linux-kernel - Re: [RESEND PATCH 4/6] x86/traps: add external_interrupt() to dispatch external interrupts

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Message-ID: <Y20lyBl67GDZVOeB@google.com>
Date:   Thu, 10 Nov 2022 16:24:40 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Xin Li <xin3.li@...el.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, pbonzini@...hat.com,
        kevin.tian@...el.com
Subject: Re: [RESEND PATCH 4/6] x86/traps: add external_interrupt() to
 dispatch external interrupts

On Wed, Nov 09, 2022, Xin Li wrote:
> +__visible noinstr void external_interrupt(struct pt_regs *regs,
> +					  unsigned int vector)
> +{
> +	unsigned int sysvec = vector - FIRST_SYSTEM_VECTOR;
> +
> +	BUG_ON(vector < FIRST_EXTERNAL_VECTOR);

Why not return an error up the stack?  KVM and/or CPU bugs aren't unheard of.
Dropping an IRQ obviously isn't ideal, but there's a non-zero chance that letting
KVM WARN and kill the VM will keep the host alive and thus other VMs running.  A
somewhat sophisticated setup might even react to the VM being killed by migrating
other VMs off the system and initiating host maintenance.