Received-SPF: pass (google.com: domain of linux-kernel+bounces-164642-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Reply-To: Sean Christopherson <seanjc@google.com>
Date: Tue, 30 Apr 2024 12:31:53 -0700
Precedence: bulk
Mime-Version: 1.0
Message-ID: <20240430193157.419425-1-seanjc@google.com>
Subject: [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()
From: Sean Christopherson <seanjc@google.com>
To: Marc Zyngier <maz@kernel.org>, Oliver Upton <oliver.upton@linux.dev>, 
	Tianrui Zhao <zhaotianrui@loongson.cn>, Bibo Mao <maobibo@loongson.cn>, 
	Huacai Chen <chenhuacai@kernel.org>, Michael Ellerman <mpe@ellerman.id.au>, 
	Anup Patel <anup@brainfault.org>, Paul Walmsley <paul.walmsley@sifive.com>, 
	Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, 
	Christian Borntraeger <borntraeger@linux.ibm.com>, Janosch Frank <frankja@linux.ibm.com>, 
	Claudio Imbrenda <imbrenda@linux.ibm.com>, Sean Christopherson <seanjc@google.com>, 
	Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, 
	kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, 
	linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, 
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"

Drop kvm_arch_sched_in() and instead pass a @sched_in boolean to
kvm_arch_vcpu_load().

While fiddling with an idea for optimizing state management on AMD CPUs,
I wanted to skip re-saving certain host state when a vCPU is scheduled back
in, as the state (theoretically) shouldn't change for the task while it's
scheduled out.  Actually doing that was annoying and unnecessarily brittle
due to having a separate API for the kvm_sched_in() case (the state save
needed to be in kvm_arch_vcpu_load() for the common path).

E.g. I could have set a "temporary"-ish flag somewhere in kvm_vcpu, but (a)
that's gross and (b) it would rely on the arbitrary ordering between
sched_in() and vcpu_load() staying the same.

The only real downside I see is that arm64 and riscv end up having to pass
"false" for their direct usage of kvm_arch_vcpu_load(), and passing boolean
literals isn't ideal.  But that can be solved by adding an inner helper that
omits the @sched_in param (I almost added a patch to do that, but I couldn't
convince myself it was necessary).

The other motivation for this is to avoid yet another arch hook, and more
arbitrary ordering, if there's a future need to hook kvm_sched_out() (we've
come close on the x86 side several times).

Sean Christopherson (4):
  KVM: Plumb in a @sched_in flag to kvm_arch_vcpu_load()
  KVM: VMX: Move PLE grow/shrink helpers above vmx_vcpu_load()
  KVM: x86: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()
  KVM: Delete the now unused kvm_arch_sched_in()

 arch/arm64/include/asm/kvm_host.h     |  1 -
 arch/arm64/kvm/arm.c                  |  2 +-
 arch/arm64/kvm/emulate-nested.c       |  4 +-
 arch/arm64/kvm/reset.c                |  2 +-
 arch/loongarch/include/asm/kvm_host.h |  1 -
 arch/loongarch/kvm/vcpu.c             |  2 +-
 arch/mips/include/asm/kvm_host.h      |  1 -
 arch/mips/kvm/mmu.c                   |  2 +-
 arch/powerpc/include/asm/kvm_host.h   |  1 -
 arch/powerpc/kvm/powerpc.c            |  2 +-
 arch/riscv/include/asm/kvm_host.h     |  1 -
 arch/riscv/kvm/vcpu.c                 |  4 +-
 arch/s390/include/asm/kvm_host.h      |  1 -
 arch/s390/kvm/kvm-s390.c              |  2 +-
 arch/x86/include/asm/kvm-x86-ops.h    |  1 -
 arch/x86/include/asm/kvm_host.h       |  4 +-
 arch/x86/kvm/pmu.c                    |  6 +--
 arch/x86/kvm/svm/svm.c                | 13 ++---
 arch/x86/kvm/vmx/main.c               |  2 -
 arch/x86/kvm/vmx/vmx.c                | 75 +++++++++++++--------------
 arch/x86/kvm/vmx/x86_ops.h            |  3 +-
 arch/x86/kvm/x86.c                    | 26 +++++-----
 include/linux/kvm_host.h              |  4 +-
 virt/kvm/kvm_main.c                   |  5 +-
 24 files changed, 70 insertions(+), 95 deletions(-)


base-commit: a96cb3bf390eebfead5fc7a2092f8452a7997d1b
-- 
2.45.0.rc0.197.gbae5840b3b-goog