Re: [PATCH v3 00/15] KVM: Dynamically size memslot arrays

From: Christian Borntraeger <borntraeger@de.ibm.com>
To: "Sean Christopherson" <sean.j.christopherson@intel.com>,
	"James Hogan" <jhogan@kernel.org>,
	"Paul Mackerras" <paulus@ozlabs.org>,
	"Janosch Frank" <frankja@linux.ibm.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Marc Zyngier" <maz@kernel.org>
Cc: Wanpeng Li <wanpengli@tencent.com>,
	kvm@vger.kernel.org, David Hildenbrand <david@redhat.com>,
	Joerg Roedel <joro@8bytes.org>, Cornelia Huck <cohuck@redhat.com>,
	linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	kvmarm@lists.cs.columbia.edu, Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v3 00/15] KVM: Dynamically size memslot arrays
Date: Mon, 16 Dec 2019 09:25:24 +0100	[thread overview]
Message-ID: <ca928a38-4bc0-88cd-dc70-62aec8695c77@de.ibm.com> (raw)
In-Reply-To: <20191213200151.GF31552@linux.intel.com>

On 13.12.19 21:01, Sean Christopherson wrote:
> On Tue, Dec 03, 2019 at 02:14:33PM -0800, Sean Christopherson wrote:
>> On Thu, Oct 24, 2019 at 04:07:29PM -0700, Sean Christopherson wrote:
>>> The end goal of this series is to dynamically size the memslot array so
>>> that KVM allocates memory based on the number of memslots in use, as
>>> opposed to unconditionally allocating memory for the maximum number of
>>> memslots.  On x86, each memslot consumes 88 bytes, and so with 2 address
>>> spaces of 512 memslots, each VM consumes ~90k bytes for the memslots.
>>> E.g. given a VM that uses a total of 30 memslots, dynamic sizing reduces
>>> the memory footprint from 90k to ~2.6k bytes.
>>>
>>> The changes required to support dynamic sizing are relatively small,
>>> e.g. are essentially contained in patches 14/15 and 15/15.  Patches 1-13
>>> clean up the memslot code, which has gotten quite crusty, especially
>>> __kvm_set_memory_region().  The clean up is likely not strictly necessary
>>> to switch to dynamic sizing, but I didn't have a remotely reasonable
>>> level of confidence in the correctness of the dynamic sizing without first
>>> doing the clean up.
>>>
>>> Christoffer, I added your Tested-by to the patches that I was confident
>>> would be fully tested based on the desription of what you tested.  Let me
>>> know if you disagree with any of 'em.
>>>
>>> v3:
>>>   - Fix build errors on PPC and MIPS due to missed params during
>>>     refactoring [kbuild test robot].
>>>   - Rename the helpers for update_memslots() and add comments describing
>>>     the new algorithm and how it interacts with searching [Paolo].
>>>   - Remove the unnecessary and obnoxious warning regarding memslots being
>>>     a flexible array [Paolo].
>>>   - Fix typos in the changelog of patch 09/15 [Christoffer].
>>>   - Collect tags [Christoffer].
>>>
>>> v2:
>>>   - Split "Drop kvm_arch_create_memslot()" into three patches to move
>>>     minor functional changes to standalone patches [Janosch].
>>>   - Rebase to latest kvm/queue (f0574a1cea5b, "KVM: x86: fix ...")
>>>   - Collect an Acked-by and a Reviewed-by
>>
>> Paolo, do you want me to rebase this to the latest kvm/queue?
> 
> Ping.
> 
> Applies cleanly on the current kvm/queue and nothing caught fire in
> testing (though I only re-tested the series as a whole).

Do you have the latest version somewhere on a branch? The version on the
list no longer applies cleanly.  

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