[PATCH 14/21] KVM: Move x86's version of struct kvm_mmu_memory_cache to common code

[Sean Christopherson <sean.j.christopherson@intel.com>]

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.

Suggested-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/arm64/include/asm/kvm_types.h   |  6 ++++++
 arch/mips/include/asm/kvm_types.h    |  5 +++++
 arch/powerpc/include/asm/kvm_types.h |  5 +++++
 arch/s390/include/asm/kvm_types.h    |  5 +++++
 arch/x86/include/asm/kvm_host.h      | 13 -------------
 arch/x86/include/asm/kvm_types.h     |  7 +++++++
 include/linux/kvm_types.h            | 19 +++++++++++++++++++
 7 files changed, 47 insertions(+), 13 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_types.h
 create mode 100644 arch/mips/include/asm/kvm_types.h
 create mode 100644 arch/powerpc/include/asm/kvm_types.h
 create mode 100644 arch/s390/include/asm/kvm_types.h
 create mode 100644 arch/x86/include/asm/kvm_types.h

diff --git a/arch/arm64/include/asm/kvm_types.h b/arch/arm64/include/asm/kvm_types.h
new file mode 100644
index 000000000000..d0987007d581
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_types.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM64_KVM_TYPES_H
+#define _ASM_ARM64_KVM_TYPES_H
+
+#endif /* _ASM_ARM64_KVM_TYPES_H */
+
diff --git a/arch/mips/include/asm/kvm_types.h b/arch/mips/include/asm/kvm_types.h
new file mode 100644
index 000000000000..5efeb32a5926
--- /dev/null
+++ b/arch/mips/include/asm/kvm_types.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_MIPS_KVM_TYPES_H
+#define _ASM_MIPS_KVM_TYPES_H
+
+#endif /* _ASM_MIPS_KVM_TYPES_H */
diff --git a/arch/powerpc/include/asm/kvm_types.h b/arch/powerpc/include/asm/kvm_types.h
new file mode 100644
index 000000000000..f627eceaa314
--- /dev/null
+++ b/arch/powerpc/include/asm/kvm_types.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_POWERPC_KVM_TYPES_H
+#define _ASM_POWERPC_KVM_TYPES_H
+
+#endif /* _ASM_POWERPC_KVM_TYPES_H */
diff --git a/arch/s390/include/asm/kvm_types.h b/arch/s390/include/asm/kvm_types.h
new file mode 100644
index 000000000000..b66a81f8a354
--- /dev/null
+++ b/arch/s390/include/asm/kvm_types.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_KVM_TYPES_H
+#define _ASM_S390_KVM_TYPES_H
+
+#endif /* _ASM_S390_KVM_TYPES_H */
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index fb99e6776e27..8e8fea13b6c7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -193,8 +193,6 @@ struct x86_exception;
 enum x86_intercept;
 enum x86_intercept_stage;
 
-#define KVM_NR_MEM_OBJS 40
-
 #define KVM_NR_DB_REGS	4
 
 #define DR6_BD		(1 << 13)
@@ -245,17 +243,6 @@ enum x86_intercept_stage;
 
 struct kvm_kernel_irq_routing_entry;
 
-/*
- * We don't want allocation failures within the mmu code, so we preallocate
- * enough memory for a single page fault in a cache.
- */
-struct kvm_mmu_memory_cache {
-	int nobjs;
-	gfp_t gfp_zero;
-	struct kmem_cache *kmem_cache;
-	void *objects[KVM_NR_MEM_OBJS];
-};
-
 /*
  * the pages used as guest page table on soft mmu are tracked by
  * kvm_memory_slot.arch.gfn_track which is 16 bits, so the role bits used
diff --git a/arch/x86/include/asm/kvm_types.h b/arch/x86/include/asm/kvm_types.h
new file mode 100644
index 000000000000..08f1b57d3b62
--- /dev/null
+++ b/arch/x86/include/asm/kvm_types.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_KVM_TYPES_H
+#define _ASM_X86_KVM_TYPES_H
+
+#define KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE 40
+
+#endif /* _ASM_X86_KVM_TYPES_H */
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__ */
-- 
2.26.0