Sorry for a delayed response. > -----Original Message----- > From: Bjorn Helgaas [mailto:bhelgaas@xxxxxxxxxx] > Sent: Tuesday, November 04, 2014 11:05 PM > To: Venkat Duvvuru > Cc: linux-pci@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v1] pci: Limit VPD length of Emulex adapters to the > actual length supported. > > > In this case when the host reads 32k space, the adapter gets around 8K > interrupts and sometimes gets overwhelmed with the interrupt storm. This > could cause the adapter to stop functioning properly. > > Limiting the VPD read to 1K causes only 256 interrupts (on the adapter) and > the problem never seems to occur. > > This has been the main motivation behind my patch. > > I do agree that the timeout could still occur even when reading the 1K > implemented space, but I feel it's highly improbable. > > OK. I would guess that something like > > while /bin/true; do > cat /sys/devices/pci0000:00/0000:00:00.0/vpd > done > > could still overwhelm the adapter, even with the 1K limit in place. Correct. > > > As an alternative solution, would you be open to a fix in PCI -core to stop > reading after the End-tag is detected? (This logic is used by pci-utility (ls- > vpd.c) while reading VPD data.) > > I now feel that this is the *right* solution than my pci-quirks patch. > > That's a possibility, and if we were implementing VPD support from > scratch, I'd probably do it that way. > > My only concern with changing now is that it could break existing > users for devices where the VPD content doesn't have the structure > specified by the spec. There aren't *too* many users of > pci_read_vpd() in the tree, so it might be feasible to just ask the > bnx2x, tg3, cxgb4, sky2, and efx folks whether they think it's safe. > > I took a quick look at those drivers, and it actually looks like most > of them look for the tag structure, e.g., by using pci_vpd_find_tag() > or doing something similar. So maybe it actually would be safe to do > this. Maybe you could have a more thorough look at them and see if > you agree? If the devices doesn't follow the spec for the VPD contents, pci-core may endup requesting 32k data which probably will not break existing users. I looked into all the pci_read_vpd users (drivers) and they seem to be doing pci_find_vpd_tag or pci_vpd_find_info_keyword to find a specific tag/keyword and not all the tags/keywords. A safer approach probably is to look for the end tag in pci_read_vpd, if offset is "zero" because some drivers are doing "pci_read_vpd" with a non-zero offset. /Venkat. ��.n��������+%������w��{.n�����{���"�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
