kvm: replace __KVM_HAVE_READONLY_MEM with Kconfig symbol

KVM uses __KVM_HAVE_* symbols in the architecture-dependent uapi/asm/kvm.h to mask
unused definitions in include/uapi/linux/kvm.h.  __KVM_HAVE_READONLY_MEM however
was nothing but a misguided attempt to define KVM_CAP_READONLY_MEM only on
architectures where KVM_CHECK_EXTENSION(KVM_CAP_READONLY_MEM) could possibly
return nonzero.  This however does not make sense, and it prevented userspace
from supporting this architecture-independent feature without recompilation.

Therefore, these days __KVM_HAVE_READONLY_MEM does not mask anything and
is only used in virt/kvm/kvm_main.c.  Userspace does not need to test it
and there should be no need for it to exist.  Remove it and replace it
with a Kconfig symbol within Linux source code.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/arm64/include/uapi/asm/kvm.h

@@ -39,7 +39,6 @@
 
 #define __KVM_HAVE_GUEST_DEBUG
 #define __KVM_HAVE_IRQ_LINE
-#define __KVM_HAVE_READONLY_MEM
 #define __KVM_HAVE_VCPU_EVENTS
 
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1

arch/arm64/kvm/Kconfig

@@ -36,6 +36,7 @@ menuconfig KVM
 	select HAVE_KVM_IRQ_ROUTING
 	select IRQ_BYPASS_MANAGER
 	select HAVE_KVM_IRQ_BYPASS
+	select HAVE_KVM_READONLY_MEM
 	select HAVE_KVM_VCPU_RUN_PID_CHANGE
 	select SCHED_INFO
 	select GUEST_PERF_EVENTS if PERF_EVENTS

arch/loongarch/include/uapi/asm/kvm.h

@@ -14,8 +14,6 @@
  * Some parts derived from the x86 version of this file.
  */
 
-#define __KVM_HAVE_READONLY_MEM
-
 #define KVM_COALESCED_MMIO_PAGE_OFFSET	1
 #define KVM_DIRTY_LOG_PAGE_OFFSET	64
 

arch/loongarch/kvm/Kconfig

@@ -28,6 +28,7 @@ config KVM
 	select KVM_GENERIC_HARDWARE_ENABLING
 	select KVM_GENERIC_MMU_NOTIFIER
 	select KVM_MMIO
+	select HAVE_KVM_READONLY_MEM
 	select KVM_XFER_TO_GUEST_WORK
 	help
 	  Support hosting virtualized guest machines using

arch/mips/include/uapi/asm/kvm.h

@@ -20,8 +20,6 @@
  * Some parts derived from the x86 version of this file.
  */
 
-#define __KVM_HAVE_READONLY_MEM
-
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
 
 /*

arch/mips/kvm/Kconfig

@@ -26,6 +26,7 @@ config KVM
 	select KVM_MMIO
 	select KVM_GENERIC_MMU_NOTIFIER
 	select KVM_GENERIC_HARDWARE_ENABLING
+	select HAVE_KVM_READONLY_MEM
 	help
 	  Support for hosting Guest kernels.
 

arch/riscv/include/uapi/asm/kvm.h

@@ -16,7 +16,6 @@
 #include <asm/ptrace.h>
 
 #define __KVM_HAVE_IRQ_LINE
-#define __KVM_HAVE_READONLY_MEM
 
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
 

arch/riscv/kvm/Kconfig

@@ -24,6 +24,7 @@ config KVM
 	select HAVE_KVM_IRQ_ROUTING
 	select HAVE_KVM_MSI
 	select HAVE_KVM_VCPU_ASYNC_IOCTL
+	select HAVE_KVM_READONLY_MEM
 	select KVM_COMMON
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_GENERIC_HARDWARE_ENABLING

arch/x86/include/uapi/asm/kvm.h

@@ -51,7 +51,6 @@
 #define __KVM_HAVE_DEBUGREGS
 #define __KVM_HAVE_XSAVE
 #define __KVM_HAVE_XCRS
-#define __KVM_HAVE_READONLY_MEM
 
 /* Architectural interrupt line count. */
 #define KVM_NR_INTERRUPTS 256

arch/x86/kvm/Kconfig

@@ -32,6 +32,7 @@ config KVM
 	select IRQ_BYPASS_MANAGER
 	select HAVE_KVM_IRQ_BYPASS
 	select HAVE_KVM_IRQ_ROUTING
+	select HAVE_KVM_READONLY_MEM
 	select KVM_ASYNC_PF
 	select USER_RETURN_NOTIFIER
 	select KVM_MMIO

virt/kvm/Kconfig

@@ -55,6 +55,9 @@ config KVM_ASYNC_PF_SYNC
 config HAVE_KVM_MSI
        bool
 
+config HAVE_KVM_READONLY_MEM
+       bool
+
 config HAVE_KVM_CPU_RELAX_INTERCEPT
        bool
 

virt/kvm/kvm_main.c

@@ -1614,7 +1614,7 @@ static int check_memory_region_flags(struct kvm *kvm,
 	if (mem->flags & KVM_MEM_GUEST_MEMFD)
 		valid_flags &= ~KVM_MEM_LOG_DIRTY_PAGES;
 
-#ifdef __KVM_HAVE_READONLY_MEM
+#ifdef CONFIG_HAVE_KVM_READONLY_MEM
 	valid_flags |= KVM_MEM_READONLY;
 #endif