linux-kernel - Re: [PATCH v2] KVM: x86: Check irqchip mode before create PIT

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Date: Fri, 26 Jan 2024 19:12:24 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Tengfei Yu <moehanabichan@...il.com>
Cc: Sean Christopherson <seanjc@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: x86: Check irqchip mode before create PIT

On Thu, Jan 25, 2024 at 6:09 AM Tengfei Yu <moehanabichan@...il.com> wrote:
>
> As the kvm api(https://docs.kernel.org/virt/kvm/api.html) reads,
> KVM_CREATE_PIT2 call is only valid after enabling in-kernel irqchip
> support via KVM_CREATE_IRQCHIP.
>
> Without this check, I can create PIT first and enable irqchip-split
> then, which may cause the PIT invalid because of lacking of in-kernel
> PIC to inject the interrupt.
>
> Signed-off-by: Tengfei Yu <moehanabichan@...il.com>

Queued, thanks.

Paolo

> ---
> v1 -> v2: Change errno from -EEXIST to -ENOENT.
> v1 link: https://lore.kernel.org/lkml/ZbGkZlFmi1war6vq@google.com/
>
>  arch/x86/kvm/x86.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 27e23714e960..c1e3aecd627f 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7016,6 +7016,9 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
>                 r = -EEXIST;
>                 if (kvm->arch.vpit)
>                         goto create_pit_unlock;
> +               r = -ENOENT;
> +               if (!pic_in_kernel(kvm))
> +                       goto create_pit_unlock;
>                 r = -ENOMEM;
>                 kvm->arch.vpit = kvm_create_pit(kvm, u.pit_config.flags);
>                 if (kvm->arch.vpit)
> --
> 2.39.3
>