On Mon, Jan 13, 2020 at 10:28 AM Prabhakar Kushwaha
<prabhakar.pkin@xxxxxxxxx> wrote:
>
> [Re sending keeping mailing list and others in CC]
>
> On Fri, Jan 10, 2020 at 5:56 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> >
> > [+cc Jens, ahci.c maintainer]
> >
> > On Mon, Jan 06, 2020 at 05:24:44PM +0530, Prabhakar Kushwaha wrote:
> > > Hi All,
> > >
> > > I am trying kexec -e with latest kernel i.e. Linux-5.5.0-rc4. Here
> > > second kernel is not able to detect/mount hard-disk having root file
> > > system (INTEL SSDSC2BB240G7).
> > >
> > > [ 279.690575] ata1: softreset failed (1st FIS failed)
> > > [ 279.695446] ata1: limiting SATA link speed to 3.0 Gbps
> > > [ 280.910020] ata1: SATA link down (SStatus 0 SControl 320)
> > > [ 282.626018] ata1: SATA link down (SStatus 0 SControl 300)
> > > [ 282.631409] ata1: link online but 1 devices misclassified, retrying
> > > [ 282.637665] ata1: reset failed (errno=-11), retrying in 9 secs
> > > [ 298.294546] ata1: failed to reset engine (errno=-5)
> > > [ 302.042967] ata1: softreset failed (1st FIS failed)
> > > [ 308.798609] ata1: failed to reset engine (errno=-5)
> > > [ 337.546605] ata1: softreset failed (1st FIS failed)
> > > [ 337.551475] ata1: limiting SATA link speed to 3.0 Gbps
> > > [ 338.766022] ata1: SATA link down (SStatus 0 SControl 320)
> > > [ 339.270943] ata1: EH pending after 5 tries, giving up
> > >
> > > I found following two workaround for this issue.
> > > A) Define ".shutdown" in driver/ata/ahci.c.
> > >
> > > reboot --> kernel_kexec() --> kernel_restart_prepare() -->
> > > device_shutdown() --> pci_device_shutdown() --> ahci_shutdown_one()
> > > --> new function
> > >
> > > diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> > > index 4bfd1b14b390..50a101002885 100644
> > > --- a/drivers/ata/ahci.c
> > > +++ b/drivers/ata/ahci.c
> > > @@ -81,6 +81,7 @@ enum board_ids {
> > >
> > > static int ahci_init_one(struct pci_dev *pdev, const struct
> > > pci_device_id *ent);
> > > static void ahci_remove_one(struct pci_dev *dev);
> > > +static void ahci_shutdown_one(struct pci_dev *dev);
> > > static int ahci_vt8251_hardreset(struct ata_link *link, unsigned int *class,
> > > unsigned long deadline);
> > > static int ahci_avn_hardreset(struct ata_link *link, unsigned int *class,
> > > @@ -606,6 +607,7 @@ static struct pci_driver ahci_pci_driver = {
> > > .id_table = ahci_pci_tbl,
> > > .probe = ahci_init_one,
> > > .remove = ahci_remove_one,
> > > + .shutdown = ahci_shutdown_one,
> > > .driver = {
> > > .pm = &ahci_pci_pm_ops,
> > > },
> > >
> > > +static void ahci_shutdown_one(struct pci_dev *pdev)
> > > +{
> > > + pm_runtime_get_noresume(&pdev->dev);
> > > + ata_pci_remove_one(pdev);
> > > +}
> > > +
> > > Note: After defining shutdown, error related to file-system write
> > > seen. Looks like even after device_shutdown, file system related
> > > transaction goes to disk.
> > >
> > > B)) Commenting of pci_clear_master() from pci_device_shutdown()
> > > reboot --> kernel_kexec() --> kernel_restart_prepare() -->
> > > device_shutdown() --> pci_device_shutdown()
> > >
> > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > > index 0454ca0e4e3f..ddffaa9321bb 100644
> > > --- a/drivers/pci/pci-driver.c
> > > +++ b/drivers/pci/pci-driver.c
> > > @@ -481,8 +481,10 @@ static void pci_device_shutdown(struct device *dev)
> > > /*
> > > * If this is a kexec reboot, turn off Bus Master bit on the
> > > @@ -491,8 +493,16 @@ static void pci_device_shutdown(struct device *dev)
> > > * If it is not a kexec reboot, firmware will hit the PCI
> > > * devices with big hammer and stop their DMA any way.
> > > */
> > >
> > > - if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot))
> > > - pci_clear_master(pci_dev);
> >
> > I doubt we would remove this without a much clearer justification.
> >
> > > Here pci_dev current_state. It is "0" i.e. D0.
> > >
> > > From A and B. Looks like even after pci_clear_master(), Some DMA
> > > transactions going on PCIe device causing device in unstable.
> > > Not sure if this is the reason and how to solve this problem.
> >
> > Is it possible the ahci driver depends on receiving the device with
> > bus mastering already enabled? I would guess that would be the common
> > case in a non-kexec boot -- the BIOS probably hands off the device
> > with bus mastering enabled.
> >
>
> Above code clearing Bus Master. May be it try to make sure that next
> kernel get PCIe in same state in which BIOS could have provided.
> Not sure why this is causing issue in our case. Need to debug more.
>
I added more prints and added stack dump in ata_scsi_queuecmd().
I found that lots of syscall __arm64_sys_fsync() happens for file
system sync during kexec -e. These calls happens even after clearing
PCIe Bus Master i.e. "M" bit.
This should not happen as it may unstable SATA. I believe this is the
reason second kernel is not able to detect SATA hard-disk.
Note: This behavior is random, sometime working code start showing
this error. Also different Linux tags(5.5-RC4, 5.5-RC6, 5.5-RC7) have
different behavior on our platform (ARM64 Thunder X2).
Once PCIe Bust Master i.e. "M" bit is cleared,
a) either file system sysnc should not happen
b) or no transaction should go on SATA.
Please suggest how to avoid "a". once "M" bit cleared.
for "b", should setting port flag as ATA_PFLAG_FROZEN be enough in
driver/ata/ahci.c?
ap->pflags |= ATA_PFLAG_FROZEN;
Please suggest..
--pk
[ 126.025134] ata_scsi_queuecmd 4393: dump
[ 126.029052] CPU: 42 PID: 3144 Comm: journal-offline Not tainted
5.5.0-rc6+ #110
[ 126.036346] Hardware name: Cavium Inc. Saber/Saber, BIOS
TX2-FW-Release-7.4-build_05 08/24/2019
[ 126.045029] Call trace:
[ 126.047463] dump_backtrace+0x0/0x1f8
[ 126.051112] show_stack+0x24/0x30
[ 126.054414] dump_stack+0xbc/0x104
[ 126.057802] ata_scsi_queuecmd+0x30c/0x338
[ 126.061886] scsi_queue_rq+0x80c/0xb70
[ 126.065623] blk_mq_dispatch_rq_list+0xac/0x688
[ 126.070140] blk_mq_do_dispatch_sched+0x6c/0x110
[ 126.074744] blk_mq_sched_dispatch_requests+0x130/0x220
[ 126.079956] __blk_mq_run_hw_queue+0x98/0x160
[ 126.084300] __blk_mq_delay_run_hw_queue+0x188/0x1c8
[ 126.089250] blk_mq_run_hw_queue+0x5c/0x110
[ 126.093421] blk_mq_sched_insert_requests+0x90/0x168
[ 126.098372] blk_mq_flush_plug_list+0x1ac/0x308
[ 126.102889] blk_flush_plug_list+0xdc/0x110
[ 126.107059] blk_finish_plug+0x3c/0x228
[ 126.110883] ext4_writepages+0x460/0xbd8
[ 126.114793] do_writepages+0x5c/0x108
[ 126.118442] __filemap_fdatawrite_range+0x128/0x180
[ 126.123306] file_write_and_wait_range+0x94/0xf8
[ 126.127910] ext4_sync_file+0x11c/0x460
[ 126.131732] vfs_fsync_range+0x4c/0x88
[ 126.135468] do_fsync+0x48/0x78
[ 126.138596] __arm64_sys_fsync+0x24/0x38
[ 126.142506] el0_svc_common.constprop.2+0x78/0x168
[ 126.147283] el0_svc_handler+0x34/0xa0
[ 126.151019] el0_sync_handler+0xe4/0x188
[ 126.154928] el0_sync+0x164/0x180
[ 126.158241] :__ata_scsi_queuecmd 4321
[ 126.161893] ata_scsi_translate 1999
[ 126.165368] ten-byte command
[ 126.168236] ahci_pmp_qc_defer 1678
[ 126.171624] ahci_qc_prep 1696
[ 126.174577] ahci_fill_sg 1655
[ 126.177532] ahci_qc_issue 2058
[ 126.180572] EXIT
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