[PATCH v8 09/29] KVM: Replace CONFIG_KVM_MMIO with KVM_NO_MMIO
From: Steffen Eiden
Date: Fri Sep 18 2026 - 09:56:43 EST
Defining KVM_MMIO is not flexible enough for multi-KVM systems where one
KVM implements MMIO but others do not. Therefore, remove KVM_MMIO from
the config space and use the macro KVM_NO_MMIO instead.
Define KVM_NO_MMIO for KVM/s390 and for selected KVM/powerpc
configurations.
coalesced_mmio.c is now always compiled&linked. However, for
architectures/configurations defining KVM_NO_MMIO this effectively
collapses to an empty object with no mmio code.
No functional changes.
Suggested-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Steffen Eiden <seiden@xxxxxxxxxxxxx>
---
arch/arm64/kvm/Kconfig | 1 -
arch/loongarch/kvm/Kconfig | 1 -
arch/mips/kvm/Kconfig | 1 -
arch/powerpc/include/asm/kvm_host.h | 7 +++++++
arch/powerpc/kvm/Kconfig | 4 ----
arch/riscv/kvm/Kconfig | 1 -
arch/s390/include/asm/kvm_host_s390.h | 2 ++
arch/x86/kvm/Kconfig | 1 -
include/linux/kvm_host.h | 2 +-
virt/kvm/Kconfig | 3 ---
virt/kvm/Makefile.kvm | 4 ++--
virt/kvm/coalesced_mmio.c | 4 ++++
virt/kvm/coalesced_mmio.h | 2 +-
virt/kvm/kvm_main.c | 8 ++++----
14 files changed, 21 insertions(+), 20 deletions(-)
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 7329124deb2f..8475f32ad9e6 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/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
index a427429a2b05..fd387326d2f2 100644
--- a/arch/loongarch/kvm/Kconfig
+++ b/arch/loongarch/kvm/Kconfig
@@ -26,7 +26,6 @@ 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/kvm/Kconfig b/arch/mips/kvm/Kconfig
index c24b872afbcb..849ce7c7c4df 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
help
Support for hosting Guest kernels.
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index ad7c34e9b227..620f163d65a9 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 KVM_NO_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 1fae2de8fa68..cacc22e34afd 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -30,7 +30,6 @@ config KVM_BOOK3S_HANDLER
config KVM_BOOK3S_32_HANDLER
bool
select KVM_BOOK3S_HANDLER
- select KVM_MMIO
config KVM_BOOK3S_64_HANDLER
bool
@@ -38,7 +37,6 @@ config KVM_BOOK3S_64_HANDLER
config KVM_BOOK3S_PR_POSSIBLE
bool
- select KVM_MMIO
config KVM_BOOK3S_HV_POSSIBLE
bool
@@ -201,7 +199,6 @@ 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.
@@ -216,7 +213,6 @@ 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/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index 3cb4f8037300..2e3c4e6c1cd7 100644
--- a/arch/riscv/kvm/Kconfig
+++ b/arch/riscv/kvm/Kconfig
@@ -26,7 +26,6 @@ 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/s390/include/asm/kvm_host_s390.h b/arch/s390/include/asm/kvm_host_s390.h
index 5fd7f49d7c0d..451346f32008 100644
--- a/arch/s390/include/asm/kvm_host_s390.h
+++ b/arch/s390/include/asm/kvm_host_s390.h
@@ -40,6 +40,8 @@
#define KVM_S390_MANAGES_S390_GUEST 1
+#define KVM_NO_MMIO
+
/*
* These seem to be used for allocating ->chip in the routing table, which we
* don't use. 1 is as small as we can get to reduce the needed memory. If we
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index fa20f64d6a2f..82b6c91e763b 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -31,7 +31,6 @@ 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 b7bd20fc9e34..7ebc9aaaec2d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -846,7 +846,7 @@ struct kvm {
struct kvm_vm_stat stat;
struct kvm_arch arch;
refcount_t users_count;
-#ifdef CONFIG_KVM_MMIO
+#ifndef KVM_NO_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 008b110ebdb7..69b47cb6526c 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 ee66d460c494..9a3b05a01c62 100644
--- a/virt/kvm/Makefile.kvm
+++ b/virt/kvm/Makefile.kvm
@@ -10,9 +10,9 @@ KVM_DEV_MINOR ?= KVM_MINOR
ccflags-y +=-DKVM_DEV_NAME=$(KVM_DEV_NAME) -DKVM_DEV_MINOR=$(KVM_DEV_MINOR)
-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..d6cae6855237 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -15,6 +15,8 @@
#include <linux/slab.h>
#include <linux/kvm.h>
+#ifndef KVM_NO_MMIO
+
#include "coalesced_mmio.h"
static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
@@ -188,3 +190,5 @@ int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
*/
return 0;
}
+
+#endif /* !KVM_NO_MMIO */
diff --git a/virt/kvm/coalesced_mmio.h b/virt/kvm/coalesced_mmio.h
index 36f84264ed25..bcaa34fce1e8 100644
--- a/virt/kvm/coalesced_mmio.h
+++ b/virt/kvm/coalesced_mmio.h
@@ -11,7 +11,7 @@
*
*/
-#ifdef CONFIG_KVM_MMIO
+#ifndef KVM_NO_MMIO
#include <linux/list.h>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a7ce1f22b3de..32b8aad8fa2b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4061,7 +4061,7 @@ 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
+#ifndef KVM_NO_MMIO
else if (vmf->pgoff == KVM_COALESCED_MMIO_PAGE_OFFSET)
page = virt_to_page(vcpu->kvm->coalesced_mmio_ring);
#endif
@@ -4902,7 +4902,7 @@ 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
+#ifndef KVM_NO_MMIO
case KVM_CAP_COALESCED_MMIO:
return KVM_COALESCED_MMIO_PAGE_OFFSET;
case KVM_CAP_COALESCED_PIO:
@@ -5243,7 +5243,7 @@ static long kvm_vm_ioctl(struct file *filp,
break;
}
#endif
-#ifdef CONFIG_KVM_MMIO
+#ifndef KVM_NO_MMIO
case KVM_REGISTER_COALESCED_MMIO: {
struct kvm_coalesced_mmio_zone zone;
@@ -5578,7 +5578,7 @@ static long kvm_dev_ioctl(struct file *filp,
#ifdef CONFIG_X86
r += PAGE_SIZE; /* pio data page */
#endif
-#ifdef CONFIG_KVM_MMIO
+#ifndef KVM_NO_MMIO
r += PAGE_SIZE; /* coalesced mmio ring page */
#endif
break;
--
2.53.0