linux-kernel - [PATCH 0/5] KVM: RISC-V: VCPU reset fixes

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Message-ID: <20250403112522.1566629-3-rkrcmar@ventanamicro.com>
Date: Thu,  3 Apr 2025 13:25:19 +0200
From: Radim Krčmář <rkrcmar@...tanamicro.com>
To: kvm-riscv@...ts.infradead.org
Cc: kvm@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Anup Patel <anup@...infault.org>,
	Atish Patra <atishp@...shpatra.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alex@...ti.fr>,
	Andrew Jones <ajones@...tanamicro.com>,
	Mayuresh Chitale <mchitale@...tanamicro.com>
Subject: [PATCH 0/5] KVM: RISC-V: VCPU reset fixes

Hello,

this series started with a simple fix [5/5], which sadly didn't fix
enough without [4/5].  [1-3/5] are refactors to make the reset a bit
easier to follow.  ([1-3,5/5] are applicable without [4/5].)

[4/5] changes the userspace ABI and I'd like to gather your opinions on
how the ABI is supposed to work.

As another proposal, what do you think about an IOCTL that allows
userspace to invoke any KVM SBI ecall?
Userspace could call the KVM HSM implementation to reset and start a
VCPU, but I think that kvm_mp_state is an SBI HSM interface, so we have
an obscure IOCTL for it already.
I was also thinking about using KVM_MP_STATE_UNINITIALIZED to
distinguish that KVM should reset the state when becoming runnable.

I recommend to start with the following hunk in [4/5], as it's the only
significant part of this series:

  @@ -520,6 +525,10 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,

   	switch (mp_state->mp_state) {
   	case KVM_MP_STATE_RUNNABLE:
  +		if (riscv_vcpu_supports_sbi_ext(vcpu, KVM_RISCV_SBI_EXT_HSM) &&
  +				vcpu->arch.ran_atleast_once &&
  +				kvm_riscv_vcpu_stopped(vcpu))
  +			kvm_riscv_vcpu_sbi_request_reset_from_userspace(vcpu);

Thanks.

Radim Krčmář (5):
  KVM: RISC-V: refactor vector state reset
  KVM: RISC-V: refactor sbi reset request
  KVM: RISC-V: remove unnecessary SBI reset state
  KVM: RISC-V: reset VCPU state when becoming runnable
  KVM: RISC-V: reset smstateen CSRs

 arch/riscv/include/asm/kvm_aia.h         |  3 --
 arch/riscv/include/asm/kvm_host.h        | 13 +++--
 arch/riscv/include/asm/kvm_vcpu_sbi.h    |  5 ++
 arch/riscv/include/asm/kvm_vcpu_vector.h |  6 +--
 arch/riscv/kvm/aia_device.c              |  4 +-
 arch/riscv/kvm/vcpu.c                    | 69 +++++++++++++++---------
 arch/riscv/kvm/vcpu_sbi.c                | 28 ++++++++++
 arch/riscv/kvm/vcpu_sbi_hsm.c            | 13 +----
 arch/riscv/kvm/vcpu_sbi_system.c         | 10 +---
 arch/riscv/kvm/vcpu_vector.c             | 13 ++---
 10 files changed, 97 insertions(+), 67 deletions(-)

-- 
2.48.1