Re: [PATCH 4.19 042/190] KVM: x86: hyperv: keep track of mismatched VP indexes

Pavel Machek
2019-09-15T16:55:26Z

On Fri 2019-09-13 14:04:57, Greg Kroah-Hartman wrote:
> [ Upstream commit 87ee613d076351950b74383215437f841ebbeb75 ]
>
> In most common cases VP index of a vcpu matches its vcpu index. Userspace is, however,
> free to set any mapping it wishes and we need to account for that when we need to find a
> vCPU with a particular VP index. To keep search algorithms optimal in both cases
> introduce 'num_mismatched_vp_indexes' counter showing how many vCPUs with mismatching VP
> index we have. In case the counter is zero we can assume vp_index == vcpu_idx.

I don't see why this is stable material.

> u64 hv_reenlightenment_control;
> u64 hv_tsc_emulation_control;
> u64 hv_tsc_emulation_status;
> +
> + /* How many vCPUs have VP index != vCPU index */
> + atomic_t num_mismatched_vp_indexes;
> };
>

It adds a write-only variable ...

Best regards,
Pavel

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