linux-kernel - Re: [GIT PULL (sort of)] KVM: x86: Static call changes for 6.11

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Message-ID: <0f60918d-bc46-4332-ad28-c155a1990e3d@redhat.com>
Date: Tue, 16 Jul 2024 16:16:30 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL (sort of)] KVM: x86: Static call changes for 6.11

On 7/13/24 01:56, Sean Christopherson wrote:
> Here's a massage pull request for the static_call() changes, just in case you
> want to go this route instead of applying patches directly after merging
> everything else for 6.11 (it was easy to generate this).  If you want to go the
> patches route, I'll post 'em next week.
> 
> The following changes since commit c1c8a908a5f4c372f8a8dca0501b56ffc8d260fe:
> 
>    Merge branch 'vmx' (2024-06-28 22:22:53 +0000)
> 
> are available in the Git repository at:
> 
>    https://github.com/kvm-x86/linux.git  tags/kvm-x86-static_calls-6.11
> 
> for you to fetch changes up to b528de209c858f61953023b405a4abbf9a9933da:
> 
>    KVM: x86/pmu: Add kvm_pmu_call() to simplify static calls of kvm_pmu_ops (2024-06-28 15:23:49 -0700)

Thanks, indeed there was no straggler static_call() after applying
this.  However, there might be a problem: static_call_cond() is equal
to static_call() only if CONFIG_HAVE_STATIC_CALL_INLINE, and arch/x86
has this:

         select HAVE_STATIC_CALL_INLINE          if HAVE_OBJTOOL
         select HAVE_OBJTOOL                     if X86_64

And indeed if I apply

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 80e5afde69f4..d20159d4a37a 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -21,6 +21,8 @@ config KVM
  	tristate "Kernel-based Virtual Machine (KVM) support"
  	depends on HIGH_RES_TIMERS
  	depends on X86_LOCAL_APIC
+	# KVM relies on static_call_cond() being the same as static_call()
+	depends on HAVE_STATIC_CALL_INLINE
  	select KVM_COMMON
  	select KVM_GENERIC_MMU_NOTIFIER
  	select HAVE_KVM_IRQCHIP

KVM disappears from 32-bit kernels. :)  So I haven't checked but I
suspect this breaks 32-bit?

Paolo