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Date:   Thu, 28 Sep 2023 16:21:11 -0600
From:   Alex Williamson <alex.williamson@redhat.com>
To:     Sean Christopherson <seanjc@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
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Subject: Re: [PATCH 06/26] KVM: Drop CONFIG_KVM_VFIO and just look at
 KVM+VFIO
Message-ID: <20230928162111.09820688.alex.williamson@redhat.com>
In-Reply-To: <20230916003118.2540661-7-seanjc@google.com>
References: <20230916003118.2540661-1-seanjc@google.com>
        <20230916003118.2540661-7-seanjc@google.com>
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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