linux-kernel - KVM exit to userspace on WFI

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Message-ID: <CANi1PHhzk80HvwQbBM46gpJ6_AA_P6+m5Jo0Nuy_MAdA4C2BhQ@mail.gmail.com>
Date:   Fri, 20 Oct 2023 20:45:05 +0200
From:   Jan Henrik Weinstock <jan@....re>
To:     maz@...nel.org, oliver.upton@...ux.dev, james.morse@....com,
        suzuki.poulose@....com, yuzenghui@...wei.com,
        catalin.marinas@....com, will@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Lukas Jünger <lukas@....re>
Subject: KVM exit to userspace on WFI

Hi all,

I am looking for a way to have KVM_RUN exit back to userspace once the
vcpu encounters a WFI. It seems the kvm_run->request_interrupt_window
flag is currently ignored by arm64. So my solution thus far is to
patch kvm_handle_wfx in arch/arm64/kvm/handle_exit.c and return to
userspace with KVM_EXIT_IRQ_WINDOW_OPEN - working example attached.
Any chance to get this (or something similar) mainline?

-- 
Dr.-Ing. Jan Henrik Weinstock
Managing Director

MachineWare GmbH | www.machineware.de
Hühnermarkt 19, 52062 Aachen, Germany
Amtsgericht Aachen HRB25734

Geschäftsführung
Lukas Jünger
Dr.-Ing. Jan Henrik Weinstock

View attachment "kvm.patch" of type "text/x-patch" (1339 bytes)