[PATCH v5 3/8] ACPI/IORT: Add a helper to retrieve RMR memory regions

[Jon Nettleton]

On Wed, May 26, 2021 at 6:36 PM Shameerali Kolothum Thodi
<shameerali.kolothum.thodi at huawei.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Laurentiu Tudor [mailto:laurentiu.tudor at nxp.com]
> > Sent: 26 May 2021 08:53
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi at huawei.com>;
> > linux-arm-kernel at lists.infradead.org; linux-acpi at vger.kernel.org;
> > iommu at lists.linux-foundation.org
> > Cc: jon at solid-run.com; Linuxarm <linuxarm at huawei.com>;
> > steven.price at arm.com; Guohanjun (Hanjun Guo) <guohanjun at huawei.com>;
> > yangyicong <yangyicong at huawei.com>; Sami.Mujawar at arm.com;
> > robin.murphy at arm.com; wanghuiqiang <wanghuiqiang at huawei.com>
> > Subject: Re: [PATCH v5 3/8] ACPI/IORT: Add a helper to retrieve RMR memory
> > regions
> >
> > Hi Shameer,
> >
> > On 5/24/2021 2:02 PM, Shameer Kolothum wrote:
> > > Add a helper function that retrieves RMR memory descriptors
> > > associated with a given IOMMU. This will be used by IOMMU
> > > drivers to setup necessary mappings.
> > >
> > > Now that we have this, invoke it from the generic helper
> > > interface.
> > >
> > > Signed-off-by: Shameer Kolothum
> > <shameerali.kolothum.thodi at huawei.com>
> > > ---
> > >  drivers/acpi/arm64/iort.c | 50
> > +++++++++++++++++++++++++++++++++++++++
> > >  drivers/iommu/dma-iommu.c |  4 ++++
> > >  include/linux/acpi_iort.h |  7 ++++++
> > >  3 files changed, 61 insertions(+)
> > >
> > > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > > index fea1ffaedf3b..01917caf58de 100644
> > > --- a/drivers/acpi/arm64/iort.c
> > > +++ b/drivers/acpi/arm64/iort.c
> > > @@ -12,6 +12,7 @@
> > >
> > >  #include <linux/acpi_iort.h>
> > >  #include <linux/bitfield.h>
> > > +#include <linux/dma-iommu.h>
> > >  #include <linux/iommu.h>
> > >  #include <linux/kernel.h>
> > >  #include <linux/list.h>
> > > @@ -837,6 +838,53 @@ static inline int iort_add_device_replay(struct
> > device *dev)
> > >     return err;
> > >  }
> > >
> > > +/**
> > > + * iort_iommu_get_rmrs - Helper to retrieve RMR info associated with
> > IOMMU
> > > + * @iommu: fwnode for the IOMMU
> > > + * @head: RMR list head to be populated
> > > + *
> > > + * Returns: 0 on success, <0 failure
> > > + */
> > > +int iort_iommu_get_rmrs(struct fwnode_handle *iommu_fwnode,
> > > +                   struct list_head *head)
> > > +{
> > > +   struct iort_rmr_entry *e;
> > > +   struct acpi_iort_node *iommu;
> > > +   int rmrs = 0;
> > > +
> > > +   iommu = iort_get_iort_node(iommu_fwnode);
> > > +   if (!iommu || list_empty(&iort_rmr_list))
> > > +           return -ENODEV;
> > > +
> > > +   list_for_each_entry(e, &iort_rmr_list, list) {
> > > +           int prot = IOMMU_READ | IOMMU_WRITE | IOMMU_NOEXEC |
> > IOMMU_MMIO;
> >
> > We have a case with an IP block that needs EXEC rights on its reserved
> > memory, so could you please drop the IOMMU_NOEXEC flag?
>
> Ok, I think I can drop that one if there are no other concerns. I was not quite
> sure what to include here in the first place as the IORT spec is not giving any
> further details about the RMR regions(May be the flags field can be extended to
> describe these details).

We probably need to bring this back up to the ACPI forums. This is probably
something that should be attached to the memory range node which does have
4 extra reserved bytes.

-Jon

>
> Thanks,
> Shameer
>
>