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Date: Thu, 5 Aug 2021 16:49:03 +0800 From: Dongdong Liu <liudongdong3@...wei.com> To: Logan Gunthorpe <logang@...tatee.com>, <helgaas@...nel.org>, <hch@...radead.org>, <kw@...ux.com>, <leon@...nel.org>, <linux-pci@...r.kernel.org>, <rajur@...lsio.com>, <hverkuil-cisco@...all.nl> CC: <linux-media@...r.kernel.org>, <netdev@...r.kernel.org> Subject: Re: [PATCH V7 9/9] PCI/P2PDMA: Add a 10-Bit Tag check in P2PDMA Hi Logan Many thanks for your review. On 2021/8/4 23:56, Logan Gunthorpe wrote: > > > On 2021-08-04 7:47 a.m., Dongdong Liu wrote: >> Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with >> 10-Bit Tag Requester doesn't interact with a device that does not >> support 10-BIT Tag Completer. Before that happens, the kernel should >> emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to >> disable 10-BIT Tag Requester for PF device. >> "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable >> 10-BIT Tag Requester for VF device. >> >> Signed-off-by: Dongdong Liu <liudongdong3@...wei.com> >> --- >> drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 40 insertions(+) >> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c >> index 50cdde3..948f2be 100644 >> --- a/drivers/pci/p2pdma.c >> +++ b/drivers/pci/p2pdma.c >> @@ -19,6 +19,7 @@ >> #include <linux/random.h> >> #include <linux/seq_buf.h> >> #include <linux/xarray.h> >> +#include "pci.h" >> >> enum pci_p2pdma_map_type { >> PCI_P2PDMA_MAP_UNKNOWN = 0, >> @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) >> (client->bus->number << 8) | client->devfn; >> } >> >> +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, >> + bool verbose) >> +{ >> + bool req; >> + bool comp; >> + u16 ctl2; >> + >> + if (a->is_virtfn) { >> +#ifdef CONFIG_PCI_IOV >> + req = !!(a->physfn->sriov->ctrl & >> + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); >> +#endif >> + } else { >> + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2); >> + req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); >> + } >> + >> + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); >> + if (req && (!comp)) { > > I think the brackets around !comp are unnecessary. Yes, will fix. > >> + if (verbose) { >> + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n", >> + pci_name(a), pci_name(b)); >> + if (a->is_virtfn) >> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/sriov_vf_10bit_tag_ctl\n", >> + pci_name(a)); >> + else >> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/10bit_tag\n", >> + pci_name(a)); > > Can we not simplify this slightly by having a const char * set to the > tag in the above if (a->is_virtfn)? > > pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > > /sys/bus/pci/devices/%s/%s\n", pci_name(a), tag); Good point, will fix. Thanks, Dongdong > >> + } >> + return false; >> + } >> + >> + return true; >> +} >> + >> /* >> * Calculate the P2PDMA mapping type and distance between two PCI devices. >> * >> @@ -532,6 +568,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, >> map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> } >> done: >> + if (!check_10bit_tags_vaild(client, provider, verbose) || >> + !check_10bit_tags_vaild(provider, client, verbose)) >> + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> + >> rcu_read_lock(); >> p2pdma = rcu_dereference(provider->p2pdma); >> if (p2pdma) >> > . >
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