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    Subject[tip:x86/urgent] x86/hyper-v: Fix the circular dependency in IPI enlightenment
    Commit-ID:  5e6f19db2deca9e7eaa378447c77616b35693399
    Gitweb: https://git.kernel.org/tip/5e6f19db2deca9e7eaa378447c77616b35693399
    Author: K. Y. Srinivasan <kys@microsoft.com>
    AuthorDate: Tue, 3 Jul 2018 16:01:55 -0700
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Wed, 4 Jul 2018 10:50:03 +0200

    x86/hyper-v: Fix the circular dependency in IPI enlightenment

    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.

    Tested-by: Michael Kelley <mikelley@microsoft.com>
    Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
    Acked-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Michael.H.Kelley@microsoft.com
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: apw@canonical.com
    Cc: devel@linuxdriverproject.org
    Cc: gregkh@linuxfoundation.org
    Cc: jasowang@redhat.com
    Cc: olaf@aepfle.de
    Cc: sthemmin@microsoft.com
    Cc: vkuznets@redhat.com
    Fixes: 68bb7bfb7985 ("X86/Hyper-V: Enable IPI enlightenments")
    Link: http://lkml.kernel.org/r/20180703230155.15160-1-kys@linuxonhyperv.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    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;
    +
    /*
    * 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 *)
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