Re: [PATCH for-4.14 2/3] xen/arm: Take into account the DMA width when allocating Dom0 memory banks

[Julien Grall <julien@xxxxxxx>]

On 18/05/2020 21:34, Volodymyr Babchuk wrote:
> Hi Julien,
Hi Volodymyr,

Thank you for the review.

> On Mon, 2020-05-18 at 12:30 +0100, Julien Grall wrote:
> > From: Julien Grall <jgrall@xxxxxxxxxx>
> >
> > At the moment, Xen is assuming that all the devices are at least 32-bit
> > DMA capable. However, some SoCs have devices that may be able to access
> > a much restricted range. For instance, the Raspberry PI 4 has devices
> > that can only access the first GB of RAM.
> >
> > The function arch_get_dma_bit_size() will return the lowest DMA width on
> > the platform. Use it to decide what is the limit for the low memory.
> >
> > Signed-off-by: Julien GralL <jgrall@xxxxxxxxxx>
> > ---
> >   xen/arch/arm/domain_build.c | 32 +++++++++++++++++++-------------
> >   1 file changed, 19 insertions(+), 13 deletions(-)
> >
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index 430708753642..abc4e463d27c 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -211,10 +211,13 @@ fail:
> >    *    the ramdisk and DTB must be placed within a certain proximity of
> >    *    the kernel within RAM.
> >    * 3. For dom0 we want to place as much of the RAM as we reasonably can
> > - *    below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit)
> > + *    below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit).
> Is full stop really needed there?
I was meant to remove the line below as it is now part of 4). I will 
remove it in the next version.
Best regards,

--
Julien Grall