[PATCH 0/5] KVM: Turn the vcpu array into an xarray

[Juergen Gross]

On 16.11.21 15:21, Paolo Bonzini wrote:
> On 11/16/21 15:13, Juergen Gross wrote:
>> On 05.11.21 20:20, Marc Zyngier wrote:
>>> The kvm structure is pretty large. A large portion of it is the vcpu
>>> array, which is 4kB on x86_64 and arm64 as they deal with 512 vcpu
>>> VMs. Of course, hardly anyone runs VMs this big, so this is often a
>>> net waste of memory and cache locality.
>>>
>>> A possible approach is to turn the fixed-size array into an xarray,
>>> which results in a net code deletion after a bit of cleanup.
>>>
>>> This series is on top of the current linux/master as it touches the
>>> RISC-V implementation. Only tested on arm64.
>>>
>>> Marc Zyngier (5):
>>>    KVM: Move wiping of the kvm->vcpus array to common code
>>>    KVM: mips: Use kvm_get_vcpu() instead of open-coded access
>>>    KVM: s390: Use kvm_get_vcpu() instead of open-coded access
>>>    KVM: x86: Use kvm_get_vcpu() instead of open-coded access
>>>    KVM: Convert the kvm->vcpus array to a xarray
>>>
>>>   arch/arm64/kvm/arm.c           | 10 +---------
>>>   arch/mips/kvm/loongson_ipi.c   |  4 ++--
>>>   arch/mips/kvm/mips.c           | 23 ++---------------------
>>>   arch/powerpc/kvm/powerpc.c     | 10 +---------
>>>   arch/riscv/kvm/vm.c            | 10 +---------
>>>   arch/s390/kvm/kvm-s390.c       | 26 ++++++--------------------
>>>   arch/x86/kvm/vmx/posted_intr.c |  2 +-
>>>   arch/x86/kvm/x86.c             |  9 +--------
>>>   include/linux/kvm_host.h       |  7 ++++---
>>>   virt/kvm/kvm_main.c            | 33 ++++++++++++++++++++++++++-------
>>>   10 files changed, 45 insertions(+), 89 deletions(-)
>>>
>>
>> For x86 you can add my:
>>
>> Tested-by: Juergen Gross <jgross at suse.com>
> 
> Heh, unfortunately x86 is the only one that needs a change in patch 4. 
> I'll Cc you on my version.

I guess the changes in kvm_main.c are more important for my series. :-)

I've replaced patch 4 with your variant and everything is still working.
Not sure how relevant that is, though.


Juergen

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