[PATCH 00/15] Move vcpu_load and vcpu_put calls to arch code

[Paolo Bonzini]

On 28/11/2017 21:55, David Hildenbrand wrote:
> On 25.11.2017 21:57, Christoffer Dall wrote:
>> Some architectures may decide to do different things during
>> kvm_arch_vcpu_load depending on the ioctl being executed.  For example,
>> arm64 is about to do significant work in vcpu load/put when running a
>> vcpu, but it's problematic to do this for any other vcpu ioctl than
>> KVM_RUN.
>>
>> Further, while it may be possible to call kvm_arch_vcpu_load() for a
>> number of non-KVM_RUN ioctls, it makes the KVM/ARM code more difficult
>> to reason about, especially after my optimization series, because a lot
>> of things can now happen, where we have to consider if we're really in
>> the process of running a vcpu or not.
>>
>> This series will first move the vcpu_load() and vcpu_put() calls in the
>> arch generic dispatch function into each case of the switch statement
>> and then, one-by-one, pushed the calls down into the architecture
>> specific code making the changes for each ioctl as required.
>>
>> Thanks,
>> -Christoffer
>>
>> Christoffer Dall (15):
>>   KVM: Prepare for moving vcpu_load/vcpu_put into arch specific code
>>   KVM: Factor out vcpu->pid adjustment for KVM_RUN
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_run
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_get_regs
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_set_regs
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_get_sregs
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_set_sregs
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_get_mpstate
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_set_mpstate
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_translate
>>   KVM: Move vcpu_load to arch-specific
>>     kvm_arch_vcpu_ioctl_set_guest_debug
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_get_fpu
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_set_fpu
>>   KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl
>>   KVM: arm/arm64: Avoid vcpu_load for other vcpu ioctls than KVM_RUN
>>
>>  arch/arm64/kvm/guest.c     |  17 +++++--
>>  arch/mips/kvm/mips.c       |  72 +++++++++++++++++++--------
>>  arch/powerpc/kvm/book3s.c  |  38 +++++++++++++-
>>  arch/powerpc/kvm/booke.c   |  65 +++++++++++++++++++-----
>>  arch/powerpc/kvm/powerpc.c |  24 ++++++---
>>  arch/s390/kvm/kvm-s390.c   | 119 +++++++++++++++++++++++++++++++++++++-------
>>  arch/x86/kvm/x86.c         | 121 ++++++++++++++++++++++++++++++++++++++-------
>>  include/linux/kvm_host.h   |   2 +
>>  virt/kvm/arm/arm.c         |  91 +++++++++++++++++++++++++---------
>>  virt/kvm/kvm_main.c        |  43 +++++++---------
>>  10 files changed, 463 insertions(+), 129 deletions(-)
>>
> 
> Looking at the amount of code we duplicate, I wonder if simple ifdefery
> (if possible) would be easier for the single known "special" case.
> 
> (most probably an unpopular opinion :) )

No, also because the duplicate code will go down sensibly in the next
version.

Paolo