Re: [PATCH v9 02/24] KVM: Move architecture capability Kconfigs to header defines

[Paolo Bonzini <pbonzini@redhat.com>]

On 9/30/26 19:34, Steffen Eiden wrote:
> Historically, KVM feature opt-ins and callbacks were configured globally
> via Kconfig symbols (CONFIG_HAVE_KVM_* and CONFIG_KVM_*).

Not all of them - there are many __KVM_HAVE_* symbols already.  In 
particular now there's both KVM_MSI and __KVM_HAVE_MSI/__KVM_HAVE_MSIX 
(but the latter is dead, so I have sent a patch to remove it).

There are several remaining CONFIG_HAVE_KVM_ARCH_* Kconfig symbols as 
well.  That's okay, but it should be noted in the changelog that not all 
symbols were fixed.

Can you at least quickly provide a v2, that changes all symbols to 
__KVM_HAVE_<function-name> (and when not applicable __KVM_*, for example 
__KVM_HAVE_READONLY_MEM)?  I have already changed KVM_NO_MMIO to 
__KVM_NO_MMIO in kvm/queue.

Thanks,

Paolo

> Replace these global Kconfig options with architecture-specific opt-in
> defines in <asm/kvm_host.h> and standardize their naming by dropping the
> HAVE_ prefix:
>    - KVM_INVALID_WAKEUPS
>    - KVM_MSI			(formerly HAVE_KVM_MSI)
>    - KVM_NO_POLL			(formerly HAVE_KVM_NO_POLL)
>    - KVM_READONLY_MEM		(formerly HAVE_KVM_READONLY_MEM)
>    - KVM_VCPU_RUN_PID_CHANGE	(formerly HAVE_KVM_VCPU_RUN_PID_CHANGE)
> 
> This allows each architecture and guest implementation to configure its
> supported capabilities independently in its kvm_host header and eliminates
> unnecessary fallback stubs across different KVM targets.
> 
> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
> ---
>   arch/arm64/include/asm/kvm_host.h     |  3 +++
>   arch/arm64/kvm/Kconfig                |  3 ---
>   arch/loongarch/include/asm/kvm_host.h |  2 ++
>   arch/loongarch/kvm/Kconfig            |  2 --
>   arch/mips/include/asm/kvm_host.h      |  1 +
>   arch/mips/kvm/Kconfig                 |  1 -
>   arch/powerpc/include/asm/kvm_host.h   |  3 +++
>   arch/powerpc/kvm/Kconfig              |  1 -
>   arch/riscv/include/asm/kvm_host.h     |  2 ++
>   arch/riscv/kvm/Kconfig                |  2 --
>   arch/s390/include/asm/kvm_host_s390.h |  3 +++
>   arch/s390/kvm/Kconfig                 |  2 --
>   arch/x86/include/asm/kvm_host.h       |  3 +++
>   arch/x86/kvm/Kconfig                  |  3 ---
>   include/linux/kvm_host.h              | 18 +++++++++++-------
>   virt/kvm/Kconfig                      | 15 ---------------
>   virt/kvm/kvm_main.c                   |  4 ++--
>   17 files changed, 30 insertions(+), 38 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index cd9b9d2462f9..db002e5ac9d4 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -30,6 +30,9 @@
>   #include <asm/vncr_mapping.h>
>   
>   #define __KVM_HAVE_ARCH_INTC_INITIALIZED
> +#define KVM_MSI
> +#define KVM_READONLY_MEM
> +#define KVM_VCPU_RUN_PID_CHANGE
>   
>   #define KVM_HALT_POLL_NS_DEFAULT 500000
>   
> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> index 449154f9a485..7329124deb2f 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -28,12 +28,9 @@ menuconfig KVM
>   	select KVM_VFIO
>   	select HAVE_KVM_DIRTY_RING_ACQ_REL
>   	select NEED_KVM_DIRTY_RING_WITH_BITMAP
> -	select HAVE_KVM_MSI
>   	select HAVE_KVM_IRQCHIP
>   	select HAVE_KVM_IRQ_ROUTING
>   	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
>   	select KVM_GUEST_MEMFD
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> index 65d91c3ce313..4cb370a8d09b 100644
> --- a/arch/loongarch/include/asm/kvm_host.h
> +++ b/arch/loongarch/include/asm/kvm_host.h
> @@ -26,6 +26,8 @@
>   #include <asm/loongarch.h>
>   
>   #define __KVM_HAVE_ARCH_INTC_INITIALIZED
> +#define KVM_MSI
> +#define KVM_READONLY_MEM
>   
>   /* Loongarch KVM register ids */
>   #define KVM_GET_IOC_CSR_IDX(id)		((id & KVM_CSR_IDX_MASK) >> LOONGARCH_REG_SHIFT)
> diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
> index 15da2d88c0c1..a427429a2b05 100644
> --- a/arch/loongarch/kvm/Kconfig
> +++ b/arch/loongarch/kvm/Kconfig
> @@ -23,8 +23,6 @@ config KVM
>   	select HAVE_KVM_DIRTY_RING_ACQ_REL
>   	select HAVE_KVM_IRQ_ROUTING
>   	select HAVE_KVM_IRQCHIP
> -	select HAVE_KVM_MSI
> -	select HAVE_KVM_READONLY_MEM
>   	select KVM_COMMON
>   	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
>   	select KVM_GENERIC_HARDWARE_ENABLING
> diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
> index c14b10821817..8e484bb482ba 100644
> --- a/arch/mips/include/asm/kvm_host.h
> +++ b/arch/mips/include/asm/kvm_host.h
> @@ -893,5 +893,6 @@ static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {}
>   static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
>   
>   #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS
> +#define KVM_READONLY_MEM
>   
>   #endif /* __MIPS_KVM_HOST_H__ */
> diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
> index b1b9a1d67758..c24b872afbcb 100644
> --- a/arch/mips/kvm/Kconfig
> +++ b/arch/mips/kvm/Kconfig
> @@ -24,7 +24,6 @@ config KVM
>   	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
>   	select KVM_MMIO
>   	select KVM_GENERIC_HARDWARE_ENABLING
> -	select HAVE_KVM_READONLY_MEM
>   	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 2d139c807577..ad7c34e9b227 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -49,6 +49,9 @@
>   #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
>   
>   #define __KVM_HAVE_ARCH_INTC_INITIALIZED
> +#ifdef CONFIG_KVM_MPIC
> +#define KVM_MSI
> +#endif
>   
>   #define KVM_HALT_POLL_NS_DEFAULT 10000	/* 10 us */
>   
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index b6bc2fc86dca..1fae2de8fa68 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -232,7 +232,6 @@ config KVM_MPIC
>   	depends on KVM && PPC_E500
>   	select HAVE_KVM_IRQCHIP
>   	select HAVE_KVM_IRQ_ROUTING
> -	select HAVE_KVM_MSI
>   	help
>   	  Enable support for emulating MPIC devices inside the
>   	  host kernel, rather than relying on userspace to emulate.
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index a30600579231..23b5560e97ba 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -47,6 +47,8 @@
>   #define KVM_REQ_STEAL_UPDATE		KVM_ARCH_REQ(6)
>   
>   #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
> +#define KVM_MSI
> +#define KVM_READONLY_MEM
>   
>   #define KVM_HAVE_MMU_RWLOCK
>   
> diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
> index ec2cee0a39e0..3cb4f8037300 100644
> --- a/arch/riscv/kvm/Kconfig
> +++ b/arch/riscv/kvm/Kconfig
> @@ -22,8 +22,6 @@ config KVM
>   	depends on RISCV_SBI && MMU
>   	select HAVE_KVM_IRQCHIP
>   	select HAVE_KVM_IRQ_ROUTING
> -	select HAVE_KVM_MSI
> -	select HAVE_KVM_READONLY_MEM
>   	select HAVE_KVM_DIRTY_RING_ACQ_REL
>   	select KVM_COMMON
>   	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> diff --git a/arch/s390/include/asm/kvm_host_s390.h b/arch/s390/include/asm/kvm_host_s390.h
> index 9519b8028b10..bd42c84b8b16 100644
> --- a/arch/s390/include/asm/kvm_host_s390.h
> +++ b/arch/s390/include/asm/kvm_host_s390.h
> @@ -34,6 +34,9 @@
>   
>   #define KVM_INTERNAL_MEM_SLOTS 1
>   
> +#define KVM_INVALID_WAKEUPS
> +#define KVM_NO_POLL
> +
>   #define KVM_S390_MANAGES_S390_GUEST 1
>   
>   /*
> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> index 8d3ee17a1bcb..9045ae20fd89 100644
> --- a/arch/s390/kvm/Kconfig
> +++ b/arch/s390/kvm/Kconfig
> @@ -25,8 +25,6 @@ config KVM
>   	select KVM_COMMON
>   	select HAVE_KVM_IRQCHIP
>   	select HAVE_KVM_IRQ_ROUTING
> -	select HAVE_KVM_INVALID_WAKEUPS
> -	select HAVE_KVM_NO_POLL
>   	select KVM_VFIO
>   	select VIRT_XFER_TO_GUEST_WORK
>   	select KVM_MMU_LOCKLESS_AGING
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e460073ff176..d8f6333de323 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -47,6 +47,9 @@
>   #define kvm_file_to_kvm_arch x86
>   
>   #define __KVM_HAVE_ARCH_VCPU_DEBUGFS
> +#define KVM_MSI
> +#define KVM_NO_POLL
> +#define KVM_READONLY_MEM
>   
>   /*
>    * CONFIG_KVM_MAX_NR_VCPUS is defined iff CONFIG_KVM!=n, provide a dummy max if
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index 538ed1e80332..294684b217bb 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -28,7 +28,6 @@ config KVM_X86
>   	select HAVE_KVM_DIRTY_RING_ACQ_REL
>   	select HAVE_KVM_IRQ_BYPASS
>   	select HAVE_KVM_IRQ_ROUTING
> -	select HAVE_KVM_READONLY_MEM
>   	select VHOST_TASK
>   	select KVM_ASYNC_PF
>   	select USER_RETURN_NOTIFIER
> @@ -37,9 +36,7 @@ config KVM_X86
>   	select PERF_EVENTS
>   	select GUEST_PERF_EVENTS
>   	select PERF_GUEST_MEDIATED_PMU
> -	select HAVE_KVM_MSI
>   	select HAVE_KVM_CPU_RELAX_INTERCEPT
> -	select HAVE_KVM_NO_POLL
>   	select VIRT_XFER_TO_GUEST_WORK
>   	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
>   	select KVM_VFIO
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 160e3e64ec6d..a0e9cc55a6a4 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -750,7 +750,11 @@ static inline u64 kvm_gmem_get_supported_flags(struct kvm *kvm)
>   #ifndef kvm_arch_has_readonly_mem
>   static inline bool kvm_arch_has_readonly_mem(struct kvm *kvm)
>   {
> -	return IS_ENABLED(CONFIG_HAVE_KVM_READONLY_MEM);
> +#ifdef KVM_READONLY_MEM
> +	return true;
> +#else
> +	return false;
> +#endif
>   }
>   #endif
>   
> @@ -2486,7 +2490,7 @@ void kvm_arch_update_irqfd_routing(struct kvm_kernel_irqfd *irqfd,
>   				   struct kvm_kernel_irq_routing_entry *new);
>   #endif /* CONFIG_HAVE_KVM_IRQ_BYPASS */
>   
> -#ifdef CONFIG_HAVE_KVM_INVALID_WAKEUPS
> +#ifdef KVM_INVALID_WAKEUPS
>   /* If we wakeup during the poll time, was it a sucessful poll? */
>   static inline bool vcpu_valid_wakeup(struct kvm_vcpu *vcpu)
>   {
> @@ -2498,9 +2502,9 @@ static inline bool vcpu_valid_wakeup(struct kvm_vcpu *vcpu)
>   {
>   	return true;
>   }
> -#endif /* CONFIG_HAVE_KVM_INVALID_WAKEUPS */
> +#endif /* KVM_INVALID_WAKEUPS */
>   
> -#ifdef CONFIG_HAVE_KVM_NO_POLL
> +#ifdef KVM_NO_POLL
>   /* Callback that tells if we must not poll */
>   bool kvm_arch_no_poll(struct kvm_vcpu *vcpu);
>   #else
> @@ -2508,18 +2512,18 @@ static inline bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
>   {
>   	return false;
>   }
> -#endif /* CONFIG_HAVE_KVM_NO_POLL */
> +#endif /* KVM_NO_POLL */
>   
>   void kvm_arch_guest_memory_reclaimed(struct kvm *kvm);
>   
> -#ifdef CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE
> +#ifdef KVM_VCPU_RUN_PID_CHANGE
>   int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu);
>   #else
>   static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
>   {
>   	return 0;
>   }
> -#endif /* CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE */
> +#endif /* KVM_VCPU_RUN_PID_CHANGE */
>   
>   #ifdef CONFIG_VIRT_XFER_TO_GUEST_WORK
>   static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index c3c0ee253fc7..f3d7f66746c8 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -50,21 +50,12 @@ config KVM_ASYNC_PF
>   config KVM_ASYNC_PF_SYNC
>          bool
>   
> -config HAVE_KVM_MSI
> -       bool
> -
> -config HAVE_KVM_READONLY_MEM
> -       bool
> -
>   config HAVE_KVM_CPU_RELAX_INTERCEPT
>          bool
>   
>   config KVM_VFIO
>          bool
>   
> -config HAVE_KVM_INVALID_WAKEUPS
> -       bool
> -
>   config KVM_GENERIC_DIRTYLOG_READ_PROTECT
>          bool
>   
> @@ -79,12 +70,6 @@ config HAVE_KVM_IRQ_BYPASS
>          tristate
>          select IRQ_BYPASS_MANAGER
>   
> -config HAVE_KVM_VCPU_RUN_PID_CHANGE
> -       bool
> -
> -config HAVE_KVM_NO_POLL
> -       bool
> -
>   config VIRT_XFER_TO_GUEST_WORK
>          bool
>   
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index f62901b7e23d..cd2d752816ab 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4916,7 +4916,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
>   	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
>   	case KVM_CAP_JOIN_MEMORY_REGIONS_WORKS:
>   	case KVM_CAP_INTERNAL_ERROR_DATA:
> -#ifdef CONFIG_HAVE_KVM_MSI
> +#ifdef KVM_MSI
>   	case KVM_CAP_SIGNAL_MSI:
>   #endif
>   #ifdef CONFIG_HAVE_KVM_IRQCHIP
> @@ -5306,7 +5306,7 @@ static long kvm_vm_ioctl(struct file *filp,
>   		r = kvm_ioeventfd(kvm, &data);
>   		break;
>   	}
> -#ifdef CONFIG_HAVE_KVM_MSI
> +#ifdef KVM_MSI
>   	case KVM_SIGNAL_MSI: {
>   		struct kvm_msi msi;
>