linux-kernel - Re: Enabling interrupts in QEMU TPM TIS

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Message-ID: <20200625172802.GS6578@ziepe.ca>
Date:   Thu, 25 Jun 2020 14:28:02 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Stefan Berger <stefanb@...ux.ibm.com>
Cc:     Jerry Snitselaar <jsnitsel@...hat.com>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Enabling interrupts in QEMU TPM TIS

On Thu, Jun 25, 2020 at 10:56:43AM -0400, Stefan Berger wrote:
> Hello!
> 
>  I want to enable IRQs now in QEMU's TPM TIS device model and I need to work
> with the following patch to Linux TIS. I am wondering whether the changes
> there look reasonable to you? Windows works with the QEMU modifications
> as-is, so maybe it's a bug in the TIS code (which I had not run into
> before).
> 
> 
> The point of the loop I need to introduce in the interrupt handler is that
> while the interrupt handler is running another interrupt may occur/be posted
> that then does NOT cause the interrupt handler to be invoked again but
> causes a stall, unless the loop is there.

That seems like a qemu bug, TPM interrupts are supposed to be level
interrupts, not edge.

Jason