On 2024/8/28 09:07, maobibo wrote:

Zenghui,

On 2024/8/27 上午1:00, Zenghui Yu wrote:

quoted

On 2024/8/26 13:47, Dandan Zhang wrote:

quoted

+KVM Hypercalls Documentation
+============================
+
+The template for each hypercall is as follows:
+
+1. Hypercall name
+2. Purpose
+
+1. KVM_HCALL_FUNC_PV_IPI

Is it still a work-in-progress thing? I don't see it in mainline.

It should be KVM_HCALL_FUNC_IPI here.

Good! So that I can probably read further. :-)

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quoted

+------------------------
+
+:Purpose: Send IPIs to multiple vCPUs.
+
+- a0: KVM_HCALL_FUNC_PV_IPI
+- a1: Lower part of the bitmap for destination physical CPUIDs
+- a2: Higher part of the bitmap for destination physical CPUIDs
+- a3: The lowest physical CPUID in the bitmap

- Is it a feature that implements IPI broadcast with a PV method?
- Don't you need to *at least* specify which IPI to send by issuing this
  hypercall?

Good question. It should be documented here. PV IPI on LoongArch
includes both PV IPI multicast sending and PV IPI receiving, and SWI is

Oh yup, I intended to say "multicast". Thanks for the explanation.

used for PV IPI inject since there is no VM-exits accessing SWI registers.

quoted

But again, as I said I know nothing about loongarch.  I might have
missed some obvious points.

quoted

+
+The hypercall lets a guest send multiple IPIs (Inter-Process
Interrupts) with
+at most 128 destinations per hypercall.The destinations are
represented in a

                                           ^
Add a blank space.

quoted

+bitmap contained in the first two input registers (a1 and a2).
+
+Bit 0 of a1 corresponds to the physical CPUID in the third input
register (a3)
+and bit 1 corresponds to the physical CPUID in a3+1 (a4), and so on.

This looks really confusing.  "Bit 63 of a1 corresponds to the physical
CPUID in a3+63 (a66)"?

The description is problematic, thanks for pointing it out.
It should be value of register a3 plus 1, rather than a4, how about
*"the physical CPUID in a3 + 1"*  here?

Better than the original version, I think.

Thanks,
Zenghui