[RFC PATCH v2 19/28] KVM: Remove KVM_MMIO as config option

Steffen Eiden
2026-04-28T16:06:05Z

Defining KVM_MMIO is not flexible enough for multi-KVM systems with
different Kconfig options regarding KVM_MMIO. Therefore, remove KVM_MMIO
from the config space and use the macro HAVE_KVM_MMIO instead.

Suggested-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
arch/arm64/include/asm/kvm_host.h | 2 ++
arch/arm64/kvm/Kconfig | 1 -
arch/loongarch/include/asm/kvm_host.h | 2 ++
arch/loongarch/kvm/Kconfig | 1 -
arch/mips/include/asm/kvm_host.h | 2 ++
arch/mips/kvm/Kconfig | 1 -
arch/powerpc/include/asm/kvm_host.h | 7 +++++++
arch/powerpc/kvm/Kconfig | 4 ----
arch/riscv/include/asm/kvm_host.h | 2 ++
arch/riscv/kvm/Kconfig | 1 -
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/Kconfig | 1 -
include/linux/kvm_host.h | 2 +-
virt/kvm/Kconfig | 3 ---
virt/kvm/Makefile.kvm | 3 +--
virt/kvm/coalesced_mmio.c | 3 +++
virt/kvm/coalesced_mmio.h | 2 +-
virt/kvm/kvm_main.c | 8 ++++----
18 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e3a2ac3979ac..39630e235a36 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -33,6 +33,8 @@

#define KVM_HALT_POLL_NS_DEFAULT 500000

+#define HAVE_KVM_MMIO
+
#include <kvm/arm_vgic.h>
#include <kvm/arm_arch_timer.h>
#include <kvm/arm_pmu.h>
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 7d1f22fd490b..4761b5e7e75b 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -22,7 +22,6 @@ menuconfig KVM
select KVM_COMMON
select KVM_GENERIC_HARDWARE_ENABLING
select HAVE_KVM_CPU_RELAX_INTERCEPT
- select KVM_MMIO
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select VIRT_XFER_TO_GUEST_WORK
select KVM_VFIO
diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
index 19eb5e5c3984..392e14302453 100644
--- a/arch/loongarch/include/asm/kvm_host.h
+++ b/arch/loongarch/include/asm/kvm_host.h
@@ -26,6 +26,8 @@

#define __KVM_HAVE_ARCH_INTC_INITIALIZED

+#define HAVE_KVM_MMIO
+
/* Loongarch KVM register ids */
#define KVM_GET_IOC_CSR_IDX(id) ((id & KVM_CSR_IDX_MASK) >> LOONGARCH_REG_SHIFT)
#define KVM_GET_IOC_CPUCFG_IDX(id) ((id & KVM_CPUCFG_IDX_MASK) >> LOONGARCH_REG_SHIFT)
diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
index 8e5213609975..a244f2aea7ff 100644
--- a/arch/loongarch/kvm/Kconfig
+++ b/arch/loongarch/kvm/Kconfig
@@ -28,7 +28,6 @@ config KVM
select KVM_COMMON
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_GENERIC_HARDWARE_ENABLING
- select KVM_MMIO
select VIRT_XFER_TO_GUEST_WORK
select SCHED_INFO
select GUEST_PERF_EVENTS if PERF_EVENTS
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index c14b10821817..e3cb7c8c9461 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -26,6 +26,8 @@

#include <kvm/iodev.h>

+#define HAVE_KVM_MMIO
+
/* MIPS KVM register ids */
#define MIPS_CP0_32(_R, _S) \
(KVM_REG_MIPS_CP0 | KVM_REG_SIZE_U32 | (8 * (_R) + (_S)))
diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
index b1b9a1d67758..c65596fdf54f 100644
--- a/arch/mips/kvm/Kconfig
+++ b/arch/mips/kvm/Kconfig
@@ -22,7 +22,6 @@ config KVM
select EXPORT_UASM
select KVM_COMMON
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
- select KVM_MMIO
select KVM_GENERIC_HARDWARE_ENABLING
select HAVE_KVM_READONLY_MEM
help
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 2d139c807577..92d14438e31b 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -29,6 +29,13 @@

#define __KVM_HAVE_ARCH_VCPU_DEBUGFS

+#if defined(CONFIG_KVM_BOOK3S_32_HANDLER) || \
+ defined(CONFIG_KVM_BOOK3S_PR_POSSIBLE) || \
+ defined(CONFIG_KVM_E500V2) || \
+ defined(CONFIG_KVM_E500MC)
+#define HAVE_KVM_MMIO
+#endif
+
#define KVM_MAX_VCPUS NR_CPUS
#define KVM_MAX_VCORES NR_CPUS

diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index 9a0d1c1aca6c..d97a4a51ec55 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -29,7 +29,6 @@ config KVM_BOOK3S_HANDLER
config KVM_BOOK3S_32_HANDLER
bool
select KVM_BOOK3S_HANDLER
- select KVM_MMIO

config KVM_BOOK3S_64_HANDLER
bool
@@ -37,7 +36,6 @@ config KVM_BOOK3S_64_HANDLER

config KVM_BOOK3S_PR_POSSIBLE
bool
- select KVM_MMIO

config KVM_BOOK3S_HV_POSSIBLE
bool
@@ -200,7 +198,6 @@ config KVM_E500V2
depends on PPC_E500 && !PPC_E500MC
depends on !CONTEXT_TRACKING_USER
select KVM
- select KVM_MMIO
help
Support running unmodified E500 guest kernels in virtual machines on
E500v2 host processors.
@@ -215,7 +212,6 @@ config KVM_E500MC
depends on PPC_E500MC
depends on !CONTEXT_TRACKING_USER
select KVM
- select KVM_MMIO
select KVM_BOOKE_HV
help
Support running unmodified E500MC/E5500/E6500 guest kernels in
diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 24585304c02b..a405cd30c6fa 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -25,6 +25,8 @@
#include <asm/kvm_vcpu_timer.h>
#include <asm/kvm_vcpu_pmu.h>

+#define HAVE_KVM_MMIO
+
#define KVM_MAX_VCPUS 1024

#define KVM_HALT_POLL_NS_DEFAULT 500000
diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index ec2cee0a39e0..3aea8d4939d2 100644
--- a/arch/riscv/kvm/Kconfig
+++ b/arch/riscv/kvm/Kconfig
@@ -28,7 +28,6 @@ config KVM
select KVM_COMMON
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_GENERIC_HARDWARE_ENABLING
- select KVM_MMIO
select VIRT_XFER_TO_GUEST_WORK
select SCHED_INFO
select GUEST_PERF_EVENTS if PERF_EVENTS
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6e4e3ef9b8c7..4cdaf60c9217 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -45,6 +45,8 @@

#define __KVM_HAVE_ARCH_VCPU_DEBUGFS

+#define HAVE_KVM_MMIO
+
/*
* CONFIG_KVM_MAX_NR_VCPUS is defined iff CONFIG_KVM!=n, provide a dummy max if
* KVM is disabled (arbitrarily use the default from CONFIG_KVM_MAX_NR_VCPUS).
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 801bf9e520db..da5d9fa8a11c 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -32,7 +32,6 @@ config KVM_X86
select VHOST_TASK
select KVM_ASYNC_PF
select USER_RETURN_NOTIFIER
- select KVM_MMIO
select SCHED_INFO
select PERF_EVENTS
select GUEST_PERF_EVENTS
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 44e6fe3d2d80..2aeda4c6af14 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -833,7 +833,7 @@ struct kvm {
struct list_head ioeventfds;
struct kvm_vm_stat stat;
struct kvm_arch arch;
-#ifdef CONFIG_KVM_MMIO
+#ifdef HAVE_KVM_MMIO
struct kvm_coalesced_mmio_ring *coalesced_mmio_ring;
spinlock_t ring_lock;
struct list_head coalesced_zones;
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 794976b88c6f..c4a983e41765 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -40,9 +40,6 @@ config NEED_KVM_DIRTY_RING_WITH_BITMAP
bool
depends on HAVE_KVM_DIRTY_RING

-config KVM_MMIO
- bool
-
config KVM_ASYNC_PF
bool

diff --git a/virt/kvm/Makefile.kvm b/virt/kvm/Makefile.kvm
index d047d4cf58c9..3c27c18b49a0 100644
--- a/virt/kvm/Makefile.kvm
+++ b/virt/kvm/Makefile.kvm
@@ -5,9 +5,8 @@

KVM ?= ../../../virt/kvm

-kvm-y := $(KVM)/kvm_main.o $(KVM)/eventfd.o $(KVM)/binary_stats.o
+kvm-y := $(KVM)/kvm_main.o $(KVM)/eventfd.o $(KVM)/binary_stats.o $(KVM)/coalesced_mmio.o
kvm-$(CONFIG_KVM_VFIO) += $(KVM)/vfio.o
-kvm-$(CONFIG_KVM_MMIO) += $(KVM)/coalesced_mmio.o
kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o
kvm-$(CONFIG_HAVE_KVM_IRQ_ROUTING) += $(KVM)/irqchip.o
kvm-$(CONFIG_HAVE_KVM_DIRTY_RING) += $(KVM)/dirty_ring.o
diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index 6b1d90161099..070eba3c6534 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -12,6 +12,8 @@
#include <kvm/iodev.h>

#include <linux/kvm_host.h>
+
+#ifdef HAVE_KVM_MMIO
#include <linux/slab.h>
#include <linux/kvm.h>

@@ -188,3 +190,4 @@ int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
*/
return 0;
}
+#endif /* ifdef HAVE_KVM_MMIO */
diff --git a/virt/kvm/coalesced_mmio.h b/virt/kvm/coalesced_mmio.h
index 36f84264ed25..a8430d41945b 100644
--- a/virt/kvm/coalesced_mmio.h
+++ b/virt/kvm/coalesced_mmio.h
@@ -11,7 +11,7 @@
*
*/

-#ifdef CONFIG_KVM_MMIO
+#ifdef HAVE_KVM_MMIO

#include <linux/list.h>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 60a5bb778993..ab3a0347bdd3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4041,7 +4041,7 @@ static vm_fault_t kvm_vcpu_fault(struct vm_fault *vmf)
else if (vmf->pgoff == KVM_PIO_PAGE_OFFSET)
page = virt_to_page(vcpu->arch.pio_data);
#endif
-#ifdef CONFIG_KVM_MMIO
+#ifdef HAVE_KVM_MMIO
else if (vmf->pgoff == KVM_COALESCED_MMIO_PAGE_OFFSET)
page = virt_to_page(vcpu->kvm->coalesced_mmio_ring);
#endif
@@ -4867,7 +4867,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
case KVM_CAP_ENABLE_CAP_VM:
case KVM_CAP_HALT_POLL:
return 1;
-#ifdef CONFIG_KVM_MMIO
+#ifdef HAVE_KVM_MMIO
case KVM_CAP_COALESCED_MMIO:
return KVM_COALESCED_MMIO_PAGE_OFFSET;
case KVM_CAP_COALESCED_PIO:
@@ -5208,7 +5208,7 @@ static long kvm_vm_ioctl(struct file *filp,
break;
}
#endif
-#ifdef CONFIG_KVM_MMIO
+#ifdef HAVE_KVM_MMIO
case KVM_REGISTER_COALESCED_MMIO: {
struct kvm_coalesced_mmio_zone zone;

@@ -5530,7 +5530,7 @@ static long kvm_dev_ioctl(struct file *filp,
#ifdef CONFIG_X86
r += PAGE_SIZE; /* pio data page */
#endif
-#ifdef CONFIG_KVM_MMIO
+#ifdef HAVE_KVM_MMIO
r += PAGE_SIZE; /* coalesced mmio ring page */
#endif
break;
--
2.51.0