Messages in this thread | | | Date | Fri, 10 Mar 2023 16:13:54 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC][PATCH 5/5] x86/kvm: Simplify static call handling |
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On Fri, 10 Mar 2023 13:07:27 -0800 Sean Christopherson <seanjc@google.com> wrote:
> "KVM: x86:" please, "x86/kvm" is for guest-side changes. > > On Fri, Mar 10, 2023, Josh Poimboeuf wrote: > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index 1dfba499d3e5..612531e1c478 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -1789,8 +1789,6 @@ extern struct kvm_x86_ops kvm_x86_ops; > > > > #define KVM_X86_OP(func) \ > > DECLARE_STATIC_CALL(kvm_x86_##func, *(((struct kvm_x86_ops *)0)->func)); > > -#define KVM_X86_OP_OPTIONAL KVM_X86_OP > > -#define KVM_X86_OP_OPTIONAL_RET0 KVM_X86_OP > > #include <asm/kvm-x86-ops.h> > > > > int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops); > > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > > index 6accb46295a3..5f7f860c5f17 100644 > > --- a/arch/x86/kvm/pmu.c > > +++ b/arch/x86/kvm/pmu.c > > @@ -77,20 +77,15 @@ static struct kvm_pmu_ops kvm_pmu_ops __read_mostly; > > #define KVM_X86_PMU_OP(func) \ > > DEFINE_STATIC_CALL_NULL(kvm_x86_pmu_##func, \ > > *(((struct kvm_pmu_ops *)0)->func)); > > -#define KVM_X86_PMU_OP_OPTIONAL KVM_X86_PMU_OP > > #include <asm/kvm-x86-pmu-ops.h> > > > > void kvm_pmu_ops_update(const struct kvm_pmu_ops *pmu_ops) > > { > > memcpy(&kvm_pmu_ops, pmu_ops, sizeof(kvm_pmu_ops)); > > > > -#define __KVM_X86_PMU_OP(func) \ > > - static_call_update(kvm_x86_pmu_##func, kvm_pmu_ops.func); > > #define KVM_X86_PMU_OP(func) \ > > - WARN_ON(!kvm_pmu_ops.func); __KVM_X86_PMU_OP(func) > > I would much prefer to keep KVM mostly as-is, specifically so that we don't lose > this WARN_ON() that guards against a vendor module neglecting to implement a > mandatory callback. This effectively gives KVM "full" protection against consuming > an unexpectedly-NULL function pointer.
As in my reply to patch 0/5, I suggested that static_call_update(NULL) would trigger a WARN_ON() always. Then this could be cleaned up and still get that warning.
-- Steve
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