linux-kernel - [PATCH] x86: kvm: add back X86_LOCAL

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Message-Id: <20241112065415.3974321-1-arnd@kernel.org>
Date: Tue, 12 Nov 2024 07:53:59 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org
Cc: Arnd Bergmann <arnd@...db.de>,
	kernel test robot <lkp@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Michael Roth <michael.roth@....com>,
	Isaku Yamahata <isaku.yamahata@...el.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86: kvm: add back X86_LOCAL_APIC dependency

From: Arnd Bergmann <arnd@...db.de>

Enabling KVM now causes a build failure on x86-32 if X86_LOCAL_APIC
is disabled:

arch/x86/kvm/svm/svm.c: In function 'svm_emergency_disable_virtualization_cpu':
arch/x86/kvm/svm/svm.c:597:9: error: 'kvm_rebooting' undeclared (first use in this function); did you mean 'kvm_irq_routing'?
  597 |         kvm_rebooting = true;
      |         ^~~~~~~~~~~~~
      |         kvm_irq_routing
arch/x86/kvm/svm/svm.c:597:9: note: each undeclared identifier is reported only once for each function it appears in
make[6]: *** [scripts/Makefile.build:221: arch/x86/kvm/svm/svm.o] Error 1
In file included from include/linux/rculist.h:11,
                 from include/linux/hashtable.h:14,
                 from arch/x86/kvm/svm/avic.c:18:
arch/x86/kvm/svm/avic.c: In function 'avic_pi_update_irte':
arch/x86/kvm/svm/avic.c:909:38: error: 'struct kvm' has no member named 'irq_routing'
  909 |         irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
      |                                      ^~
include/linux/rcupdate.h:538:17: note: in definition of macro '__rcu_dereference_check'
  538 |         typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \

Move the dependency to the same place as before.

Fixes: ea4290d77bda ("KVM: x86: leave kvm.ko out of the build if no vendor module is requested")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410060426.e9Xsnkvi-lkp@intel.com/
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Question: is there actually any point in keeping KVM support for 32-bit host
processors? From what I can tell, the only 32-bit CPUs that support this are
the rare Atom E6xx and Z5xx models and the even older Yonah/Sossaman "Core
Duo", everything else is presumably better off just running a 64-bit kernel
even for 32-bit guests?
---
 arch/x86/kvm/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 1ed1e4f5d51c..849a03f3ba95 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -19,7 +19,6 @@ if VIRTUALIZATION
 
 config KVM_X86
 	def_tristate KVM if KVM_INTEL || KVM_AMD
-	depends on X86_LOCAL_APIC
 	select KVM_COMMON
 	select KVM_GENERIC_MMU_NOTIFIER
 	select KVM_ELIDE_TLB_FLUSH_IF_YOUNG
@@ -93,6 +92,7 @@ config KVM_SW_PROTECTED_VM
 config KVM_INTEL
 	tristate "KVM for Intel (and compatible) processors support"
 	depends on KVM && IA32_FEAT_CTL
+	depends on X86_LOCAL_APIC
 	help
 	  Provides support for KVM on processors equipped with Intel's VT
 	  extensions, a.k.a. Virtual Machine Extensions (VMX).
@@ -130,6 +130,7 @@ config X86_SGX_KVM
 config KVM_AMD
 	tristate "KVM for AMD processors support"
 	depends on KVM && (CPU_SUP_AMD || CPU_SUP_HYGON)
+	depends on X86_LOCAL_APIC
 	help
 	  Provides support for KVM on AMD processors equipped with the AMD-V
 	  (SVM) extensions.
-- 
2.39.5