 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-05  3:49 [PATCH] KVM: move struct kvm_vcpu * array to the bottom of struct kvm Nicholas Piggin
2021-11-05 14:49 ` Sean Christopherson
2021-11-05 18:37   ` Marc Zyngier [this message]
2021-11-06  0:29   ` Nicholas Piggin
2021-11-08 15:35     ` Sean Christopherson

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