Re: [PATCH 06/26] KVM: Drop CONFIG_KVM_VFIO and just look at KVM+VFIO

Alex Williamson
2023-09-28T22:23:07Z

On Fri, 15 Sep 2023 17:30:58 -0700
Sean Christopherson <seanjc@google.com> wrote:

> Drop KVM's KVM_VFIO Kconfig, and instead compile in VFIO support if
> and only if VFIO itself is enabled. Similar to the recent change to have
> VFIO stop looking at HAVE_KVM, compiling in support for talking to VFIO
> just because the architecture supports VFIO is nonsensical.
>
> This fixes a bug where RISC-V doesn't select KVM_VFIO, i.e. would silently
> fail to do connect KVM and VFIO, even though RISC-V supports VFIO. The
> bug is benign as the only driver in all of Linux that actually uses the
> KVM reference provided by VFIO is KVM-GT, which is x86/Intel specific.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/arm64/kvm/Kconfig | 1 -
> arch/powerpc/kvm/Kconfig | 1 -
> arch/s390/kvm/Kconfig | 1 -
> arch/x86/kvm/Kconfig | 1 -
> virt/kvm/Kconfig | 3 ---
> virt/kvm/Makefile.kvm | 4 +++-
> virt/kvm/vfio.h | 2 +-
> 7 files changed, 4 insertions(+), 9 deletions(-)

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>

> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> index 83c1e09be42e..2b5c332f157d 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -28,7 +28,6 @@ menuconfig KVM
> select KVM_MMIO
> select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> select KVM_XFER_TO_GUEST_WORK
> - select KVM_VFIO
> select HAVE_KVM_EVENTFD
> select HAVE_KVM_IRQFD
> select HAVE_KVM_DIRTY_RING_ACQ_REL
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index 902611954200..c4beb49c0eb2 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -22,7 +22,6 @@ config KVM
> select PREEMPT_NOTIFIERS
> select HAVE_KVM_EVENTFD
> select HAVE_KVM_VCPU_ASYNC_IOCTL
> - select KVM_VFIO
> select IRQ_BYPASS_MANAGER
> select HAVE_KVM_IRQ_BYPASS
> select INTERVAL_TREE
> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> index 45fdf2a9b2e3..459d536116a6 100644
> --- a/arch/s390/kvm/Kconfig
> +++ b/arch/s390/kvm/Kconfig
> @@ -31,7 +31,6 @@ config KVM
> select HAVE_KVM_IRQ_ROUTING
> select HAVE_KVM_INVALID_WAKEUPS
> select HAVE_KVM_NO_POLL
> - select KVM_VFIO
> select INTERVAL_TREE
> select MMU_NOTIFIER
> help
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index ed90f148140d..0f01e5600b5f 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -45,7 +45,6 @@ config KVM
> select HAVE_KVM_NO_POLL
> select KVM_XFER_TO_GUEST_WORK
> select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> - select KVM_VFIO
> select INTERVAL_TREE
> select HAVE_KVM_PM_NOTIFIER if PM
> select KVM_GENERIC_HARDWARE_ENABLING
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index 484d0873061c..f0be3b55cea6 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -59,9 +59,6 @@ config HAVE_KVM_MSI
> config HAVE_KVM_CPU_RELAX_INTERCEPT
> bool
>
> -config KVM_VFIO
> - bool
> -
> config HAVE_KVM_INVALID_WAKEUPS
> bool
>
> diff --git a/virt/kvm/Makefile.kvm b/virt/kvm/Makefile.kvm
> index 2c27d5d0c367..29373b59d89a 100644
> --- a/virt/kvm/Makefile.kvm
> +++ b/virt/kvm/Makefile.kvm
> @@ -6,7 +6,9 @@
> KVM ?= ../../../virt/kvm
>
> kvm-y := $(KVM)/kvm_main.o $(KVM)/eventfd.o $(KVM)/binary_stats.o
> -kvm-$(CONFIG_KVM_VFIO) += $(KVM)/vfio.o
> +ifdef CONFIG_VFIO
> +kvm-y += $(KVM)/vfio.o
> +endif
> kvm-$(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
> diff --git a/virt/kvm/vfio.h b/virt/kvm/vfio.h
> index e130a4a03530..af475a323965 100644
> --- a/virt/kvm/vfio.h
> +++ b/virt/kvm/vfio.h
> @@ -2,7 +2,7 @@
> #ifndef __KVM_VFIO_H
> #define __KVM_VFIO_H
>
> -#ifdef CONFIG_KVM_VFIO
> +#if IS_ENABLED(CONFIG_KVM) && IS_ENABLED(CONFIG_VFIO)
> int kvm_vfio_ops_init(void);
> void kvm_vfio_ops_exit(void);
> #else