Re: [PATCH] RISC-V: KVM: Use raw_spinlock for VMID update critical section

Sebastian Andrzej Siewior <[email protected]> Fri, 17 Jul 2026 08:51:37 +0200

Newsgroups	org.infradead.lists.kvm-riscv,dev.linux.lists.linux-rt-devel,org.infradead.lists.linux-riscv,org.kernel.vger.kvm,org.kernel.vger.linux-kernel
Message-ID	<[email protected]>

On 2026-07-16 14:40:11 [+0800], [email protected] wrote:
> From: "Yuhang.chen" <[email protected]>
> 
> The VMID update critical section performs an IPI broadcast via
> on_each_cpu_mask() on VMID version rollover, which must not be preempted
> under PREEMPT_RT.

Here you state _why_ it must not be preempted. What would be the worst
that could happen.

>                   Convert vmid_lock to raw_spinlock_t and use plain
That part starting with "Convert" belongs into into a new line.

> raw_spin_lock()/raw_spin_unlock() (interrupts stay enabled, since
> on_each_cpu_mask() requires it).
> 
> Assisted-by: YuanSheng:deepseek-v4-pro
> Co-developed-by: Quan Zhou <[email protected]>
> Signed-off-by: Quan Zhou <[email protected]>
> Signed-off-by: Yuhang.chen <[email protected]>

Sebastian

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