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From: Matthew Rosato <mjrosato@linux.ibm.com>
To: Eric Farman <farman@linux.ibm.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Halil Pasic <pasic@linux.ibm.com>
Cc: Jared Rossi <jrossi@linux.ibm.com>,
	linux-s390@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v6 1/3] vfio-ccw: Check initialized flag in cp_init()
Date: Tue, 11 May 2021 16:10:21 -0400	[thread overview]
Message-ID: <927149fb-ec36-ccfa-84ac-0b10ac472f84@linux.ibm.com> (raw)
In-Reply-To: <20210511195631.3995081-2-farman@linux.ibm.com>

On 5/11/21 3:56 PM, Eric Farman wrote:
> We have a really nice flag in the channel_program struct that
> indicates if it had been initialized by cp_init(), and use it
> as a guard in the other cp accessor routines, but not for a
> duplicate call into cp_init(). The possibility of this occurring
> is low, because that flow is protected by the private->io_mutex
> and FSM CP_PROCESSING state. But then why bother checking it
> in (for example) cp_prefetch() then?
> 
> Let's just be consistent and check for that in cp_init() too.
> 
> Fixes: 71189f263f8a3 ("vfio-ccw: make it safe to access channel programs")
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Acked-by: Matthew Rosato <mjrosato@linux.ibm.com>

> ---
>   drivers/s390/cio/vfio_ccw_cp.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> index b9febc581b1f..8d1b2771c1aa 100644
> --- a/drivers/s390/cio/vfio_ccw_cp.c
> +++ b/drivers/s390/cio/vfio_ccw_cp.c
> @@ -638,6 +638,10 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
>   	static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 1);
>   	int ret;
>   
> +	/* this is an error in the caller */
> +	if (cp->initialized)
> +		return -EBUSY;
> +
>   	/*
>   	 * We only support prefetching the channel program. We assume all channel
>   	 * programs executed by supported guests likewise support prefetching.
> 


  reply	other threads:[~2021-05-11 20:10 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-11 19:56 [PATCH v6 0/3] vfio-ccw: Fix interrupt handling for HALT/CLEAR Eric Farman
2021-05-11 19:56 ` [PATCH v6 1/3] vfio-ccw: Check initialized flag in cp_init() Eric Farman
2021-05-11 20:10   ` Matthew Rosato [this message]
2021-05-11 19:56 ` [PATCH v6 2/3] vfio-ccw: Reset FSM state to IDLE inside FSM Eric Farman
2021-05-11 20:38   ` Matthew Rosato
2021-05-11 19:56 ` [PATCH v6 3/3] vfio-ccw: Serialize FSM IDLE state with I/O completion Eric Farman
2021-05-11 20:45   ` Matthew Rosato
2021-05-12 10:49   ` Cornelia Huck
2021-05-13  1:05 ` [PATCH v6 0/3] vfio-ccw: Fix interrupt handling for HALT/CLEAR Halil Pasic
2021-05-13 18:33   ` Eric Farman
2021-05-14  0:29     ` Halil Pasic
2021-05-18  9:49 ` Cornelia Huck

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