Messages in this thread | | | Subject | Re: [PATCH] vfio/pci: Support error recovery | From | Cao jin <> | Date | Mon, 28 Nov 2016 17:32:15 +0800 |
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On 11/28/2016 11:00 AM, Michael S. Tsirkin wrote: > On Sun, Nov 27, 2016 at 07:34:17PM +0800, Cao jin wrote: >> It is user space driver's or device-specific driver's(in guest) responsbility >> to do a serious recovery when error happened. Link-reset is one part of >> recovery, when pci device is assigned to VM via vfio, link-reset will do >> twice in host & guest separately, which will cause many trouble for a >> successful recovery, so, disable the vfio-pci's link-reset in aer driver >> in host, this is a keypoint for guest to do error recovery successfully. >> >> CC: alex.williamson@redhat.com >> CC: mst@redhat.com >> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com> >> --- >> This is actually a RFC version(has debug lines left), and has minor changes in >> aer driver, so I think maybe it is better not to CC pci guys in this round. >> Later will do. >> >> drivers/pci/pcie/aer/aerdrv_core.c | 12 ++++++- >> drivers/vfio/pci/vfio_pci.c | 63 +++++++++++++++++++++++++++++++++++-- >> drivers/vfio/pci/vfio_pci_private.h | 2 ++ >> 3 files changed, 74 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c >> index 521e39c..289fb8e 100644 >> --- a/drivers/pci/pcie/aer/aerdrv_core.c >> +++ b/drivers/pci/pcie/aer/aerdrv_core.c >> @@ -496,7 +496,17 @@ static void do_recovery(struct pci_dev *dev, int severity) >> "error_detected", >> report_error_detected); >> >> - if (severity == AER_FATAL) { >> + /* vfio-pci as a general meta driver, it actually couldn't do any real >> + * recovery for device. It is user space driver, or device-specific >> + * driver in guest who should take care of the serious error recovery, >> + * link reset actually is one part of whole recovery. Doing reset_link >> + * in aer driver of host kernel for vfio-pci devices will cause many >> + * trouble for user space driver or guest's device-specific driver, >> + * for example: the serious recovery often need to read register in >> + * config space, but if register reading happens during link-resetting, >> + * it is quite possible to return invalid value like all F's, which >> + * will result in unpredictable error. */ > > Fix multi-comment style please. > >> + if (severity == AER_FATAL && strcmp(dev->driver->name, "vfio-pci")) { > > You really want some flag in the device, or something similar. > Also, how do we know driver is not going away at this point? >
I didn't think of this condition, and I don't quite follow how would driver go away?(device has error happened, then is removed?)
>> result = reset_link(dev); >> if (result != PCI_ERS_RESULT_RECOVERED) >> goto failed;
>> @@ -1187,10 +1200,30 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev, >> return PCI_ERS_RESULT_DISCONNECT; >> } >> >> + /* get device's uncorrectable error status as soon as possible, >> + * and signal it to user space. The later we read it, the possibility >> + * the register value is mangled grows. */ >> + aer_cap_offset = pci_find_ext_capability(vdev->pdev, PCI_EXT_CAP_ID_ERR); >> + ret = pci_read_config_dword(vdev->pdev, aer_cap_offset + >> + PCI_ERR_UNCOR_STATUS, &uncor_status); >> + if (ret) >> + return PCI_ERS_RESULT_DISCONNECT; >> + >> + pr_err("device %d got AER detect notification. uncorrectable error status = 0x%x\n", pdev->devfn, uncor_status);//to be removed >> mutex_lock(&vdev->igate); >> + >> + vdev->aer_recovering = true; >> + reinit_completion(&vdev->aer_error_completion); >> + >> + /* suspend config space access from user space, >> + * when vfio-pci's error recovery process is on */ > > what about access to memory etc? Do you need to suspend this as well? >
Yes, this question came into my mind a little bit, but I didn't see some existing APIs like pci_cfg_access_xxx which can help to do this.(I am still not familiar with kernel)
>> + pci_cfg_access_trylock(vdev->pdev); > > If you trylock, you need to handle failure.
try lock returns 0 if access is already locked, 1 otherwise. Is it necessary to check its return value?
-- Sincerely, Cao jin
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