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Date: Wed, 29 Apr 2020 19:31:21 +0300
From: "Paraschiv, Andra-Irina" <andraprs@...zon.com>
To: Liran Alon <liran.alon@...cle.com>, <linux-kernel@...r.kernel.org>
CC: Anthony Liguori <aliguori@...zon.com>,
Benjamin Herrenschmidt <benh@...zon.com>,
Colm MacCarthaigh <colmmacc@...zon.com>,
Bjoern Doebel <doebel@...zon.de>,
David Woodhouse <dwmw@...zon.co.uk>,
Frank van der Linden <fllinden@...zon.com>,
Alexander Graf <graf@...zon.de>,
Martin Pohlack <mpohlack@...zon.de>,
Matt Wilson <msw@...zon.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Balbir Singh <sblbir@...zon.com>,
Stewart Smith <trawets@...zon.com>,
Uwe Dannowski <uwed@...zon.de>, <kvm@...r.kernel.org>,
<ne-devel-upstream@...zon.com>
Subject: Re: [PATCH v1 04/15] nitro_enclaves: Init PCI device driver
On 25/04/2020 17:25, Liran Alon wrote:
>
> On 21/04/2020 21:41, Andra Paraschiv wrote:
>> +
>> +/**
>> + * ne_setup_msix - Setup MSI-X vectors for the PCI device.
>> + *
>> + * @pdev: PCI device to setup the MSI-X for.
>> + * @ne_pci_dev: PCI device private data structure.
>> + *
>> + * @returns: 0 on success, negative return value on failure.
>> + */
>> +static int ne_setup_msix(struct pci_dev *pdev, struct ne_pci_dev
>> *ne_pci_dev)
>> +{
>> + int nr_vecs = 0;
>> + int rc = -EINVAL;
>> +
>> + BUG_ON(!ne_pci_dev);
> This kind of defensive programming does not align with Linux coding
> convention.
> I think these BUG_ON() conditions should be removed.
I replaced with WARN_ON here and in the other places in the codebase.
>> +
>> + nr_vecs = pci_msix_vec_count(pdev);
>> + if (nr_vecs < 0) {
>> + rc = nr_vecs;
>> +
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in getting vec count [rc=%d]\n",
>> + rc);
>> +
>> + return rc;
>> + }
>> +
>> + rc = pci_alloc_irq_vectors(pdev, nr_vecs, nr_vecs, PCI_IRQ_MSIX);
>> + if (rc < 0) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in alloc MSI-X vecs [rc=%d]\n",
>> + rc);
>> +
>> + goto err_alloc_irq_vecs;
> You should just replace this with "return rc;" as no cleanup is
> required here.
Done.
>> + }
>> +
>> + return 0;
>> +
>> +err_alloc_irq_vecs:
>> + return rc;
>> +}
>> +
>> +/**
>> + * ne_pci_dev_enable - Select PCI device version and enable it.
>> + *
>> + * @pdev: PCI device to select version for and then enable.
>> + * @ne_pci_dev: PCI device private data structure.
>> + *
>> + * @returns: 0 on success, negative return value on failure.
>> + */
>> +static int ne_pci_dev_enable(struct pci_dev *pdev,
>> + struct ne_pci_dev *ne_pci_dev)
>> +{
>> + u8 dev_enable_reply = 0;
>> + u16 dev_version_reply = 0;
>> +
>> + BUG_ON(!pdev);
>> + BUG_ON(!ne_pci_dev);
>> + BUG_ON(!ne_pci_dev->iomem_base);
> Same.
>> +
>> + iowrite16(NE_VERSION_MAX, ne_pci_dev->iomem_base + NE_VERSION);
>> +
>> + dev_version_reply = ioread16(ne_pci_dev->iomem_base + NE_VERSION);
>> + if (dev_version_reply != NE_VERSION_MAX) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in pci dev version cmd\n");
>> +
>> + return -EIO;
>> + }
>> +
>> + iowrite8(NE_ENABLE_ON, ne_pci_dev->iomem_base + NE_ENABLE);
>> +
>> + dev_enable_reply = ioread8(ne_pci_dev->iomem_base + NE_ENABLE);
>> + if (dev_enable_reply != NE_ENABLE_ON) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in pci dev enable cmd\n");
>> +
>> + return -EIO;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * ne_pci_dev_disable - Disable PCI device.
>> + *
>> + * @pdev: PCI device to disable.
>> + * @ne_pci_dev: PCI device private data structure.
>> + *
>> + * @returns: 0 on success, negative return value on failure.
>> + */
>> +static int ne_pci_dev_disable(struct pci_dev *pdev,
>> + struct ne_pci_dev *ne_pci_dev)
>> +{
>> + u8 dev_disable_reply = 0;
>> +
>> + BUG_ON(!pdev);
>> + BUG_ON(!ne_pci_dev);
>> + BUG_ON(!ne_pci_dev->iomem_base);
> Same.
>> +
>> + iowrite8(NE_ENABLE_OFF, ne_pci_dev->iomem_base + NE_ENABLE);
>> +
>> + /*
>> + * TODO: Check for NE_ENABLE_OFF in a loop, to handle cases when
>> the
>> + * device state is not immediately set to disabled and going
>> through a
>> + * transitory state of disabling.
>> + */
>> + dev_disable_reply = ioread8(ne_pci_dev->iomem_base + NE_ENABLE);
>> + if (dev_disable_reply != NE_ENABLE_OFF) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in pci dev disable cmd\n");
>> +
>> + return -EIO;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int ne_probe(struct pci_dev *pdev, const struct pci_device_id
>> *id)
>> +{
>> + struct ne_pci_dev *ne_pci_dev = NULL;
>> + int rc = -EINVAL;
> Unnecessary variable initialization.
> ne_pci_dev and rc are initialized below always before they are used.
I would rather keep the initialization in place overall, to not have a
mix of init and uninit vars, when needed.
>> +
>> + ne_pci_dev = kzalloc(sizeof(*ne_pci_dev), GFP_KERNEL);
>> + if (!ne_pci_dev)
>> + return -ENOMEM;
>> +
>> + rc = pci_enable_device(pdev);
>> + if (rc < 0) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in pci dev enable [rc=%d]\n", rc);
>> +
> Why is this dev_err_ratelimited() instead of dev_err()?
> Same for the rest of error printing in this probe() method and other
> places in this patch.
Just to avoid any misbehaving scenario, where would be way too many logs
in a short timeframe. Here may not happen, but while handling PCI dev
requests could be.
>> + goto err_pci_enable_dev;
> I find it confusing that the error labels are named based on the
> failure-case they are used,
> instead of the action they do (i.e. Unwind previous successful
> operation that requires unwinding).
> This doesn't seem to match Linux kernel coding convention.
> It also created an unnecessary 2 labels pointing to the same place in
> cleanup code.
Yep, that's better this way wrt the naming of the labels. I updated the
gotos in the patch series.
>> + }
>> +
>> + rc = pci_request_regions_exclusive(pdev, "ne_pci_dev");
>> + if (rc < 0) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in pci request regions [rc=%d]\n",
>> + rc);
>> +
>> + goto err_req_regions;
>> + }
>> +
>> + ne_pci_dev->iomem_base = pci_iomap(pdev, PCI_BAR_NE, 0);
>> + if (!ne_pci_dev->iomem_base) {
>> + rc = -ENOMEM;
>> +
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in pci bar mapping [rc=%d]\n", rc);
>> +
>> + goto err_iomap;
>> + }
>> +
>> + rc = ne_setup_msix(pdev, ne_pci_dev);
>> + if (rc < 0) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in pci dev msix setup [rc=%d]\n",
>> + rc);
>> +
>> + goto err_setup_msix;
>> + }
>> +
>> + rc = ne_pci_dev_disable(pdev, ne_pci_dev);
>> + if (rc < 0) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in ne_pci_dev disable [rc=%d]\n",
>> + rc);
>> +
>> + goto err_ne_pci_dev_disable;
>> + }
> It seems weird that we need to disable the device before enabling it
> on the probe() method.
> Why can't we just enable the device without disabling it?
The pci dev disable call cleanups the internal state of the device and
terminates any running / "dangling" enclaves; here it is included just
in case any remaining state from a previous PCI device use. The below
enable call would fail in that case, though.
>> +
>> + rc = ne_pci_dev_enable(pdev, ne_pci_dev);
>> + if (rc < 0) {
>> + dev_err_ratelimited(&pdev->dev,
>> + "Failure in ne_pci_dev enable [rc=%d]\n",
>> + rc);
>> +
>> + goto err_ne_pci_dev_enable;
>> + }
>> +
>> + atomic_set(&ne_pci_dev->cmd_reply_avail, 0);
>> + init_waitqueue_head(&ne_pci_dev->cmd_reply_wait_q);
>> + INIT_LIST_HEAD(&ne_pci_dev->enclaves_list);
>> + mutex_init(&ne_pci_dev->enclaves_list_mutex);
>> + mutex_init(&ne_pci_dev->pci_dev_mutex);
>> +
>> + pci_set_drvdata(pdev, ne_pci_dev);
> If you would have pci_set_drvdata() as one of the first operations in
> ne_probe(), then you could have avoided
> passing both struct pci_dev and struct ne_pci_dev parameters to
> ne_setup_msix(), ne_pci_dev_enable() and ne_pci_dev_disable().
> Which would have been a bit more elegant.
Fair point. I moved pci_set_drvdata() upper in the logic and updated the
signature of the functions to only include the pci_dev parameter.
>> +
>> + return 0;
>> +
>> +err_ne_pci_dev_enable:
>> +err_ne_pci_dev_disable:
>> + pci_free_irq_vectors(pdev);
>> +err_setup_msix:
>> + pci_iounmap(pdev, ne_pci_dev->iomem_base);
>> +err_iomap:
>> + pci_release_regions(pdev);
>> +err_req_regions:
>> + pci_disable_device(pdev);
>> +err_pci_enable_dev:
>> + kzfree(ne_pci_dev);
> An empty new-line is appropriate here.
> To separate the return statement from the cleanup logic.
Done.
>> + return rc;
>> +}
>> +
>> +static void ne_remove(struct pci_dev *pdev)
>> +{
>> + struct ne_pci_dev *ne_pci_dev = pci_get_drvdata(pdev);
>> +
>> + if (!ne_pci_dev || !ne_pci_dev->iomem_base)
>> + return;
> Why is this condition necessary?
> The ne_remove() function should be called only in case ne_probe()
> succeeded.
> In that case, both ne_pci_dev and ne_pci_dev->iomem_base should be
> non-NULL.
Correct, that shouldn't happen.
Just for early exit in case of bad behavior.
>> +
>> + ne_pci_dev_disable(pdev, ne_pci_dev);
>> +
>> + pci_set_drvdata(pdev, NULL);
>> +
>> + pci_free_irq_vectors(pdev);
>> +
>> + pci_iounmap(pdev, ne_pci_dev->iomem_base);
>> +
>> + kzfree(ne_pci_dev);
>> +
>> + pci_release_regions(pdev);
>> +
>> + pci_disable_device(pdev);
> You should aspire to keep ne_remove() order of operations to be the
> reverse order of operations done in ne_probe().
> Which would also nicely match the order of operations done in
> ne_probe() cleanup.
> i.e. The following order:
>
> pci_set_drvdata();
> ne_pci_dev_disable();
> pci_free_irq_vectors();
> pci_iounmap();
> pci_release_regions();
> pci_disable_device()
> kzfree();
I updated the order of operations.
Thanks for review, Liran.
Andra
Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.
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