KVM: Move x86's version of struct kvm_mmu_memory_cache to common code

Move x86's 'struct kvm_mmu_memory_cache' to common code in anticipation
of moving the entire x86 implementation code to common KVM and reusing
it for arm64 and MIPS.  Add a new architecture specific asm/kvm_types.h
to control the existence and parameters of the struct.  The new header
is needed to avoid a chicken-and-egg problem with asm/kvm_host.h as all
architectures define instances of the struct in their vCPU structs.

Add an asm-generic version of kvm_types.h to avoid having empty files on
PPC and s390 in the long term, and for arm64 and mips in the short term.

Suggested-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200703023545.8771-15-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index 68e84cf42a3f..a7580f69dda0 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -20,6 +20,8 @@ enum kvm_mr_change;
 
 #include <linux/types.h>
 
+#include <asm/kvm_types.h>
+
 /*
  * Address types:
  *
@@ -58,4 +60,21 @@ struct gfn_to_pfn_cache {
 	bool dirty;
 };
 
+#ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
+/*
+ * Memory caches are used to preallocate memory ahead of various MMU flows,
+ * e.g. page fault handlers.  Gracefully handling allocation failures deep in
+ * MMU flows is problematic, as is triggering reclaim, I/O, etc... while
+ * holding MMU locks.  Note, these caches act more like prefetch buffers than
+ * classical caches, i.e. objects are not returned to the cache on being freed.
+ */
+struct kvm_mmu_memory_cache {
+	int nobjs;
+	gfp_t gfp_zero;
+	struct kmem_cache *kmem_cache;
+	void *objects[KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE];
+};
+#endif
+
+
 #endif /* __KVM_TYPES_H__ */