linux-kernel - Re: [PATCH v3 0/2] RISC-V: KVM: VCPU reset fixes

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Message-ID: <1a7a81fd-cf15-4b54-a805-32d66ced4517@linux.dev>
Date: Thu, 22 May 2025 14:43:40 -0700
From: Atish Patra <atish.patra@...ux.dev>
To: Radim Krčmář <rkrcmar@...tanamicro.com>,
 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>
Subject: Re: [PATCH v3 0/2] RISC-V: KVM: VCPU reset fixes

On 5/15/25 7:37 AM, Radim KrÄmÃ¡Å wrote:
> Hello,
> 
> the design still requires a discussion.
> 
> [v3 1/2] removes most of the additional changes that the KVM capability
> was doing in v2.  [v3 2/2] is new and previews a general solution to the
> lack of userspace control over KVM SBI.
> 

I am still missing the motivation behind it. If the motivation is SBI 
HSM suspend, the PATCH2 doesn't achieve that as it forwards every call 
to the user space. Why do you want to control hsm start/stop from the 
user space ?


> A possible QEMU implementation for both capabilities can be seen in
> https://github.com/radimkrcmar/qemu/tree/reset_fixes_v3
> The next step would be to forward the HSM ecalls to QEMU.
> 
> v2: https://lore.kernel.org/kvm-riscv/20250508142842.1496099-2-rkrcmar@ventanamicro.com/
> v1: https://lore.kernel.org/kvm-riscv/20250403112522.1566629-3-rkrcmar@ventanamicro.com/
> 
> Radim Krčmář (2):
>    RISC-V: KVM: add KVM_CAP_RISCV_MP_STATE_RESET
>    RISC-V: KVM: add KVM_CAP_RISCV_USERSPACE_SBI
> 
>   Documentation/virt/kvm/api.rst        | 22 ++++++++++++++++++++++
>   arch/riscv/include/asm/kvm_host.h     |  6 ++++++
>   arch/riscv/include/asm/kvm_vcpu_sbi.h |  1 +
>   arch/riscv/kvm/vcpu.c                 | 27 ++++++++++++++-------------
>   arch/riscv/kvm/vcpu_sbi.c             | 27 +++++++++++++++++++++++++--
>   arch/riscv/kvm/vm.c                   | 18 ++++++++++++++++++
>   include/uapi/linux/kvm.h              |  2 ++
>   7 files changed, 88 insertions(+), 15 deletions(-)
>