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

From: Marc Zyngier <maz@kernel.org>
To: Hikaru Nishida <hikalium@chromium.org>
Cc: linux-kernel@vger.kernel.org, dme@dme.org, tglx@linutronix.de,
	mlevitsk@redhat.com, linux@roeck-us.net, pbonzini@redhat.com,
	vkuznets@redhat.com, will@kernel.org, suleiman@google.com,
	senozhatsky@google.com, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org,
	Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Jim Mattson <jmattson@google.com>,
	Joerg Roedel <joro@8bytes.org>,
	John Stultz <john.stultz@linaro.org>,
	Jonathan Corbet <corbet@lwn.net>, Juergen Gross <jgross@suse.com>,
	Kees Cook <keescook@chromium.org>,
	Lai Jiangshan <laijs@linux.alibaba.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Sean Christopherson <seanjc@google.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Wanpeng Li <wanpengli@tencent.com>,
	kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org
Subject: Re: [RFC PATCH v3 0/5] x86/kvm: Virtual suspend time injection support
Date: Wed, 20 Oct 2021 14:52:31 +0100	[thread overview]
Message-ID: <874k9bdcrk.wl-maz@kernel.org> (raw)
In-Reply-To: <20211020120431.776494-1-hikalium@chromium.org>

Hi Hikaru,

On Wed, 20 Oct 2021 13:04:25 +0100,
Hikaru Nishida <hikalium@chromium.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

-- 
Without deviation from the norm, progress is not possible.

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