Re: [PATCH 1/1] X86/Hyper-V:: Fix the circular dependency in IPI enlightenment.

Vitaly Kuznetsov
2018-07-04T09:13:52Z

kys@linuxonhyperv.com writes:

> From: "K. Y. Srinivasan" <kys@microsoft.com>
>
> The IPI hypercalls depend on being able to map the Linux notion of CPU ID
> to the hypervisor's notion of the CPU ID. The array hv_vp_index[] provides
> this mapping. Code for populating this array depends on the IPI functionality.
> Break this circular dependency.
>
> Fixes: 68bb7bfb7985 ("X86/Hyper-V: Enable IPI enlightenments")
>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> Tested-by: Michael Kelley <mikelley@microsoft.com>
> ---
> arch/x86/hyperv/hv_apic.c | 5 +++++
> arch/x86/hyperv/hv_init.c | 5 ++++-
> arch/x86/include/asm/mshyperv.h | 2 ++
> 3 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index f68855499391..63d7c196739f 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -114,6 +114,8 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector)
> ipi_arg->vp_set.format = HV_GENERIC_SET_SPARSE_4K;
> nr_bank = cpumask_to_vpset(&(ipi_arg->vp_set), mask);
> }
> + if (nr_bank == -1)
> + goto ipi_mask_ex_done;
> if (!nr_bank)
> ipi_arg->vp_set.format = HV_GENERIC_SET_ALL;
>
> @@ -158,6 +160,9 @@ static bool __send_ipi_mask(const struct cpumask *mask, int vector)
>
> for_each_cpu(cur_cpu, mask) {
> vcpu = hv_cpu_number_to_vp_number(cur_cpu);
> + if (vcpu == -1)
> + goto ipi_mask_done;
> +

Nit: hv_vp_index is u32 *, it would make sense to use U32_MAX instead of
'-1' everywhere in this patch.

> /*
> * This particular version of the IPI hypercall can
> * only target upto 64 CPUs.
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 4c431e1c1eff..04159893702e 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -265,7 +265,7 @@ void __init hyperv_init(void)
> {
> u64 guest_id, required_msrs;
> union hv_x64_msr_hypercall_contents hypercall_msr;
> - int cpuhp;
> + int cpuhp, i;
>
> if (x86_hyper_type != X86_HYPER_MS_HYPERV)
> return;
> @@ -293,6 +293,9 @@ void __init hyperv_init(void)
> if (!hv_vp_index)
> return;
>
> + for (i = 0; i < num_possible_cpus(); i++)
> + hv_vp_index[i] = -1;
> +
> hv_vp_assist_page = kcalloc(num_possible_cpus(),
> sizeof(*hv_vp_assist_page), GFP_KERNEL);
> if (!hv_vp_assist_page) {
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 3cd14311edfa..dee3f7347253 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -281,6 +281,8 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
> */
> for_each_cpu(cpu, cpus) {
> vcpu = hv_cpu_number_to_vp_number(cpu);
> + if (vcpu == -1)
> + return -1;
> vcpu_bank = vcpu / 64;
> vcpu_offset = vcpu % 64;
> __set_bit(vcpu_offset, (unsigned long *)

--
Vitaly