[PATCH 0/2] KVM: x86: Fix more KVM_X86 Kconfig bugs

[PATCH 0/2] KVM: x86: Fix more KVM_X86 Kconfig bugs

[Sean Christopherson]

Fix two more bugs in the KVM_X86 Kconfig.  The fix from Arnd resolves a
build failure, but practically speaking is a non-issue because the failure
only affects 32-bit !SMP builds that effectively disable the local APIC.

The second fix is far more urgent.  It resolves a bug where KVM's Kconfig
doesn't correctly define KVM_X86, and will build kvm.ko as a module when
KVM=y if neither KVM_INTEL nor KVM_AMD is 'y', e.g. if KVM=y, KVM_INTEL,=m,
and KVM_AMD=m.  I don't know if any distros use that combo, but it broke
our production kernel, so it's certainly possible that it broke other
setups too.

Arnd's fix was already posted, but I bundled it here to avoid a trivial
conflict and to ensure it doesn't get left behind.

Arnd Bergmann (1):
  KVM: x86: add back X86_LOCAL_APIC dependency

Sean Christopherson (1):
  KVM: x86: Break CONFIG_KVM_X86's direct dependency on KVM_INTEL ||
    KVM_AMD

 arch/x86/kvm/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


base-commit: adc218676eef25575469234709c2d87185ca223a
-- 
2.47.0.338.g60cca15819-goog

[PATCH 1/2] KVM: x86: add back X86_LOCAL_APIC dependency

[Sean Christopherson]

From: Arnd Bergmann <arnd@arndb.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")
Cc: stable@vger.kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410060426.e9Xsnkvi-lkp@intel.com/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sean Christopherson <seanjc@google.com>
[sean: add Cc to stable, tweak shortlog scope]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index f09f13c01c6b..887df30297f3 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 HAVE_KVM_IRQCHIP
@@ -49,6 +48,7 @@ config KVM_X86
 
 config KVM
 	tristate "Kernel-based Virtual Machine (KVM) support"
+	depends on X86_LOCAL_APIC
 	help
 	  Support hosting fully virtualized guest machines using hardware
 	  virtualization extensions.  You will need a fairly recent
-- 
2.47.0.338.g60cca15819-goog

[PATCH 2/2] KVM: x86: Break CONFIG_KVM_X86's direct dependency on KVM_INTEL || KVM_AMD

[Sean Christopherson]

Rework CONFIG_KVM_X86's dependency to only check if KVM_INTEL or KVM_AMD
is selected, i.e. not 'n'.  Having KVM_X86 depend directly on the vendor
modules results in KVM_X86 being set to 'm' if at least one of KVM_INTEL
or KVM_AMD is enabled, but neither is 'y', regardless of the value of KVM
itself.

The documentation for def_tristate doesn't explicitly state that this is
the intended behavior, but it does clearly state that the "if" section is
parsed as a dependency, i.e. the behavior is consistent with how tristate
dependencies are handled in general.

  Optionally dependencies for this default value can be added with "if".

Fixes: ea4290d77bda ("KVM: x86: leave kvm.ko out of the build if no vendor module is requested")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 887df30297f3..b91ec2e9c916 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -18,7 +18,7 @@ menuconfig VIRTUALIZATION
 if VIRTUALIZATION
 
 config KVM_X86
-	def_tristate KVM if KVM_INTEL || KVM_AMD
+	def_tristate KVM if (KVM_INTEL != n || KVM_AMD != n)
 	select KVM_COMMON
 	select KVM_GENERIC_MMU_NOTIFIER
 	select HAVE_KVM_IRQCHIP
-- 
2.47.0.338.g60cca15819-goog

Re: [PATCH 0/2] KVM: x86: Fix more KVM_X86 Kconfig bugs

[Paolo Bonzini]

Queued, thanks.

Paolo