Re: [PATCH v3 1/3] scsi: BusLogic remove bus_to_virt

Khalid Aziz
2022-06-24T16:38:35Z

On 6/24/22 09:52, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> The BusLogic driver is the last remaining driver that relies on the
> deprecated bus_to_virt() function, which in turn only works on a few
> architectures, and is incompatible with both swiotlb and iommu support.
>
> Before commit 391e2f25601e ("[SCSI] BusLogic: Port driver to 64-bit."),
> the driver had a dependency on x86-32, presumably because of this
> problem. However, the change introduced another bug that made it still
> impossible to use the driver on any 64-bit machine.
>
> This was in turn fixed in commit 56f396146af2 ("scsi: BusLogic: Fix
> 64-bit system enumeration error for Buslogic"), 8 years later, which
> shows that there are not a lot of users.
>
> Maciej is still using the driver on 32-bit hardware, and Khalid mentioned
> that the driver works with the device emulation used in VirtualBox
> and VMware. Both of those only emulate it for Windows 2000 and older
> operating systems that did not ship with the better LSI logic driver.
>
> Do a minimum fix that searches through the list of descriptors to find
> one that matches the bus address. This is clearly as inefficient as
> was indicated in the code comment about the lack of a bus_to_virt()
> replacement. A better fix would likely involve changing out the entire
> descriptor allocation for a simpler one, but that would be much
> more invasive.
>
> Cc: Maciej W. Rozycki <macro@orcam.me.uk>
> Cc: Matt Wang <wwentao@vmware.com>
> Tested-by: Khalid Aziz <khalid@gonehiking.org>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> v3: Address issues pointed out by Khalid Aziz
> v2: Attempt to fix the driver instead of removing it
> ---
> drivers/scsi/BusLogic.c | 35 +++++++++++++++++++++++------------
> drivers/scsi/Kconfig | 2 +-
> 2 files changed, 24 insertions(+), 13 deletions(-)
>

This looks good.

Acked-by: Khalid Aziz <khalid@gonehiking.org>

> diff --git a/drivers/scsi/BusLogic.c b/drivers/scsi/BusLogic.c
> index a897c8f914cf..f2abffce2659 100644
> --- a/drivers/scsi/BusLogic.c
> +++ b/drivers/scsi/BusLogic.c
> @@ -2515,12 +2515,26 @@ static int blogic_resultcode(struct blogic_adapter *adapter,
> return (hoststatus << 16) | tgt_status;
> }
>
> +/*
> + * turn the dma address from an inbox into a ccb pointer
> + * This is rather inefficient.
> + */
> +static struct blogic_ccb *
> +blogic_inbox_to_ccb(struct blogic_adapter *adapter, struct blogic_inbox *inbox)
> +{
> + struct blogic_ccb *ccb;
> +
> + for (ccb = adapter->all_ccbs; ccb; ccb = ccb->next_all)
> + if (inbox->ccb == ccb->dma_handle)
> + break;
> +
> + return ccb;
> +}
>
> /*
> blogic_scan_inbox scans the Incoming Mailboxes saving any
> Incoming Mailbox entries for completion processing.
> */
> -
> static void blogic_scan_inbox(struct blogic_adapter *adapter)
> {
> /*
> @@ -2540,17 +2554,14 @@ static void blogic_scan_inbox(struct blogic_adapter *adapter)
> enum blogic_cmplt_code comp_code;
>
> while ((comp_code = next_inbox->comp_code) != BLOGIC_INBOX_FREE) {
> - /*
> - We are only allowed to do this because we limit our
> - architectures we run on to machines where bus_to_virt(
> - actually works. There *needs* to be a dma_addr_to_virt()
> - in the new PCI DMA mapping interface to replace
> - bus_to_virt() or else this code is going to become very
> - innefficient.
> - */
> - struct blogic_ccb *ccb =
> - (struct blogic_ccb *) bus_to_virt(next_inbox->ccb);
> - if (comp_code != BLOGIC_CMD_NOTFOUND) {
> + struct blogic_ccb *ccb = blogic_inbox_to_ccb(adapter, next_inbox);
> + if (!ccb) {
> + /*
> + * This should never happen, unless the CCB list is
> + * corrupted in memory.
> + */
> + blogic_warn("Could not find CCB for dma address %x\n", adapter, next_inbox->ccb);
> + } else if (comp_code != BLOGIC_CMD_NOTFOUND) {
> if (ccb->status == BLOGIC_CCB_ACTIVE ||
> ccb->status == BLOGIC_CCB_RESET) {
> /*
> diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
> index 6e3a04107bb6..689186f3a908 100644
> --- a/drivers/scsi/Kconfig
> +++ b/drivers/scsi/Kconfig
> @@ -514,7 +514,7 @@ config SCSI_HPTIOP
>
> config SCSI_BUSLOGIC
> tristate "BusLogic SCSI support"
> - depends on PCI && SCSI && VIRT_TO_BUS
> + depends on PCI && SCSI
> help
> This is support for BusLogic MultiMaster and FlashPoint SCSI Host
> Adapters. Consult the SCSI-HOWTO, available from