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Date: Wed, 15 Jul 2015 15:59:44 -0500
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Sreekanth Reddy <sreekanth.reddy@...gotech.com>
Cc: tpearson@...torengineeringinc.com, jejb@...nel.org,
martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
JBottomley@...allels.com, Sathya.Prakash@...gotech.com,
linux-kernel@...r.kernel.org, hch@...radead.org
Subject: Re: [PATCH v3] [SCSI] mpt2sas, mpt3sas: Abort initialization if no
memory I/O resources detected
On Wed, Jul 15, 2015 at 10:19:56AM +0530, Sreekanth Reddy wrote:
> Driver crashes if the BIOS do not set up at least one
> memory I/O resource. This failure can happen if the device is too
> slow to respond during POST and is missed by the BIOS, but Linux
> then detects the device later in the boot process.
>
> Changes in v3:
> Rearranged the code to remove the code redundancy
>
> Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@...gotech.com>
> ---
> drivers/scsi/mpt2sas/mpt2sas_base.c | 16 +++++++++-------
> drivers/scsi/mpt3sas/mpt3sas_base.c | 16 +++++++++-------
> 2 files changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
> index 11248de..6dec7cf 100644
> --- a/drivers/scsi/mpt2sas/mpt2sas_base.c
> +++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
> @@ -1557,7 +1557,8 @@ mpt2sas_base_map_resources(struct MPT2SAS_ADAPTER *ioc)
> goto out_fail;
> }
>
> - for (i = 0, memap_sz = 0, pio_sz = 0 ; i < DEVICE_COUNT_RESOURCE; i++) {
> + for (i = 0, memap_sz = 0, pio_sz = 0; (i < DEVICE_COUNT_RESOURCE) &&
> + (!memap_sz || !pio_sz); i++) {
> if (pci_resource_flags(pdev, i) & IORESOURCE_IO) {
> if (pio_sz)
> continue;
> @@ -1572,16 +1573,17 @@ mpt2sas_base_map_resources(struct MPT2SAS_ADAPTER *ioc)
> chip_phys = (u64)ioc->chip_phys;
> memap_sz = pci_resource_len(pdev, i);
> ioc->chip = ioremap(ioc->chip_phys, memap_sz);
> - if (ioc->chip == NULL) {
> - printk(MPT2SAS_ERR_FMT "unable to map "
> - "adapter memory!\n", ioc->name);
> - r = -EINVAL;
> - goto out_fail;
> - }
> }
> }
> }
>
> + if (ioc->chip == NULL) {
> + printk(MPT2SAS_ERR_FMT "unable to map adapter memory! "
> + "or resource not found\n", ioc->name);
> + r = -EINVAL;
> + goto out_fail;
> + }
- Before this patch, the driver probe succeeds even if it can't find an
MMIO resource. That means we would eventually dereference ioc->chip,
which is zero. This patch definitely fixes that bug.
- I raise my eyebrows a little at the "let's use the first MMIO resource
we find" idea. A driver should know exactly which BAR it needs, so it
seems sloppy to search this way. And it's possible that BIOS or the
PCI core set up *one* MMIO BAR, but not the one the driver needs. Then
the search will find the wrong BAR and the driver won't work.
- These drivers both do:
ioc->chip_phys = pci_resource_start(pdev, i);
ioc->chip = ioremap(ioc->chip_phys, memap_sz);
Saving ioc->chip_phys is pointless because it's only used to guard
iounmap(ioc->chip), and the driver probe should fail if it can't find
an MMIO resource, so the places that do the iounmap can assume
ioc->chip is always valid.
- These drivers also search for an I/O resource, but they don't actually
use it, except to print it out. I guess that's harmless, but it seems
sloppy and will print junk on machines where there's no I/O space
available. They do use pci_enable_device_mem(), so at least the device
should work even if no I/O space is available.
- It'd be nice if they used dev_printk() and %pR instead of their ad hoc
formatting.
> _base_mask_interrupts(ioc);
>
> r = _base_get_ioc_facts(ioc, CAN_SLEEP);
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
> index 14a781b..43f87e9 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_base.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
> @@ -1843,7 +1843,8 @@ mpt3sas_base_map_resources(struct MPT3SAS_ADAPTER *ioc)
> goto out_fail;
> }
>
> - for (i = 0, memap_sz = 0, pio_sz = 0 ; i < DEVICE_COUNT_RESOURCE; i++) {
> + for (i = 0, memap_sz = 0, pio_sz = 0; (i < DEVICE_COUNT_RESOURCE) &&
> + (!memap_sz || !pio_sz); i++) {
> if (pci_resource_flags(pdev, i) & IORESOURCE_IO) {
> if (pio_sz)
> continue;
> @@ -1856,15 +1857,16 @@ mpt3sas_base_map_resources(struct MPT3SAS_ADAPTER *ioc)
> chip_phys = (u64)ioc->chip_phys;
> memap_sz = pci_resource_len(pdev, i);
> ioc->chip = ioremap(ioc->chip_phys, memap_sz);
> - if (ioc->chip == NULL) {
> - pr_err(MPT3SAS_FMT "unable to map adapter memory!\n",
> - ioc->name);
> - r = -EINVAL;
> - goto out_fail;
> - }
> }
> }
>
> + if (ioc->chip == NULL) {
> + pr_err(MPT3SAS_FMT "unable to map adapter memory! "
> + " or resource not found\n", ioc->name);
> + r = -EINVAL;
> + goto out_fail;
> + }
> +
> _base_mask_interrupts(ioc);
>
> r = _base_get_ioc_facts(ioc, CAN_SLEEP);
> --
> 2.0.2
>
> --
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