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Message-ID: <7a6df2da-95e8-b2fd-7565-e4b7a51c5b63@gonehiking.org>
Date: Tue, 21 Jun 2022 15:56:58 -0600
From: Khalid Aziz <khalid@...ehiking.org>
To: Arnd Bergmann <arnd@...nel.org>, linux-scsi@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>, Jakub Kicinski <kuba@...nel.org>,
Christoph Hellwig <hch@...radead.org>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>,
iommu@...ts.linux-foundation.org,
"Maciej W . Rozycki" <macro@...am.me.uk>,
Matt Wang <wwentao@...are.com>,
Miquel van Smoorenburg <mikevs@...all.net>,
Mark Salyzyn <salyzyn@...roid.com>,
linuxppc-dev@...ts.ozlabs.org, linux-arch@...r.kernel.org,
linux-alpha@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
linux-parisc@...r.kernel.org, Denis Efremov <efremov@...ux.com>
Subject: Re: [PATCH v2 2/3] scsi: BusLogic remove bus_to_virt
On 6/17/22 06:57, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.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@...am.me.uk>
> Cc: Matt Wang <wwentao@...are.com>
> Cc: Khalid Aziz <khalid@...ehiking.org>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> drivers/scsi/BusLogic.c | 27 ++++++++++++++++-----------
> drivers/scsi/Kconfig | 2 +-
> 2 files changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/scsi/BusLogic.c b/drivers/scsi/BusLogic.c
> index a897c8f914cf..d057abfcdd5c 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)
> {
> /*
> @@ -2540,16 +2554,7 @@ 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);
> + struct blogic_ccb *ccb = blogic_inbox_to_ccb(adapter, adapter->next_inbox);
This change looks good enough as workaround to not use bus_to_virt() for
now. There are two problems I see though. One, I do worry about
blogic_inbox_to_ccb() returning NULL for ccb which should not happen
unless the mailbox pointer was corrupted which would indicate a bigger
problem. Nevertheless a NULL pointer causing kernel panic concerns me.
How about adding a check before we dereference ccb?
Second, with this patch applied, I am seeing errors from the driver:
=====================
[ 1623.902685] sdb: sdb1 sdb2
[ 1623.903245] sd 2:0:0:0: [sdb] Attached SCSI disk
[ 1623.911000] scsi2: Illegal CCB #76 status 2 in Incoming Mailbox
[ 1623.911005] scsi2: Illegal CCB #76 status 2 in Incoming Mailbox
[ 1623.911070] scsi2: Illegal CCB #79 status 2 in Incoming Mailbox
[ 1651.458008] scsi2: Warning: Partition Table appears to have Geometry
256/63 which is
[ 1651.458013] scsi2: not compatible with current BusLogic Host Adapter
Geometry 255/63
[ 1658.797609] scsi2: Resetting BusLogic BT-958D Failed
[ 1659.533208] sd 2:0:0:0: Device offlined - not ready after error recovery
[ 1659.533331] sd 2:0:0:0: Device offlined - not ready after error recovery
[ 1659.533333] sd 2:0:0:0: Device offlined - not ready after error recovery
[ 1659.533342] sd 2:0:0:0: [sdb] tag#101 FAILED Result:
hostbyte=DID_TIME_OUT driverbyte=DRIVER_OK cmd_age=35s
[ 1659.533345] sd 2:0:0:0: [sdb] tag#101 CDB: Read(10) 28 00 00 00 00 28
00 00 10 00
[ 1659.533346] I/O error, dev sdb, sector 40 op 0x0:(READ) flags 0x80700
phys_seg 1 prio class 0
=================
This is on VirtualBox using emulated BusLogic adapter.
This patch needs more refinement.
Thanks,
Khalid
> if (comp_code != BLOGIC_Cn erroneousMD_NOTFOUND) {
> if (ccb->status == BLOGIC_CCB_ACTIVE ||
> ccb->status == BLOGIC_CCB_RESET) {
> diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
> index cf75588a2587..56bdc08d0b77 100644
> --- a/drivers/scsi/Kconfig
> +++ b/drivers/scsi/Kconfig
> @@ -513,7 +513,7 @@ 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
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