Standardize KVM's include paths across all architectures by declaring
the KVM-specific includes in the common Makefile.kvm.  Having common KVM
"own" the included paths reduces the temptation to unnecessarily add
virt/kvm to arch include paths, and conversely if allowing arch code to
grab headers from virt/kvm becomes desirable, virt/kvm can be added to
all architecture's include path with a single line update.

Having the common KVM makefile append to ccflags also provides a
convenient location to append other things, e.g. KVM-specific #defines.

Note, this changes the behavior of s390 and PPC, as s390 and PPC
previously overwrote ccflags-y instead of adding on.  There is no evidence
that overwriting ccflags-y was necessary or even deliberate, as both s390
and PPC switched to the overwrite behavior without so much as a passing
mention when EXTRA_CFLAGS was replaced with ccflags-y (commit c73028a02887
("s390: change to new flag variable") and commit 4108d9ba9091
("powerpc/Makefiles: Change to new flag variables")).

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/arm64/kvm/Makefile   | 2 --
 arch/mips/kvm/Makefile    | 2 --
 arch/powerpc/kvm/Makefile | 2 --
 arch/riscv/kvm/Makefile   | 2 --
 arch/s390/kvm/Makefile    | 2 --
 arch/x86/kvm/Makefile     | 1 -
 virt/kvm/Makefile.kvm     | 2 ++
 7 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index c0c050e53157..3996489baeef 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile

@@ -3,8 +3,6 @@
 # Makefile for Kernel-based Virtual Machine module
 #
 
-ccflags-y += -I $(srctree)/$(src)
-
 include $(srctree)/virt/kvm/Makefile.kvm
 
 obj-$(CONFIG_KVM) += kvm.o

diff --git a/arch/mips/kvm/Makefile b/arch/mips/kvm/Makefile
index 96a7cd21b140..d198e1addea7 100644
--- a/arch/mips/kvm/Makefile
+++ b/arch/mips/kvm/Makefile

@@ -4,8 +4,6 @@
 
 include $(srctree)/virt/kvm/Makefile.kvm
 
-ccflags-y += -Iarch/mips/kvm
-
 kvm-$(CONFIG_CPU_HAS_MSA) += msa.o
 
 kvm-y +=    mips.o emulate.o entry.o \

diff --git a/arch/powerpc/kvm/Makefile b/arch/powerpc/kvm/Makefile
index 08a0e53d58c7..d6c6678ddf65 100644
--- a/arch/powerpc/kvm/Makefile
+++ b/arch/powerpc/kvm/Makefile

@@ -3,8 +3,6 @@
 # Makefile for Kernel-based Virtual Machine module
 #
 
-ccflags-y := -Iarch/powerpc/kvm
-
 include $(srctree)/virt/kvm/Makefile.kvm
 
 common-objs-y += powerpc.o emulate_loadstore.o

diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index 4c2067fc59fc..ff7d5f67e229 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile

@@ -3,8 +3,6 @@
 # Makefile for RISC-V KVM support
 #
 
-ccflags-y += -I $(srctree)/$(src)
-
 include $(srctree)/virt/kvm/Makefile.kvm
 
 obj-$(CONFIG_KVM) += kvm.o

diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
index f17249ab2a72..f8153189e003 100644
--- a/arch/s390/kvm/Makefile
+++ b/arch/s390/kvm/Makefile

@@ -5,8 +5,6 @@
 
 include $(srctree)/virt/kvm/Makefile.kvm
 
-ccflags-y := -Iarch/s390/kvm
-
 kvm-y += kvm-s390.o intercept.o interrupt.o priv.o sigp.o
 kvm-y += diag.o gaccess.o guestdbg.o vsie.o pv.o
 

diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 80e3fe184d17..d13f1a7b7b3d 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile

@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 
-ccflags-y += -I $(srctree)/arch/x86/kvm
 ccflags-$(CONFIG_KVM_WERROR) += -Werror
 
 ifeq ($(CONFIG_FRAME_POINTER),y)

diff --git a/virt/kvm/Makefile.kvm b/virt/kvm/Makefile.kvm
index 29373b59d89a..e85079ad245d 100644
--- a/virt/kvm/Makefile.kvm
+++ b/virt/kvm/Makefile.kvm

@@ -3,6 +3,8 @@
 # Makefile for Kernel-based Virtual Machine module
 #
 
+ccflags-y += -I$(srctree)/$(src)
+
 KVM ?= ../../../virt/kvm
 
 kvm-y := $(KVM)/kvm_main.o $(KVM)/eventfd.o $(KVM)/binary_stats.o

-- 
2.42.0.459.ge4e396fd5e-goog