linux-kernel - Re: [patch 6/7] genirq: Provide interrupt injection mechanism

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Date:   Fri, 06 Mar 2020 13:52:10 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        Keith Busch <kbusch@...nel.org>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: Re: [patch 6/7] genirq: Provide interrupt injection mechanism

On 2020-03-06 13:03, Thomas Gleixner wrote:
> Error injection mechanisms need a half ways safe way to inject 
> interrupts as
> invoking generic_handle_irq() or the actual device interrupt handler
> directly from e.g. a debugfs write is not guaranteed to be safe.
> 
> On x86 generic_handle_irq() is unsafe due to the hardware trainwreck 
> which
> is the base of x86 interrupt delivery and affinity management.
> 
> Move the irq debugfs injection code into a separate function which can 
> be
> used by error injection code as well.
> 
> The implementation prevents at least that state is corrupted, but it 
> cannot
> close a very tiny race window on x86 which might result in a stale and 
> not
> serviced device interrupt under very unlikely circumstances.
> 
> This is explicitly for debugging and testing and not for production use 
> or
> abuse in random driver code.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Acked-by: Marc Zyngier <maz@...nel.org>

         M.
-- 
Jazz is not dead. It just smells funny...