linux-kernel - Re: [PATCH v8 2/2] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node

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Date:   Sat, 23 Oct 2021 08:33:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        reinette.chatre@...el.com, tony.luck@...el.com,
        linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org
Subject: Re: [PATCH v8 2/2] x86/sgx: Add an attribute for the amount of SGX
 memory in a NUMA node

On Sat, Oct 23, 2021 at 04:02:48AM +0300, Jarkko Sakkinen wrote:
> On Mon, 2021-10-18 at 16:35 +0200, Greg Kroah-Hartman wrote:
> > > +               ret = sysfs_create_group(&dev->kobj, &sgx_node_attr_group);
> > 
> > A huge hint, if a driver has to call a sysfs_* call, something is wrong.
> > 
> > Something is wrong here.
> > 
> > Why are you messing around with a kobject?  This is a device, that you
> > control, you can just set the default attribute group for it and then
> > the driver core will add and remove the sysfs group at the proper time,
> > in the proper way.  Right now you are racing userspace and loosing.
> > 
> > Use the default group list, that is what it is there for.
> 
> I used sysfs_create_group() because node_devices is not owned by SGX
> code. It is managed in drivers/base/node.c, and also initialized before
> SGX.

Then that is broken, please do not use that device as your code does not
"own" it.  Or fix the logic to be initialized earlier.

thanks,

greg k-h