Re: [PATCH 0/2] Few timer and AIA fixes for KVM RISC-V

[Atish Patra <atish.patra@linux.dev>]

On 7/4/25 8:38 AM, Anup Patel wrote:
> The RISC-V Privileged specificaiton says the following: "WFI is also
> required to resume execution for locally enabled interrupts pending
> at any privilege level, regardless of the global interrupt enable at
> each privilege level."
>
> Based on the above, if there is pending VS-timer interrupt when the
> host (aka HS-mode) executes WFI then such a WFI will simply become NOP
> and not do anything. This result in QEMU RISC-V consuming a lot of CPU
> time on the x86 machine where it is running. The PATCH1 solves this
> issue by adding appropriate cleanup in KVM RISC-V timer virtualization.
>
> As a result PATCH1, race conditions in updating HGEI[E|P] CSRs when a
> VCPU is moved from one host CPU to another are being observed on QEMU
> so the PATCH2 tries to minimize the chances of these race conditions.
>
> Anup Patel (2):
>    RISC-V: KVM: Disable vstimecmp before exiting to user-space
>    RISC-V: KVM: Move HGEI[E|P] CSR access to IMSIC virtualization
>
>   arch/riscv/include/asm/kvm_aia.h |  4 ++-
>   arch/riscv/kvm/aia.c             | 51 +++++---------------------------
>   arch/riscv/kvm/aia_imsic.c       | 45 ++++++++++++++++++++++++++++
>   arch/riscv/kvm/vcpu.c            |  2 --
>   arch/riscv/kvm/vcpu_timer.c      | 16 ++++++++++
>   5 files changed, 71 insertions(+), 47 deletions(-)
>
For the entire series :

Tested-by: Atish Patra <atishp@rivosinc.com>

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