Re: [PATCH] RISC-V: KVM: Fix IPI delivery for out-of-order vcpu_id

[Troy Mitchell]

On Thu Sep 17, 2026 at 8:20 PM +08, Xiaofeng Yuan wrote:
> The SBI IPI handler walks vCPUs with kvm_for_each_vcpu(), which
> iterates by vcpu_idx (creation order) rather than vcpu_id order.
> Since vcpu_id can be assigned out of order by userspace, a vCPU whose
> hart_bit falls outside the XLEN-bit hart_mask range may be reached
> before vCPUs the mask actually targets. In that case the handler jumps
> to "done" and stops sending IPIs, leaving valid target vCPUs without
> an interrupt.
>
> Replace the early "goto done" with "continue" so vCPUs outside the
> hart_mask range are skipped without aborting the loop.
>
> Reproduced with a minimal userspace VMM driving KVM inside a QEMU
> (RISC-V virt) guest: three vCPUs are created with ids 100, 0, 1 (in
> creation order) and sbi_send_ipi(hart_mask=bit0, hbase=0) is called
> from vcpu_id 1. Before this change the IPI is dropped and the ecall
> returns SBI_ERR_INVALID_PARAM; with this change the IPI is delivered
> and the ecall returns SBI_SUCCESS.
>
> Fixes: 0611f78f83c9 ("riscv: KVM: Fix SBI IPI error generation")
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> Signed-off-by: Xiaofeng Yuan <yuanxiaofeng@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Troy Mitchell <troy.mitchell@xxxxxxxxxxxxxxxxxx>

-- 
Troy Mitchell

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