[Question] Failed to access the BAR MMIO space of PCI device

[Question] Failed to access the BAR MMIO space of PCI device

[zhengfei]

Hi,

I'm writing a driver for a SR-IOV device on the PCI bus. My architecture is 
a 64-bit X86 of intel Sandy bridge.

In my device driver, I want to configure the device to transfer data to/from 
X86.I get the the device BAR MMIO base address with the command "lspci -s 
04:00.03 -xxx" in the guest os(kvm).
But after I ioremap() that MMIO base address,I failed to access the BAR MMIO 
space in the guest os(kvm).

Is there a function which show mapping between the real PCI address stored in 
the BAR and the emulated address stored in the BAR?

Thanks.

zhengfei

Re: [Question] Failed to access the BAR MMIO space of PCI device

[Alex Williamson]

On Sun, 2013-04-07 at 19:19 +0000, zhengfei wrote:
> Hi,
> 
> I'm writing a driver for a SR-IOV device on the PCI bus. My architecture is 
> a 64-bit X86 of intel Sandy bridge.
> 
> In my device driver, I want to configure the device to transfer data to/from 
> X86.I get the the device BAR MMIO base address with the command "lspci -s 
> 04:00.03 -xxx" in the guest os(kvm).
> But after I ioremap() that MMIO base address,I failed to access the BAR MMIO 
> space in the guest os(kvm).
> 
> Is there a function which show mapping between the real PCI address stored in 
> the BAR and the emulated address stored in the BAR?

Is this a userspace driver or a kernel driver?  I can't figure out why
you would use lspci to get a static BAR address, then use ioremap() to
map it.  If it's a kernel driver, the sequence you want is something
like:

pci_enable_device
pci_request_selected_regions
pci_iomap

Thanks,
Alex

Re: [Question] Failed to access the BAR MMIO space of PCI device

[zhengfei]

Alex Williamson <alex.williamson <at> redhat.com> writes:

> 
> On Sun, 2013-04-07 at 19:19 +0000, zhengfei wrote:
> > Hi,
> > 
> > I'm writing a driver for a SR-IOV device on the PCI bus. My architecture 
is 
> > a 64-bit X86 of intel Sandy bridge.
> > 
> > In my device driver, I want to configure the device to transfer data 
to/from 
> > X86.I get the the device BAR MMIO base address with the command "lspci -
s 
> > 04:00.03 -xxx" in the guest os(kvm).
> > But after I ioremap() that MMIO base address,I failed to access the BAR 
MMIO 
> > space in the guest os(kvm).
> > 
> > Is there a function which show mapping between the real PCI address 
stored in 
> > the BAR and the emulated address stored in the BAR?
> 
> Is this a userspace driver or a kernel driver?  I can't figure out why
> you would use lspci to get a static BAR address, then use ioremap() to
> map it.  If it's a kernel driver, the sequence you want is something
> like:
> 
> pci_enable_device
> pci_request_selected_regions
> pci_iomap
> 
> Thanks,
> Alex
> 
> 

It is a userspace driver on guest os.To be simply,I got the BAR0 
address(gpa) on guest os,but I failed to access real BAR0 MMIO address space 
of the device with the gpa.So what can I do next? and in which source code 
file,could I find the procedure of mapping the real BAR address space（hpa) 
to gpa?

Thanks

Re: [Question] Failed to access the BAR MMIO space of PCI device

[Alex Williamson]

On Thu, 2013-04-11 at 17:15 +0000, zhengfei wrote:
> Alex Williamson <alex.williamson <at> redhat.com> writes:
> 
> > 
> > On Sun, 2013-04-07 at 19:19 +0000, zhengfei wrote:
> > > Hi,
> > > 
> > > I'm writing a driver for a SR-IOV device on the PCI bus. My architecture 
> is 
> > > a 64-bit X86 of intel Sandy bridge.
> > > 
> > > In my device driver, I want to configure the device to transfer data 
> to/from 
> > > X86.I get the the device BAR MMIO base address with the command "lspci -
> s 
> > > 04:00.03 -xxx" in the guest os(kvm).
> > > But after I ioremap() that MMIO base address,I failed to access the BAR 
> MMIO 
> > > space in the guest os(kvm).
> > > 
> > > Is there a function which show mapping between the real PCI address 
> stored in 
> > > the BAR and the emulated address stored in the BAR?
> > 
> > Is this a userspace driver or a kernel driver?  I can't figure out why
> > you would use lspci to get a static BAR address, then use ioremap() to
> > map it.  If it's a kernel driver, the sequence you want is something
> > like:
> > 
> > pci_enable_device
> > pci_request_selected_regions
> > pci_iomap
> > 
> > Thanks,
> > Alex
> > 
> > 
> 
> It is a userspace driver on guest os.To be simply,I got the BAR0 
> address(gpa) on guest os,but I failed to access real BAR0 MMIO address space 
> of the device with the gpa.So what can I do next? and in which source code 
> file,could I find the procedure of mapping the real BAR address space（hpa) 
> to gpa?

The guest doesn't have access to the hpa, nor should it need it.  To map
BAR0 from guest userspace
mmap /sys/bus/pci/devices/xxxx:xx:xx.x/resource0.  Thanks,

Alex

Re: [Question] Failed to access the BAR MMIO space of PCI device

[zhengfei]

Alex Williamson <alex.williamson <at> redhat.com> writes:

> 
> On Thu, 2013-04-11 at 17:15 +0000, zhengfei wrote:
> > Alex Williamson <alex.williamson <at> redhat.com> writes:
> > 
> > > 
> > > On Sun, 2013-04-07 at 19:19 +0000, zhengfei wrote:
> > > > Hi,
> > > > 
> > > > I'm writing a driver for a SR-IOV device on the PCI bus. My 
architecture 
> > is 
> > > > a 64-bit X86 of intel Sandy bridge.
> > > > 
> > > > In my device driver, I want to configure the device to transfer data 
> > to/from 
> > > > X86.I get the the device BAR MMIO base address with the command 
"lspci -
> > s 
> > > > 04:00.03 -xxx" in the guest os(kvm).
> > > > But after I ioremap() that MMIO base address,I failed to access the 
BAR 
> > MMIO 
> > > > space in the guest os(kvm).
> > > > 
> > > > Is there a function which show mapping between the real PCI address 
> > stored in 
> > > > the BAR and the emulated address stored in the BAR?
> > > 
> > 
> > It is a userspace driver on guest os.To be simply,I got the BAR0 
> > address(gpa) on guest os,but I failed to access real BAR0 MMIO address 
space 
> > of the device with the gpa.So what can I do next? and in which source 
code 
> > file,could I find the procedure of mapping the real BAR address 
space（hpa) 
> > to gpa?
> 
> The guest doesn't have access to the hpa, nor should it need it.  To map
> BAR0 from guest userspace
> mmap /sys/bus/pci/devices/xxxx:xx:xx.x/resource0.  Thanks,
> 
> Alex
> 
> 

Yes,I have followed your advice above,but the problem still exists.I doubt 
the address may not be correct gotten by "mmap 
/sys/bus/pci/devices/xxxx:xx:xx.x/resource0",what can I do next to debug? so 
I want to learn ,how do the guest userspace mapping to host BAR0 address 
space.

zhengfei,
Thanks