linux-kernel - Re: [PATCH] KVM: irqchip: synchronize srcu only if needed

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Message-ID: <CAN35MuRKMW+-qrf0Sv-tsiZ71_-C_DJAMhu=HhtP8RnTVW-PsA@mail.gmail.com>
Date: Wed, 17 Jan 2024 08:56:49 +0800
From: Yi Wang <up2wing@...il.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>, pbonzini@...hat.com, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org, 
	hpa@...or.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	wanpengli@...cent.com, Yi Wang <foxywang@...cent.com>, 
	Oliver Upton <oliver.upton@...ux.dev>, Marc Zyngier <maz@...nel.org>, 
	Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>
Subject: Re: [PATCH] KVM: irqchip: synchronize srcu only if needed

On Wed, Jan 17, 2024 at 12:58 AM Sean Christopherson <seanjc@...glecom> wrote:
>
> On Tue, Jan 16, 2024, Christian Borntraeger wrote:
> >
> >

...

> >
> > I would be fine with wasted memory.
>
> +1.  If we really, really want to avoid the negligible memory overhead, we could
> pre-configure a static global table and directly use that as the dummy table (and
> exempt it from being freed by free_irq_routing_table()).

Thanks for the suggestion! Well, in my opinion it may be better to fix
the current issue
and I'm glad to send another patch to optimize this.

> > The only question is does it have a functional impact or can we simply ignore
> > the dummy routing.
>
> Given the lack of sanity checks on kvm->irq_routing, I'm pretty sure the only way
> for there to be functional impact is if there's a latent NULL pointer deref hiding
> somewhere.


-- 
---
Best wishes
Yi Wang