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[v9,4/4] PCI: endpoint: Add vNTB MSI support

Message ID 20220907034856.3101570-5-Frank.Li@nxp.com (mailing list archive)
State New, archived
Headers show
Series [v9,1/4] irqchip: allow pass down .pm field at IRQCHIP_PLATFORM_DRIVER_END | expand

Commit Message

Frank Li Sept. 7, 2022, 3:48 a.m. UTC
┌───────┐                   ┌──────────┐
                      │       │                   │          │
    ┌─────────────┐   │ 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.

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@nxp.com>
---
 drivers/pci/endpoint/functions/pci-epf-vntb.c | 155 +++++++++++++++---
 1 file changed, 128 insertions(+), 27 deletions(-)

Comments

kernel test robot Sept. 7, 2022, 8:43 p.m. UTC | #1
Hi Frank,

I love your patch! Perhaps something to improve:

[auto build test WARNING on jonmason-ntb/ntb-next]
[also build test WARNING on robh/for-next linus/master v6.0-rc4 next-20220907]
[cannot apply to tip/irq/core]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Frank-Li/PCI-EP-driver-support-MSI-doorbell-from-host/20220907-115114
base:   https://github.com/jonmason/ntb ntb-next
config: loongarch-randconfig-s052-20220906 (https://download.01.org/0day-ci/archive/20220908/202209080437.cNpaoZXx-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 12.1.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://github.com/intel-lab-lkp/linux/commit/0fe017b7ce1e4748acce80d9ddb81b3cd456adbb
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Frank-Li/PCI-EP-driver-support-MSI-doorbell-from-host/20220907-115114
        git checkout 0fe017b7ce1e4748acce80d9ddb81b3cd456adbb
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=loongarch SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

sparse warnings: (new ones prefixed by >>)
>> drivers/pci/endpoint/functions/pci-epf-vntb.c:567:25: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void [noderef] __iomem *[assigned] mw_addr @@     got void * @@
   drivers/pci/endpoint/functions/pci-epf-vntb.c:567:25: sparse:     expected void [noderef] __iomem *[assigned] mw_addr
   drivers/pci/endpoint/functions/pci-epf-vntb.c:567:25: sparse:     got void *
   drivers/pci/endpoint/functions/pci-epf-vntb.c:600:41: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void *addr @@     got void [noderef] __iomem *epf_db @@
   drivers/pci/endpoint/functions/pci-epf-vntb.c:600:41: sparse:     expected void *addr
   drivers/pci/endpoint/functions/pci-epf-vntb.c:600:41: sparse:     got void [noderef] __iomem *epf_db
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1206:33: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected void [noderef] __iomem *base @@     got struct epf_ntb_ctrl *reg @@
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1206:33: sparse:     expected void [noderef] __iomem *base
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1206:33: sparse:     got struct epf_ntb_ctrl *reg
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1217:33: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected void [noderef] __iomem *base @@     got struct epf_ntb_ctrl *reg @@
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1217:33: sparse:     expected void [noderef] __iomem *base
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1217:33: sparse:     got struct epf_ntb_ctrl *reg
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1228:33: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected void [noderef] __iomem *base @@     got struct epf_ntb_ctrl *reg @@
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1228:33: sparse:     expected void [noderef] __iomem *base
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1228:33: sparse:     got struct epf_ntb_ctrl *reg
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1240:33: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected void [noderef] __iomem *base @@     got struct epf_ntb_ctrl *reg @@
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1240:33: sparse:     expected void [noderef] __iomem *base
   drivers/pci/endpoint/functions/pci-epf-vntb.c:1240:33: sparse:     got struct epf_ntb_ctrl *reg

vim +567 drivers/pci/endpoint/functions/pci-epf-vntb.c

0fe017b7ce1e47 Frank Li 2022-09-06  536  
e35f56bb03304a Frank Li 2022-02-22  537  /**
e35f56bb03304a Frank Li 2022-02-22  538   * epf_ntb_db_bar_init() - Configure Doorbell window BARs
e35f56bb03304a Frank Li 2022-02-22  539   * @ntb: NTB device that facilitates communication between HOST and vHOST
e35f56bb03304a Frank Li 2022-02-22  540   */
e35f56bb03304a Frank Li 2022-02-22  541  static int epf_ntb_db_bar_init(struct epf_ntb *ntb)
e35f56bb03304a Frank Li 2022-02-22  542  {
e35f56bb03304a Frank Li 2022-02-22  543  	const struct pci_epc_features *epc_features;
e35f56bb03304a Frank Li 2022-02-22  544  	u32 align;
e35f56bb03304a Frank Li 2022-02-22  545  	struct device *dev = &ntb->epf->dev;
e35f56bb03304a Frank Li 2022-02-22  546  	int ret;
e35f56bb03304a Frank Li 2022-02-22  547  	struct pci_epf_bar *epf_bar;
e35f56bb03304a Frank Li 2022-02-22  548  	void __iomem *mw_addr;
e35f56bb03304a Frank Li 2022-02-22  549  	enum pci_barno barno;
0fe017b7ce1e47 Frank Li 2022-09-06  550  	size_t size;
e35f56bb03304a Frank Li 2022-02-22  551  
e35f56bb03304a Frank Li 2022-02-22  552  	epc_features = pci_epc_get_features(ntb->epf->epc,
e35f56bb03304a Frank Li 2022-02-22  553  					    ntb->epf->func_no,
e35f56bb03304a Frank Li 2022-02-22  554  					    ntb->epf->vfunc_no);
e35f56bb03304a Frank Li 2022-02-22  555  	align = epc_features->align;
0fe017b7ce1e47 Frank Li 2022-09-06  556  	size = epf_ntb_db_size(ntb);
e35f56bb03304a Frank Li 2022-02-22  557  
e35f56bb03304a Frank Li 2022-02-22  558  	barno = ntb->epf_ntb_bar[BAR_DB];
0fe017b7ce1e47 Frank Li 2022-09-06  559  	epf_bar = &ntb->epf->bar[barno];
e35f56bb03304a Frank Li 2022-02-22  560  
0fe017b7ce1e47 Frank Li 2022-09-06  561  	if (ntb->epf_db_phys) {
0fe017b7ce1e47 Frank Li 2022-09-06  562  		mw_addr = NULL;
0fe017b7ce1e47 Frank Li 2022-09-06  563  		epf_bar->phys_addr = ntb->epf_db_phys;
0fe017b7ce1e47 Frank Li 2022-09-06  564  		epf_bar->barno = barno;
0fe017b7ce1e47 Frank Li 2022-09-06  565  		epf_bar->size = size;
0fe017b7ce1e47 Frank Li 2022-09-06  566  	} else {
e35f56bb03304a Frank Li 2022-02-22 @567  		mw_addr = pci_epf_alloc_space(ntb->epf, size, barno, align, 0);
e35f56bb03304a Frank Li 2022-02-22  568  		if (!mw_addr) {
0fe017b7ce1e47 Frank Li 2022-09-06  569  			dev_err(dev, "Failed to allocate door bell address\n");
e35f56bb03304a Frank Li 2022-02-22  570  			return -ENOMEM;
e35f56bb03304a Frank Li 2022-02-22  571  		}
0fe017b7ce1e47 Frank Li 2022-09-06  572  	}
e35f56bb03304a Frank Li 2022-02-22  573  
e35f56bb03304a Frank Li 2022-02-22  574  	ntb->epf_db = mw_addr;
e35f56bb03304a Frank Li 2022-02-22  575  
e35f56bb03304a Frank Li 2022-02-22  576  	ret = pci_epc_set_bar(ntb->epf->epc, ntb->epf->func_no, ntb->epf->vfunc_no, epf_bar);
e35f56bb03304a Frank Li 2022-02-22  577  	if (ret) {
e35f56bb03304a Frank Li 2022-02-22  578  		dev_err(dev, "Doorbell BAR set failed\n");
e35f56bb03304a Frank Li 2022-02-22  579  			goto err_alloc_peer_mem;
e35f56bb03304a Frank Li 2022-02-22  580  	}
e35f56bb03304a Frank Li 2022-02-22  581  	return ret;
e35f56bb03304a Frank Li 2022-02-22  582  
e35f56bb03304a Frank Li 2022-02-22  583  err_alloc_peer_mem:
e35f56bb03304a Frank Li 2022-02-22  584  	pci_epc_mem_free_addr(ntb->epf->epc, epf_bar->phys_addr, mw_addr, epf_bar->size);
e35f56bb03304a Frank Li 2022-02-22  585  	return -1;
e35f56bb03304a Frank Li 2022-02-22  586  }
e35f56bb03304a Frank Li 2022-02-22  587
Manivannan Sadhasivam Sept. 13, 2022, 5:24 p.m. UTC | #2
On Tue, Sep 06, 2022 at 10:48:56PM -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.
> 
> 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@nxp.com>
> ---
>  drivers/pci/endpoint/functions/pci-epf-vntb.c | 155 +++++++++++++++---
>  1 file changed, 128 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> index 1466dd1904175..426205b980a09 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;
>  
> @@ -136,13 +137,15 @@ struct epf_ntb {
>  
>  	struct epf_ntb_ctrl *reg;
>  
> -	phys_addr_t epf_db_phy;
> +	phys_addr_t epf_db_phys;

This should be part of a separate patch.

>  	void __iomem *epf_db;
>  
>  	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)
> @@ -253,13 +256,15 @@ 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 (readl(ntb->epf_db + i * 4)) {
> -			if (readl(ntb->epf_db + i * 4))
> -				ntb->db |= 1 << (i - 1);
> +	if (!ntb->epf_db_phys) {
> +		for (i = 1; i < ntb->db_count; i++) {
> +			if (readl(ntb->epf_db + i * 4)) {
> +				if (readl(ntb->epf_db + i * 4))

Why are you reading twice? And why cannot you use _relaxed() variant
here and below?

> +					ntb->db |= 1 << (i - 1);
>  
> -			ntb_db_event(&ntb->ntb, i);
> -			writel(0, ntb->epf_db + i * 4);
> +				ntb_db_event(&ntb->ntb, i);
> +				writel(0, ntb->epf_db + i * 4);
> +			}
>  		}
>  	}
>  
> @@ -454,11 +459,9 @@ static int epf_ntb_config_spad_bar_alloc(struct epf_ntb *ntb)
>  	ctrl->num_mws = ntb->num_mws;
>  	ntb->spad_size = spad_size;
>  
> -	ctrl->db_entry_size = 4;
> -
>  	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] = 4 * i;

4 should be defined as a macro of what it represents.

>  	}
>  
>  	return 0;
> @@ -509,6 +512,28 @@ 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 = 4 * ntb->db_count;

Here also.

> +	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
> @@ -522,33 +547,32 @@ static int epf_ntb_db_bar_init(struct epf_ntb *ntb)
>  	struct pci_epf_bar *epf_bar;
>  	void __iomem *mw_addr;
>  	enum pci_barno barno;
> -	size_t size = 4 * ntb->db_count;
> +	size_t size;
>  
>  	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);
> +	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 door bell address\n");

doorbell

> +			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");
> @@ -704,6 +728,82 @@ 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 == 0)

if (!desc->msi_index)

> +		ntb->epf_db_phys = round_down(addr, size);
> +
> +	reg->db_offset[desc->msi_index] = addr - ntb->epf_db_phys;
> +}
> +#endif
> +
> +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;
> +}
> +
> +static void epf_ntb_epc_msi_init(struct epf_ntb *ntb)

Why cannot you guard this whole function with CONFIG_GENERIC_MSI_IRQ_DOMAIN?

> +{
> +	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);
> +
> +#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
> +	if (platform_msi_domain_alloc_irqs(&ntb->epf->dev,
> +		ntb->db_count,
> +		epf_ntb_write_msi_msg)) {
> +		dev_info(dev, "Can't allocate MSI, fall back to poll mode\n");

falling back to polling mode

Should this be dev_err?

> +		return;
> +	}
> +#else
> +	return;
> +#endif
> +	dev_info(dev, "vntb use MSI as doorbell\n");

Using MSI as a doorbell

> +
> +	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,
> +			       "vntb", ntb);

s/vntb/pci_epf_vntb

> +
> +		if (ret) {
> +			dev_err(dev, "devm_request_irq() failure, fall back to poll mode\n");

Failed to request doorbell IRQ! Falling back to polling mode

> +			ntb->epf_db_phys = 0;
> +			break;
> +		}
> +
> +		if (!i)
> +			ntb->msi_virqbase = virq;

A comment here would be helpful

Thanks,
Mani

> +	}
> +}
> +
>  /**
>   * epf_ntb_epc_init() - Initialize NTB interface
>   * @ntb: NTB device that facilitates communication between HOST and vHOST2
> @@ -1299,14 +1399,15 @@ 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
>
diff mbox series

Patch

diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 1466dd1904175..426205b980a09 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;
 
@@ -136,13 +137,15 @@  struct epf_ntb {
 
 	struct epf_ntb_ctrl *reg;
 
-	phys_addr_t epf_db_phy;
+	phys_addr_t epf_db_phys;
 	void __iomem *epf_db;
 
 	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)
@@ -253,13 +256,15 @@  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 (readl(ntb->epf_db + i * 4)) {
-			if (readl(ntb->epf_db + i * 4))
-				ntb->db |= 1 << (i - 1);
+	if (!ntb->epf_db_phys) {
+		for (i = 1; i < ntb->db_count; i++) {
+			if (readl(ntb->epf_db + i * 4)) {
+				if (readl(ntb->epf_db + i * 4))
+					ntb->db |= 1 << (i - 1);
 
-			ntb_db_event(&ntb->ntb, i);
-			writel(0, ntb->epf_db + i * 4);
+				ntb_db_event(&ntb->ntb, i);
+				writel(0, ntb->epf_db + i * 4);
+			}
 		}
 	}
 
@@ -454,11 +459,9 @@  static int epf_ntb_config_spad_bar_alloc(struct epf_ntb *ntb)
 	ctrl->num_mws = ntb->num_mws;
 	ntb->spad_size = spad_size;
 
-	ctrl->db_entry_size = 4;
-
 	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] = 4 * i;
 	}
 
 	return 0;
@@ -509,6 +512,28 @@  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 = 4 * ntb->db_count;
+	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
@@ -522,33 +547,32 @@  static int epf_ntb_db_bar_init(struct epf_ntb *ntb)
 	struct pci_epf_bar *epf_bar;
 	void __iomem *mw_addr;
 	enum pci_barno barno;
-	size_t size = 4 * ntb->db_count;
+	size_t size;
 
 	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);
+	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 door bell 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");
@@ -704,6 +728,82 @@  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 == 0)
+		ntb->epf_db_phys = round_down(addr, size);
+
+	reg->db_offset[desc->msi_index] = addr - ntb->epf_db_phys;
+}
+#endif
+
+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;
+}
+
+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);
+
+#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
+	if (platform_msi_domain_alloc_irqs(&ntb->epf->dev,
+		ntb->db_count,
+		epf_ntb_write_msi_msg)) {
+		dev_info(dev, "Can't allocate MSI, fall back to poll mode\n");
+		return;
+	}
+#else
+	return;
+#endif
+	dev_info(dev, "vntb use MSI as doorbell\n");
+
+	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,
+			       "vntb", ntb);
+
+		if (ret) {
+			dev_err(dev, "devm_request_irq() failure, fall back to poll mode\n");
+			ntb->epf_db_phys = 0;
+			break;
+		}
+
+		if (!i)
+			ntb->msi_virqbase = virq;
+	}
+}
+
 /**
  * epf_ntb_epc_init() - Initialize NTB interface
  * @ntb: NTB device that facilitates communication between HOST and vHOST2
@@ -1299,14 +1399,15 @@  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;