Re: [PATCH] MdeModulePkg/PciHostBridge: Update Mem and PMem Limit Checks

["Wasim Khan" <wasim.khan@nxp.com>]

> -----Original Message-----
> From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Sent: Friday, April 24, 2020 12:27 AM
> To: Wasim Khan <wasim.khan@nxp.com>
> Cc: edk2-devel-groups-io <devel@edk2.groups.io>; Varun Sethi
> <V.Sethi@nxp.com>; Wu, Hao A <hao.a.wu@intel.com>; Ni, Ray
> <ray.ni@intel.com>
> Subject: Re: [PATCH] MdeModulePkg/PciHostBridge: Update Mem and PMem
> Limit Checks
> 
> On Thu, 23 Apr 2020 at 12:43, Wasim Khan <wasim.khan@nxp.com> wrote:
> >
> > With Address Translation Support, it is possible and also correct that
> > Mem and Pmem Limit cross the 4GB boundary.
> > Update the checks so that Mem/PMem Limit should not cross 4GB from the
> > Mem/PMem Base address.
> >
> > Signed-off-by: Wasim Khan <wasim.khan@nxp.com>
> > ---
> >  MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> > b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> > index d304fae..9cf7e98 100644
> > --- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> > +++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> > @@ -117,8 +117,8 @@ CreateRootBridge (
> >    // Make sure Mem and MemAbove4G apertures are valid
> >    //
> >    if (RESOURCE_VALID (&Bridge->Mem)) {
> > -    ASSERT (Bridge->Mem.Limit < SIZE_4GB);
> > -    if (Bridge->Mem.Limit >= SIZE_4GB) {
> > +    ASSERT (Bridge->Mem.Limit < (Bridge->Mem.Base + SIZE_4GB));
> > +    if (Bridge->Mem.Limit >= (Bridge->Mem.Base + SIZE_4GB)) {
> >        return NULL;
> >      }
> >    }
> > @@ -129,8 +129,8 @@ CreateRootBridge (
> >      }
> >    }
> >    if (RESOURCE_VALID (&Bridge->PMem)) {
> > -    ASSERT (Bridge->PMem.Limit < SIZE_4GB);
> > -    if (Bridge->PMem.Limit >= SIZE_4GB) {
> > +    ASSERT (Bridge->PMem.Limit < (Bridge->PMem.Base + SIZE_4GB));
> > +    if (Bridge->PMem.Limit >= (Bridge->PMem.Base + SIZE_4GB)) {
> >        return NULL;
> >      }
> >    }
> > --
> > 2.7.4
> >
> 
> This is not the right fix.
> 
> The translation offset should be taken into account for these checks

Thanks for the review Ard. 
device address = host address + translation offset.
Mem and Pmem represents "device address" , so that are already taking translation offset into account.