Re: [PATCH 1/2] x86/kvm/vmx: Move IRQ/NMI dispatch from KVM into x86 core

[Xin Li]

Few nits below, but

Reviewed-by: Xin Li <xin@xxxxxxxxx <mailto:xin@xxxxxxxxx>>


> On Apr 23, 2026, at 8:56 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> Move the VMX interrupt dispatch magic into the x86 core code. This
> isolates KVM from the FRED/IDT decisions and reduces the amount of
> EXPORT_SYMBOL_FOR_KVM().
> 
> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Tested-by: "Verma, Vishal L" <vishal.l.verma@xxxxxxxxx>
> --- /dev/null
> +++ b/arch/x86/entry/common.c
> @@ -0,0 +1,48 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <linux/entry-common.h>
> +#include <linux/kvm_types.h>
> +#include <asm/fred.h>
> +#include <asm/desc.h>

Swap the two header inclusion order?

> +
> +#if IS_ENABLED(CONFIG_KVM_INTEL)
> +/*
> + * On VMX, NMIs and IRQs (as configured by KVM) are acknowledge by hardware as
> + * part of the VM-Exit, i.e. the event itself is consumed as part the VM-Exit.
> + * x86_entry_from_kvm() is invoked by KVM to effectively forward NMIs and IRQs
> + * to the kernel for servicing.  On SVM, a.k.a. AMD, the NMI/IRQ VM-Exit is
> + * purely a signal that an NMI/IRQ is pending, i.e. the event that triggered
> + * the VM-Exit is held pending until it's unblocked in the host.
> + */
> +noinstr void x86_entry_from_kvm(unsigned int event_type, unsigned int vector)

Is u32 better than unsigned int as is close to hardware definition?

Currently, the event type and event vector are defined as 4-bit and 8-bit
fields, respectively; and they can be readily expanded to 8 and 16 bits by
utilizing adjacent reserved bits.

> +{
> + if (event_type == EVENT_TYPE_EXTINT) {
> +#ifdef CONFIG_X86_64
> + /*
> + * Use FRED dispatch, even when running IDT. The dispatch
> + * tables are kept in sync between FRED and IDT, and the FRED
> + * dispatch works well with CFI.
> + */
> + fred_entry_from_kvm(event_type, vector);

Then should we rename the “fred_” prefix, say “x86_64_"?

Sorry naming is hard to me ;)