reserve memory

reserve memory

[Ran Shalit]

Hello,

When doing :
echo 1 > /sys/bus/pci/rescan

Does it results in memory allocation for the new added device ?

Is it that by adding "pci=hpmemsize" we can reserve the memory for the
hot-plug device ? ( So, that there is no dynamic allocation in runtime
)

Thank you,
ranran

Re: reserve memory

[Greg KH]

On Mon, Jul 16, 2018 at 03:41:05PM +0300, Ran Shalit wrote:
> Hello,
> 
> When doing :
> echo 1 > /sys/bus/pci/rescan

Eeek, don't do that unless you _REALLY_ have no other option.

> Does it results in memory allocation for the new added device ?

It depends.  It depends in your platform and what you mean exactly by
"memory allocation".

> Is it that by adding "pci=hpmemsize" we can reserve the memory for the
> hot-plug device ? ( So, that there is no dynamic allocation in runtime
> )

I don't know, you should ask this on the linux-pci mailing list as that
is where the developers who added this are at.

good luck!

greg k-h

Re: reserve memory

[Ran Shalit]

On Mon, Jul 16, 2018 at 8:48 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Mon, Jul 16, 2018 at 03:41:05PM +0300, Ran Shalit wrote:
>> Hello,
>>
>> When doing :
>> echo 1 > /sys/bus/pci/rescan
>
> Eeek, don't do that unless you _REALLY_ have no other option.
>
Hi,

What are the alternatives  ?
I haven't find any information of this issue of memory allocation and
rescan, so any pointer will help,

Thanks,
ranran



>> Does it results in memory allocation for the new added device ?
>
> It depends.  It depends in your platform and what you mean exactly by
> "memory allocation".
>
>> Is it that by adding "pci=hpmemsize" we can reserve the memory for the
>> hot-plug device ? ( So, that there is no dynamic allocation in runtime
>> )
>
> I don't know, you should ask this on the linux-pci mailing list as that
> is where the developers who added this are at.
>
> good luck!
>
> greg k-h

Re: reserve memory

[Greg KH]

On Tue, Jul 17, 2018 at 08:15:24AM +0300, Ran Shalit wrote:
> On Mon, Jul 16, 2018 at 8:48 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Mon, Jul 16, 2018 at 03:41:05PM +0300, Ran Shalit wrote:
> >> Hello,
> >>
> >> When doing :
> >> echo 1 > /sys/bus/pci/rescan
> >
> > Eeek, don't do that unless you _REALLY_ have no other option.
> >
> Hi,
> 
> What are the alternatives  ?

Using real PCI hotplug hardware.  This is a hack that forces the kernel
to rescan the bus because it was not told it needed to do it.  Because
it was not told that, this implies your hardware is not really a pci
hotplug system.

> I haven't find any information of this issue of memory allocation and
> rescan, so any pointer will help,

Why do you feel you need to do the above?  Why isn't your hardware "just
working" when you add/remove a new PCI device?

thanks,

greg k-h