linux-kernel - Re: [RFC PATCH v3 0/5] x86/kvm: Virtual suspend time injection support

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Message-ID: <874k9bdcrk.wl-maz@kernel.org>
Date:   Wed, 20 Oct 2021 14:52:31 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Hikaru Nishida <hikalium@...omium.org>
Cc:     linux-kernel@...r.kernel.org, dme@....org, tglx@...utronix.de,
        mlevitsk@...hat.com, linux@...ck-us.net, pbonzini@...hat.com,
        vkuznets@...hat.com, will@...nel.org, suleiman@...gle.com,
        senozhatsky@...gle.com, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        John Stultz <john.stultz@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, x86@...nel.org
Subject: Re: [RFC PATCH v3 0/5] x86/kvm: Virtual suspend time injection support

Hi Hikaru,

On Wed, 20 Oct 2021 13:04:25 +0100,
Hikaru Nishida <hikalium@...omium.org> wrote:
> 
> 
> Hi,
> 
> This patch series adds virtual suspend time injection support to KVM.
> It is an updated version of the following series:
> v2:
> https://lore.kernel.org/kvm/20210806100710.2425336-1-hikalium@chromium.org/
> v1:
> https://lore.kernel.org/kvm/20210426090644.2218834-1-hikalium@chromium.org/
> 
> Please take a look again.
> 
> To kvm/arm64 folks:
> I'm going to implement this mechanism to ARM64 as well but not
> sure which function should be used to make an IRQ (like kvm_apic_set_irq
> in x86) and if it is okay to use kvm_gfn_to_hva_cache /
> kvm_write_guest_cached for sharing the suspend duration.

Before we discuss interrupt injection, I want to understand what this
is doing, and how this is doing it. And more precisely, I want to find
out how you solve the various problems described by Thomas here [1].

Assuming you solve these, you should model the guest memory access
similarly to what we do for stolen time. As for injecting an
interrupt, why can't this be a userspace thing?

Thanks,

	M.

[1] https://lore.kernel.org/all/871r557jls.ffs@tglx


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