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Message-ID: <20251017111241.3ce81f4f@p-imbrenda>
Date: Fri, 17 Oct 2025 11:12:41 +0200
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>,
Huacai Chen <chenhuacai@...nel.org>,
Madhavan Srinivasan
<maddy@...ux.ibm.com>,
Anup Patel <anup@...infault.org>, Paul Walmsley
<pjw@...nel.org>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou
<aou@...s.berkeley.edu>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
Paolo Bonzini <pbonzini@...hat.com>,
"Kirill A. Shutemov" <kas@...nel.org>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
kvm@...r.kernel.org, loongarch@...ts.linux.dev,
linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
x86@...nel.org, linux-coco@...ts.linux.dev,
linux-kernel@...r.kernel.org, Ira Weiny
<ira.weiny@...el.com>,
Kai Huang <kai.huang@...el.com>, Michael Roth
<michael.roth@....com>,
Yan Zhao <yan.y.zhao@...el.com>,
Vishal Annapurve
<vannapurve@...gle.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Ackerley Tng <ackerleytng@...gle.com>,
Binbin Wu
<binbin.wu@...ux.intel.com>
Subject: Re: [PATCH v3 01/25] KVM: Make support for
kvm_arch_vcpu_async_ioctl() mandatory
On Thu, 16 Oct 2025 17:32:19 -0700
Sean Christopherson <seanjc@...gle.com> wrote:
> Implement kvm_arch_vcpu_async_ioctl() "natively" in x86 and arm64 instead
> of relying on an #ifdef'd stub, and drop HAVE_KVM_VCPU_ASYNC_IOCTL in
> anticipation of using the API on x86. Once x86 uses the API, providing a
> stub for one architecture and having all other architectures opt-in
> requires more code than simply implementing the API in the lone holdout.
>
> Eliminating the Kconfig will also reduce churn if the API is renamed in
> the future (spoiler alert).
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Acked-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> ---
> arch/arm64/kvm/arm.c | 6 ++++++
> arch/loongarch/kvm/Kconfig | 1 -
> arch/mips/kvm/Kconfig | 1 -
> arch/powerpc/kvm/Kconfig | 1 -
> arch/riscv/kvm/Kconfig | 1 -
> arch/s390/kvm/Kconfig | 1 -
> arch/x86/kvm/x86.c | 6 ++++++
> include/linux/kvm_host.h | 10 ----------
> virt/kvm/Kconfig | 3 ---
> 9 files changed, 12 insertions(+), 18 deletions(-)
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index f21d1b7f20f8..785aaaee6a5d 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1828,6 +1828,12 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
> return r;
> }
>
> +long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl,
> + unsigned long arg)
> +{
> + return -ENOIOCTLCMD;
> +}
> +
> void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> {
>
> diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
> index ae64bbdf83a7..ed4f724db774 100644
> --- a/arch/loongarch/kvm/Kconfig
> +++ b/arch/loongarch/kvm/Kconfig
> @@ -25,7 +25,6 @@ config KVM
> select HAVE_KVM_IRQCHIP
> select HAVE_KVM_MSI
> select HAVE_KVM_READONLY_MEM
> - select HAVE_KVM_VCPU_ASYNC_IOCTL
> select KVM_COMMON
> select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> select KVM_GENERIC_HARDWARE_ENABLING
> diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
> index ab57221fa4dd..cc13cc35f208 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 HAVE_KVM_VCPU_ASYNC_IOCTL
> select KVM_MMIO
> select KVM_GENERIC_MMU_NOTIFIER
> select KVM_GENERIC_HARDWARE_ENABLING
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index 2f2702c867f7..c9a2d50ff1b0 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -20,7 +20,6 @@ if VIRTUALIZATION
> config KVM
> bool
> select KVM_COMMON
> - select HAVE_KVM_VCPU_ASYNC_IOCTL
> select KVM_VFIO
> select HAVE_KVM_IRQ_BYPASS
>
> diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
> index c50328212917..77379f77840a 100644
> --- a/arch/riscv/kvm/Kconfig
> +++ b/arch/riscv/kvm/Kconfig
> @@ -23,7 +23,6 @@ config KVM
> select HAVE_KVM_IRQCHIP
> select HAVE_KVM_IRQ_ROUTING
> select HAVE_KVM_MSI
> - select HAVE_KVM_VCPU_ASYNC_IOCTL
> select HAVE_KVM_READONLY_MEM
> select HAVE_KVM_DIRTY_RING_ACQ_REL
> select KVM_COMMON
> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> index cae908d64550..96d16028e8b7 100644
> --- a/arch/s390/kvm/Kconfig
> +++ b/arch/s390/kvm/Kconfig
> @@ -20,7 +20,6 @@ config KVM
> def_tristate y
> prompt "Kernel-based Virtual Machine (KVM) support"
> select HAVE_KVM_CPU_RELAX_INTERCEPT
> - select HAVE_KVM_VCPU_ASYNC_IOCTL
> select KVM_ASYNC_PF
> select KVM_ASYNC_PF_SYNC
> select KVM_COMMON
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b4b5d2d09634..ca5ba2caf314 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7240,6 +7240,12 @@ static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp)
> return 0;
> }
>
> +long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl,
> + unsigned long arg)
> +{
> + return -ENOIOCTLCMD;
> +}
> +
> int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> {
> struct kvm *kvm = filp->private_data;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 5bd76cf394fa..7186b2ae4b57 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2437,18 +2437,8 @@ static inline bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
> }
> #endif /* CONFIG_HAVE_KVM_NO_POLL */
>
> -#ifdef CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL
> long kvm_arch_vcpu_async_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg);
> -#else
> -static inline long kvm_arch_vcpu_async_ioctl(struct file *filp,
> - unsigned int ioctl,
> - unsigned long arg)
> -{
> - return -ENOIOCTLCMD;
> -}
> -#endif /* CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL */
> -
> void kvm_arch_guest_memory_reclaimed(struct kvm *kvm);
>
> #ifdef CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index 5f0015c5dd95..267c7369c765 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -78,9 +78,6 @@ config HAVE_KVM_IRQ_BYPASS
> tristate
> select IRQ_BYPASS_MANAGER
>
> -config HAVE_KVM_VCPU_ASYNC_IOCTL
> - bool
> -
> config HAVE_KVM_VCPU_RUN_PID_CHANGE
> bool
>
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