nvme-cli shows failed to map on Kernel 4.16.16

nvme-cli shows failed to map on Kernel 4.16.16

[Yogi Wannabe]

Hi all,

I downloaded the latest nvme-cli-master and ran the following command
on a Centos 7.4 with kernel 3.19.8. The command worked fine

./nvme list /dev/nvme0n1

I ran the same command on a Debian 9.5 with Kernel 4.16.16 and I got
the error msg "failed to map". Googling led me to this link
https://github.com/linux-nvme/nvme-cli/issues/81

I checked the kernel configuration on 4.16.16 and I see this setting:
CONFIG_IO_STRICT_DEVMEM=y

Does this mean that nvme list won't work until I rebuild the kernel
with CONFIG_IO_STRICT_DEVMEM=n?

thanks

nvme-cli shows failed to map on Kernel 4.16.16

[Keith Busch]

On Wed, Jul 18, 2018@04:08:43PM -0700, Yogi Wannabe wrote:
> Hi all,
> 
> I downloaded the latest nvme-cli-master and ran the following command
> on a Centos 7.4 with kernel 3.19.8. The command worked fine
> 
> ./nvme list /dev/nvme0n1
> 
> I ran the same command on a Debian 9.5 with Kernel 4.16.16 and I got
> the error msg "failed to map". Googling led me to this link
> https://github.com/linux-nvme/nvme-cli/issues/81
> 
> I checked the kernel configuration on 4.16.16 and I see this setting:
> CONFIG_IO_STRICT_DEVMEM=y
> 
> Does this mean that nvme list won't work until I rebuild the kernel
> with CONFIG_IO_STRICT_DEVMEM=n?

That is correct, you will not be able to use that command when
CONFIG_IO_STRICT_DEVMEM=y. When that kernel config option is set, the
kernel will not allow user space to mmap io memory if a driver also
mapped it.

nvme-cli shows failed to map on Kernel 4.16.16

[Christoph Hellwig]

On Wed, Jul 18, 2018@05:12:11PM -0600, Keith Busch wrote:
> That is correct, you will not be able to use that command when
> CONFIG_IO_STRICT_DEVMEM=y. When that kernel config option is set, the
> kernel will not allow user space to mmap io memory if a driver also
> mapped it.

Yikes.  We really ought to have a way to scrape that information
without reading the bar..