RE: [EXT] Re: [PATCH v12 6/6] PCI: endpoint: Add vNTB MSI support

From: Frank Li
Date: Fri Oct 07 2022 - 10:55:10 EST

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In reply to: Lorenzo Pieralisi: "Re: [PATCH v12 6/6] PCI: endpoint: Add vNTB MSI support"
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> -----Original Message-----
> From: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
> Sent: Friday, October 7, 2022 4:16 AM
> To: Frank Li <frank.li@xxxxxxx>
> Cc: maz@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; robh+dt@xxxxxxxxxx;
> krzysztof.kozlowski+dt@xxxxxxxxxx; shawnguo@xxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; kw@xxxxxxxxx; bhelgaas@xxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; Peng Fan
> <peng.fan@xxxxxxx>; Aisheng Dong <aisheng.dong@xxxxxxx>;
> jdmason@xxxxxxxx; kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; dl-linux-
> imx <linux-imx@xxxxxxx>; kishon@xxxxxx; lorenzo.pieralisi@xxxxxxx;
> ntb@xxxxxxxxxxxxxxx; lznuaa@xxxxxxxxx; imx@xxxxxxxxxxxxxxx;
> manivannan.sadhasivam@xxxxxxxxxx
> Subject: [EXT] Re: [PATCH v12 6/6] PCI: endpoint: Add vNTB MSI support
>
> Caution: EXT Email
>
> On Thu, Sep 22, 2022 at 11:12:46AM -0500, Frank Li wrote:
> > ┌───────┐ ┌──────────┐
> > │ │ │ │
> > ┌─────────────┐ │ PCI │ │ PCI Host │
> > │ MSI │◄┐ │ EP │ │ │
> > │ Controller │ │ │ │ 3.MSI Write │ │
> > └────────┬────┘ └─┼───────┼────
> ───────────────┤ │
> > ▲ │ │ │ ├─BAR_n │
> > │ └────────┼───────┼─────────
> ─────────►│ │
> > │ │ │ 2.Call Back │ │
> > │ │ │ write_msi_msg() │ │
> > │ │ │ │ │
> > │ └───┬───┘ └──────────┘
> > │ │
> > └───────────────────┘
> > 1.platform_msi_domain_alloc_irqs()
> >
> > There is no defined way of raising IRQs by PCI host to the PCI endpoint.
> > Only define MSI/MSI-X to let EP notified RC status change.
>
> This picture is misleading, especially (2).
[Frank Li] what's your suggestion? (2) Move into PCI-EP block
Or totally remove picture?

> IIUC all this patch is
> doing is implementing an NTB DB in the EP, that's it, we should
> reword the commit log as such.

[Frank Li] Previously use poll method as NTB DB.
Now add use Platform MSI as DB.
what you specific suggestion?

>
> We are in the merge window - it is very likely this patch should
> be postponed to v6.2, I didn't notice that the IRQchip changes
> went in - apologies.
>
> > The memory assigned for BAR region by the PCI host is mapped to the
> > message address of platform msi interrupt controller in PCI Endpoint.
> > Such that, whenever the PCI host writes to the BAR region, it will
> > trigger an IRQ in the Endpoint.
> >
> > Basic working follow as
> > 1. EP function driver call platform_msi_domain_alloc_irqs() alloc a
> > MSI irq from MSI controller with call back function write_msi_msg();
> > 2. write_msg_msg will config BAR and map to address defined in msi_msg;
> > 3. Host side trigger an IRQ in Endpoint by write to BAR region.
> >
> > Add MSI support for pci-epf-vntb. Query if system has an MSI controller.
> > Set up doorbell address according to struct msi_msg.
> >
> > So PCI RC can write this doorbell address to trigger EP side's IRQ.
> >
> > If no MSI controller exists, fall back to software polling.
> >
> > Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> > ---
> > drivers/pci/endpoint/functions/pci-epf-vntb.c | 148 +++++++++++++++---
> > 1 file changed, 127 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > index acea753af29ed..8fdeac2201e29 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > @@ -44,6 +44,7 @@
> > #include <linux/pci-epc.h>
> > #include <linux/pci-epf.h>
> > #include <linux/ntb.h>
> > +#include <linux/msi.h>
> >
> > static struct workqueue_struct *kpcintb_workqueue;
> >
> > @@ -137,11 +138,14 @@ struct epf_ntb {
> > struct epf_ntb_ctrl *reg;
> >
> > u32 *epf_db;
> > + phys_addr_t epf_db_phys;
> >
> > phys_addr_t vpci_mw_phy[MAX_MW];
> > void __iomem *vpci_mw_addr[MAX_MW];
> >
> > struct delayed_work cmd_handler;
> > +
> > + int msi_virqbase;
> > };
> >
> > #define to_epf_ntb(epf_group) container_of((epf_group), struct epf_ntb,
> group)
> > @@ -256,10 +260,13 @@ static void epf_ntb_cmd_handler(struct
> work_struct *work)
> >
> > ntb = container_of(work, struct epf_ntb, cmd_handler.work);
> >
> > - for (i = 1; i < ntb->db_count; i++) {
> > - if (ntb->epf_db[i]) {
> > - ntb_db_event(&ntb->ntb, i);
> > - ntb->epf_db[i] = 0;
> > + if (!ntb->epf_db_phys) {
> > + for (i = 1; i < ntb->db_count; i++) {
> > + if (ntb->epf_db[i]) {
> > + ntb->db |= 1 << (i - 1);
> > + ntb_db_event(&ntb->ntb, i);
> > + ntb->epf_db[i] = 0;
> > + }
> > }
> > }
> >
> > @@ -464,7 +471,7 @@ static int epf_ntb_config_spad_bar_alloc(struct
> epf_ntb *ntb)
> >
> > for (i = 0; i < ntb->db_count; i++) {
> > ntb->reg->db_data[i] = 1 + i;
> > - ntb->reg->db_offset[i] = 0;
> > + ntb->reg->db_offset[i] = sizeof(u32) * i;
>
> Why sizeof(u32) ?

[Frank Li] In https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/ntb/hw/epf/ntb_hw_epf.c
Line 488:
writel(db_data, ndev->db_reg + (db_entry_size * interrupt_num) +
db_offset);

We now set db_entry_size is 0.
Directly use db_offset as DB register offset.
Each DB register is u32.

>
> > }
> >
> > return 0;
> > @@ -517,6 +524,28 @@ static int epf_ntb_configure_interrupt(struct
> epf_ntb *ntb)
> > return 0;
> > }
> >
> > +static int epf_ntb_db_size(struct epf_ntb *ntb)
> > +{
> > + const struct pci_epc_features *epc_features;
> > + size_t size = sizeof(u32) * ntb->db_count;
>

[Frank Li] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/ntb/hw/epf/ntb_hw_epf.c
Use u32 as DB register size.

> Same question.
>
> > + u32 align;
> > +
> > + epc_features = pci_epc_get_features(ntb->epf->epc,
> > + ntb->epf->func_no,
> > + ntb->epf->vfunc_no);
> > + align = epc_features->align;
> > +
> > + if (size < 128)
> > + size = 128;
> > +
> > + if (align)
> > + size = ALIGN(size, align);
> > + else
> > + size = roundup_pow_of_two(size);
> > +
> > + return size;
> > +}
> > +
> > /**
> > * epf_ntb_db_bar_init() - Configure Doorbell window BARs
> > * @ntb: NTB device that facilitates communication between HOST and
> VHOST
> > @@ -540,27 +569,26 @@ static int epf_ntb_db_bar_init(struct epf_ntb
> *ntb)
> > ntb->epf->func_no,
> > ntb->epf->vfunc_no);
> > align = epc_features->align;
> > -
> > - if (size < 128)
> > - size = 128;
> > -
> > - if (align)
> > - size = ALIGN(size, align);
> > - else
> > - size = roundup_pow_of_two(size);
> > + size = epf_ntb_db_size(ntb);
> >
> > barno = ntb->epf_ntb_bar[BAR_DB];
> > + epf_bar = &ntb->epf->bar[barno];
> >
> > - mw_addr = pci_epf_alloc_space(ntb->epf, size, barno, align, 0);
> > - if (!mw_addr) {
> > - dev_err(dev, "Failed to allocate OB address\n");
> > - return -ENOMEM;
> > + if (ntb->epf_db_phys) {
> > + mw_addr = NULL;
> > + epf_bar->phys_addr = ntb->epf_db_phys;
> > + epf_bar->barno = barno;
> > + epf_bar->size = size;
> > + } else {
> > + mw_addr = pci_epf_alloc_space(ntb->epf, size, barno, align, 0);
> > + if (!mw_addr) {
> > + dev_err(dev, "Failed to allocate doorbell address\n");
> > + return -ENOMEM;
> > + }
> > }
> >
> > ntb->epf_db = mw_addr;
> >
> > - epf_bar = &ntb->epf->bar[barno];
> > -
> > ret = pci_epc_set_bar(ntb->epf->epc, ntb->epf->func_no, ntb->epf-
> >vfunc_no, epf_bar);
> > if (ret) {
> > dev_err(dev, "Doorbell BAR set failed\n");
> > @@ -719,6 +747,83 @@ static int epf_ntb_init_epc_bar(struct epf_ntb
> *ntb)
> > return 0;
> > }
> >
> > +#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
> > +static void epf_ntb_write_msi_msg(struct msi_desc *desc, struct msi_msg
> *msg)
> > +{
> > + struct epf_ntb *ntb = dev_get_drvdata(desc->dev);
> > + struct epf_ntb_ctrl *reg = ntb->reg;
> > + int size = epf_ntb_db_size(ntb);
> > + u64 addr;
> > +
> > + addr = msg->address_hi;
> > + addr <<= 32;
> > + addr |= msg->address_lo;
> > +
> > + reg->db_data[desc->msi_index] = msg->data;
> > +
> > + if (!desc->msi_index)
> > + ntb->epf_db_phys = round_down(addr, size);
> > +
> > + reg->db_offset[desc->msi_index] = addr - ntb->epf_db_phys;
> > +}
> > +#endif
>
> Can we move this hunk down into the same #ifdef guard please ?
>
> > +static irqreturn_t epf_ntb_interrupt_handler(int irq, void *data)
> > +{
> > + struct epf_ntb *ntb = data;
> > + int index;
> > +
> > + index = irq - ntb->msi_virqbase;
> > + ntb->db |= 1 << (index - 1);
> > + ntb_db_event(&ntb->ntb, index);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
> > +static void epf_ntb_epc_msi_init(struct epf_ntb *ntb)
> > +{
> > + struct device *dev = &ntb->epf->dev;
> > + struct irq_domain *domain;
> > + int virq;
> > + int ret;
> > + int i;
> > +
> > + domain = dev_get_msi_domain(ntb->epf->epc->dev.parent);
> > + if (!domain)
> > + return;
> > +
> > + dev_set_msi_domain(dev, domain);
> > +
> > + if (platform_msi_domain_alloc_irqs(&ntb->epf->dev,
> > + ntb->db_count,
> > + epf_ntb_write_msi_msg)) {
> > + dev_err(dev, "Can't allocate MSI, falling back to polling mode\n");
> > + return;
> > + }
> > + dev_info(dev, "Using MSI as doorbell\n");
>
> Is it really useful to print this in the kernel log ? dev_dbg seems more
> suitable to me.
>
> > +
> > + for (i = 0; i < ntb->db_count; i++) {
> > + virq = msi_get_virq(dev, i);
> > + ret = devm_request_irq(dev, virq,
> > + epf_ntb_interrupt_handler, 0,
> > + "pci_epf_vntb", ntb);
> > +
> > + if (ret) {
> > + dev_err(dev, "Failed to request doorbell IRQ! Falling back to
> polling mode");
> > + ntb->epf_db_phys = 0;
> > + break;
>
> Doesn't this require a platform_msi_domain_free_irqs() ?
[Frank Li] you are right.

>
> Thanks,
> Lorenzo
>
> > + }
> > +
> > + if (!i)
> > + ntb->msi_virqbase = virq; /* msi start virq number */
> > + }
> > +}
> > +#else
> > +static void epf_ntb_epc_msi_init(struct epf_ntb *ntb)
> > +{
> > +}
> > +#endif /* CONFIG_GENERIC_MSI_IRQ_DOMAIN */
> > /**
> > * epf_ntb_epc_init() - Initialize NTB interface
> > * @ntb: NTB device that facilitates communication between HOST and
> VHOST
> > @@ -1320,14 +1425,15 @@ static int epf_ntb_bind(struct pci_epf *epf)
> > goto err_bar_alloc;
> > }
> >
> > + epf_set_drvdata(epf, ntb);
> > + epf_ntb_epc_msi_init(ntb);
> > +
> > ret = epf_ntb_epc_init(ntb);
> > if (ret) {
> > dev_err(dev, "Failed to initialize EPC\n");
> > goto err_bar_alloc;
> > }
> >
> > - epf_set_drvdata(epf, ntb);
> > -
> > pci_space[0] = (ntb->vntb_pid << 16) | ntb->vntb_vid;
> > pci_vntb_table[0].vendor = ntb->vntb_vid;
> > pci_vntb_table[0].device = ntb->vntb_pid;
> > --
> > 2.35.1
> >

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