RE: [PATCH v5 09/10] x86/hyper-v: support extended CPU ranges for TLB flush hypercalls

[Jork Loeser]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> Sent: Tuesday, May 30, 2017 04:34
> To: x86@xxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang
> Zhang <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Ingo
> Molnar <mingo@xxxxxxxxxx>; H. Peter Anvin <hpa@xxxxxxxxx>; Steven
> Rostedt <rostedt@xxxxxxxxxxx>; Jork Loeser <Jork.Loeser@xxxxxxxxxxxxx>;
> Simon Xiao <sixiao@xxxxxxxxxxxxx>; Andy Lutomirski <luto@xxxxxxxxxx>; Andy
> Shevchenko <andy.shevchenko@xxxxxxxxx>
> Subject: [PATCH v5 09/10] x86/hyper-v: support extended CPU ranges for TLB
> flush hypercalls
> 
> Hyper-V hosts may support more than 64 vCPUs, we need to use
> HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX/LIST_EX hypercalls in this case.


> +static inline int cpumask_to_vp_set(struct hv_flush_pcpu_ex *flush,
> +				    const struct cpumask *cpus)
> +{
> +	int cpu, vcpu, vcpu_bank, vcpu_offset, cur_bank, nr_bank = 0;
> +	bool has_cpus;
> +
> +	/*
> +	 * We can't be sure that translated vCPU numbers will always be
> +	 * in ascending order, so iterate over all possible banks and
> +	 * check all vCPUs in it instead.
> +	 */
> +	for (cur_bank = 0; cur_bank < ms_hyperv.max_vp_index/64;
> cur_bank++) {
> +		has_cpus = false;
> +		for_each_cpu(cpu, cpus) {
> +			vcpu = hv_cpu_number_to_vp_number(cpu);
> +			vcpu_bank = vcpu / 64;
> +			vcpu_offset = vcpu % 64;
> +
> +			if (vcpu_bank != cur_bank)
> +				continue;
> +			__set_bit(vcpu_offset, (unsigned long *)
> +				  &flush->hv_vp_set.bank_contents[nr_bank]);
> +			if (!has_cpus) {
> +				__set_bit(vcpu_bank, (unsigned long *)
> +					  &flush->hv_vp_set.valid_bank_mask);
> +				has_cpus = true;
> +			}
> +		}
> +		if (has_cpus)
> +			nr_bank++;
> +	}
> +
> +	return nr_bank;
> +}

Note that the HV_VP_SET may contain empty banks. As such, consider enabling all (5) bits in the valid_bank_mask, and a single for_each(cpu, cpus) pass - setting the bits as per hv_cpu_number_to_vp_number(cpu).

Regards,
Jork