x86: Restrict KVM-induced symbol exports to KVM modules where obvious/possible

Extend KVM's export macro framework to provide EXPORT_SYMBOL_FOR_KVM(),
and use the helper macro to export symbols for KVM throughout x86 if and
only if KVM will build one or more modules, and only for those modules.

To avoid unnecessary exports when CONFIG_KVM=m but kvm.ko will not be
built (because no vendor modules are selected), let arch code #define
EXPORT_SYMBOL_FOR_KVM to suppress/override the exports.

Note, the set of symbols to restrict to KVM was generated by manual search
and audit; any "misses" are due to human error, not some grand plan.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251112173944.1380633-5-seanjc%40google.com

1 files changed, 11 insertions, 10 deletions

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index e88eacb1b5bb..da233f20ae6f 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -18,6 +18,7 @@
 #include <uapi/asm/kvm.h>
 
 #include <linux/hardirq.h>
+#include <linux/kvm_types.h>
 #include <linux/pkeys.h>
 #include <linux/vmalloc.h>
 
@@ -276,7 +277,7 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
 
 	return true;
 }
-EXPORT_SYMBOL_GPL(fpu_alloc_guest_fpstate);
+EXPORT_SYMBOL_FOR_KVM(fpu_alloc_guest_fpstate);
 
 void fpu_free_guest_fpstate(struct fpu_guest *gfpu)
 {
@@ -291,7 +292,7 @@ void fpu_free_guest_fpstate(struct fpu_guest *gfpu)
 	gfpu->fpstate = NULL;
 	vfree(fpstate);
 }
-EXPORT_SYMBOL_GPL(fpu_free_guest_fpstate);
+EXPORT_SYMBOL_FOR_KVM(fpu_free_guest_fpstate);
 
 /*
   * fpu_enable_guest_xfd_features - Check xfeatures against guest perm and enable
@@ -313,7 +314,7 @@ int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures)
 
 	return __xfd_enable_feature(xfeatures, guest_fpu);
 }
-EXPORT_SYMBOL_GPL(fpu_enable_guest_xfd_features);
+EXPORT_SYMBOL_FOR_KVM(fpu_enable_guest_xfd_features);
 
 #ifdef CONFIG_X86_64
 void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd)
@@ -324,7 +325,7 @@ void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd)
 		xfd_update_state(guest_fpu->fpstate);
 	fpregs_unlock();
 }
-EXPORT_SYMBOL_GPL(fpu_update_guest_xfd);
+EXPORT_SYMBOL_FOR_KVM(fpu_update_guest_xfd);
 
 /**
  * fpu_sync_guest_vmexit_xfd_state - Synchronize XFD MSR and software state
@@ -348,7 +349,7 @@ void fpu_sync_guest_vmexit_xfd_state(void)
 		__this_cpu_write(xfd_state, fpstate->xfd);
 	}
 }
-EXPORT_SYMBOL_GPL(fpu_sync_guest_vmexit_xfd_state);
+EXPORT_SYMBOL_FOR_KVM(fpu_sync_guest_vmexit_xfd_state);
 #endif /* CONFIG_X86_64 */
 
 int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
@@ -390,7 +391,7 @@ int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
 	fpregs_unlock();
 	return 0;
 }
-EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpstate);
+EXPORT_SYMBOL_FOR_KVM(fpu_swap_kvm_fpstate);
 
 void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
 				    unsigned int size, u64 xfeatures, u32 pkru)
@@ -409,7 +410,7 @@ void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
 		ustate->xsave.header.xfeatures = XFEATURE_MASK_FPSSE;
 	}
 }
-EXPORT_SYMBOL_GPL(fpu_copy_guest_fpstate_to_uabi);
+EXPORT_SYMBOL_FOR_KVM(fpu_copy_guest_fpstate_to_uabi);
 
 int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf,
 				   u64 xcr0, u32 *vpkru)
@@ -439,7 +440,7 @@ int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf,
 
 	return copy_uabi_from_kernel_to_xstate(kstate, ustate, vpkru);
 }
-EXPORT_SYMBOL_GPL(fpu_copy_uabi_to_guest_fpstate);
+EXPORT_SYMBOL_FOR_KVM(fpu_copy_uabi_to_guest_fpstate);
 #endif /* CONFIG_KVM */
 
 void kernel_fpu_begin_mask(unsigned int kfpu_mask)
@@ -857,7 +858,7 @@ void switch_fpu_return(void)
 
 	fpregs_restore_userregs();
 }
-EXPORT_SYMBOL_GPL(switch_fpu_return);
+EXPORT_SYMBOL_FOR_KVM(switch_fpu_return);
 
 void fpregs_lock_and_load(void)
 {
@@ -892,7 +893,7 @@ void fpregs_assert_state_consistent(void)
 
 	WARN_ON_FPU(!fpregs_state_valid(fpu, smp_processor_id()));
 }
-EXPORT_SYMBOL_GPL(fpregs_assert_state_consistent);
+EXPORT_SYMBOL_FOR_KVM(fpregs_assert_state_consistent);
 #endif
 
 void fpregs_mark_activate(void)