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    SubjectRe: [PATCH v5 05/30] KVM: Provide more information in kernel log if hardware enabling fails
    On Thu, Sep 22, 2022, isaku.yamahata@intel.com wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > Provide the name of the calling function to hardware_enable_nolock() and
    > include it in the error message to provide additional information on
    > exactly what path failed.

    Changelog doesn't match the code.

    > Opportunistically bump the pr_info() to pr_warn(), failure to enable
    > virtualization support is warn-worthy as _something_ is wrong with the
    > system.
    >
    > Suggested-by: Chao Gao <chao.gao@intel.com>
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > ---
    > virt/kvm/kvm_main.c | 3 ++-
    > 1 file changed, 2 insertions(+), 1 deletion(-)
    >
    > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    > index 4243a9541543..4f19c47aab1c 100644
    > --- a/virt/kvm/kvm_main.c
    > +++ b/virt/kvm/kvm_main.c
    > @@ -5006,7 +5006,8 @@ static void hardware_enable_nolock(void *junk)
    > if (r) {
    > cpumask_clear_cpu(cpu, cpus_hardware_enabled);
    > atomic_inc(&hardware_enable_failed);
    > - pr_info("kvm: enabling virtualization on CPU%d failed\n", cpu);
    > + pr_warn("kvm: enabling virtualization on CPU%d failed during %pSb\n",
    > + cpu, __builtin_return_address(0));

    I vote to drop this patch. Trying to capture the caller is just a poor man's
    version of WARN, and at the end of this series KVM should be at a point where KVM
    can WARN when hardware enabling indicates a potentially fatal issue.

    Specifically, kvm_arch_add_vm() shouldn't WARN since x86 can fail due a misbehaving
    userspace. kvm_arch_online_cpu() on the other hand can and should WARN since
    failure in that case means hardware enabling succeeded on other CPUs, and in the x86
    case, that KVM is actively running VMs.

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