linux-kernel - Re: [PATCH v4 07/18] nitro_enclaves: Init misc device providing the ioctl interface

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Date:   Mon, 6 Jul 2020 10:01:42 +0200
From:   Alexander Graf <graf@...zon.de>
To:     "Paraschiv, Andra-Irina" <andraprs@...zon.com>,
        <linux-kernel@...r.kernel.org>
CC:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Colm MacCarthaigh <colmmacc@...zon.com>,
        Bjoern Doebel <doebel@...zon.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Frank van der Linden <fllinden@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Martin Pohlack <mpohlack@...zon.de>,
        "Matt Wilson" <msw@...zon.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Balbir Singh <sblbir@...zon.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        "Stefan Hajnoczi" <stefanha@...hat.com>,
        Stewart Smith <trawets@...zon.com>,
        "Uwe Dannowski" <uwed@...zon.de>, <kvm@...r.kernel.org>,
        <ne-devel-upstream@...zon.com>
Subject: Re: [PATCH v4 07/18] nitro_enclaves: Init misc device providing the
 ioctl interface



On 06.07.20 09:49, Paraschiv, Andra-Irina wrote:
> 
> 
> On 06/07/2020 10:13, Alexander Graf wrote:
>>
>>
>> On 22.06.20 22:03, Andra Paraschiv wrote:
>>> The Nitro Enclaves driver provides an ioctl interface to the user space
>>> for enclave lifetime management e.g. enclave creation / termination and
>>> setting enclave resources such as memory and CPU.
>>>
>>> This ioctl interface is mapped to a Nitro Enclaves misc device.
>>>
>>> Signed-off-by: Andra Paraschiv <andraprs@...zon.com>
>>> ---
>>> Changelog
>>>
>>> v3 -> v4
>>>
>>> * Use dev_err instead of custom NE log pattern.
>>> * Remove the NE CPU pool init during kernel module loading, as the CPU
>>>    pool is now setup at runtime, via a sysfs file for the kernel
>>>    parameter.
>>> * Add minimum enclave memory size definition.
>>>
>>> v2 -> v3
>>>
>>> * Remove the GPL additional wording as SPDX-License-Identifier is
>>>    already in place.
>>> * Remove the WARN_ON calls.
>>> * Remove linux/bug and linux/kvm_host includes that are not needed.
>>> * Remove "ratelimited" from the logs that are not in the ioctl call
>>>    paths.
>>> * Remove file ops that do nothing for now - open and release.
>>>
>>> v1 -> v2
>>>
>>> * Add log pattern for NE.
>>> * Update goto labels to match their purpose.
>>> * Update ne_cpu_pool data structure to include the global mutex.
>>> * Update NE misc device mode to 0660.
>>> * Check if the CPU siblings are included in the NE CPU pool, as full CPU
>>>    cores are given for the enclave(s).
>>> ---
>>>   drivers/virt/nitro_enclaves/ne_misc_dev.c | 133 ++++++++++++++++++++++
>>>   drivers/virt/nitro_enclaves/ne_pci_dev.c  |  11 ++
>>>   2 files changed, 144 insertions(+)
>>>   create mode 100644 drivers/virt/nitro_enclaves/ne_misc_dev.c
>>>
>>> diff --git a/drivers/virt/nitro_enclaves/ne_misc_dev.c 
>>> b/drivers/virt/nitro_enclaves/ne_misc_dev.c
>>> new file mode 100644
>>> index 000000000000..628fb10c2b36
>>> --- /dev/null
>>> +++ b/drivers/virt/nitro_enclaves/ne_misc_dev.c
>>> @@ -0,0 +1,133 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights 
>>> Reserved.
>>> + */
>>> +
>>> +/**
>>> + * Enclave lifetime management driver for Nitro Enclaves (NE).
>>> + * Nitro is a hypervisor that has been developed by Amazon.
>>> + */
>>> +
>>> +#include <linux/anon_inodes.h>
>>> +#include <linux/capability.h>
>>> +#include <linux/cpu.h>
>>> +#include <linux/device.h>
>>> +#include <linux/file.h>
>>> +#include <linux/hugetlb.h>
>>> +#include <linux/list.h>
>>> +#include <linux/miscdevice.h>
>>> +#include <linux/mm.h>
>>> +#include <linux/mman.h>
>>> +#include <linux/module.h>
>>> +#include <linux/mutex.h>
>>> +#include <linux/nitro_enclaves.h>
>>> +#include <linux/pci.h>
>>> +#include <linux/poll.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/types.h>
>>> +
>>> +#include "ne_misc_dev.h"
>>> +#include "ne_pci_dev.h"
>>> +
>>> +#define NE_EIF_LOAD_OFFSET (8 * 1024UL * 1024UL)
>>> +
>>> +#define NE_MIN_ENCLAVE_MEM_SIZE (64 * 1024UL * 1024UL)
>>> +
>>> +#define NE_MIN_MEM_REGION_SIZE (2 * 1024UL * 1024UL)
>>> +
>>> +/*
>>> + * TODO: Update logic to create new sysfs entries instead of using
>>> + * a kernel parameter e.g. if multiple sysfs files needed.
>>> + */
>>> +static const struct kernel_param_ops ne_cpu_pool_ops = {
>>
>> Adding an empty ops struct looks very odd. If you fill it in a later 
>> patch, please indicate so in a comment here.
> 
> True, I already updated this in v5, to have the .get function here and 
> the .set one in a later patch.
> 
>>
>>> +};
>>> +
>>> +static char ne_cpus[PAGE_SIZE];
>>
>> PAGE_SIZE is a bit excessive, no? Even if you list every single CPU of 
>> a 256 CPU system you are <1024.
> 
> It is a bit too much, I was thinking of it while declaring this. I can 
> update to 1024 in v5.

The largest NUMA node CPU count I'm aware of today is 64. Since we limit 
the pool to a single node, we can't go beyond that. Let's be a bit 
future proof and double that number: 128. Then we get to 401 characters 
if you pass in every single CPU as comma separated. I would seriously 
hope most people would just pass ranges though.

So how about we make it 512 for now?


Thanks,

Alex



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