Re: [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation

["Wu, Hao A" <hao.a.wu@intel.com>]

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Hello Ashish,

I think the IOMMU feature is added for the protection of FW integrity against
HW devices, which is the motivation to use IOMMU PPI for memory allocation.

The fix is easy for the DXE part since the IOMMU part has been integrated to the
implementation of the PciIo protocol.

As for the XhciPei case, my thought is that a new helper function (maybe called
'IoMmuAllocateAlignedBuffer') can be added in DmaMem.c file. The main differece
between IoMmuAllocateAlignedBuffer() and existing IoMmuAllocateBuffer() will be:

1. If IOMMU PPI exists, mIoMmu->AllocateBuffer() should be called with bigger
number of pages for alignment and mIoMmu->FreeBuffer() can be called right after
to free the unused pages.

2. If IOMMU PPI does not exist, this case will fall back to a similar fix for
the DXE case.

Ideally, IoMmuFreeBuffer() can be reused to free the aligned buffer.
Please help to raise if you observe any open for the above proposal, thanks.

Best Regards,
Hao Wu

From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On Behalf Of Ashish Singhal
Sent: Friday, October 11, 2019 11:30 AM
To: Wu, Hao A; devel@edk2.groups.io; Ni, Ray
Subject: Re: [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation

Hello Hao,

What is your motivation towards using IoMMUPei for memory allocation now instead of Pei Services? The fix would be simple if we just change the number of pages needed to accommodate for the alignment. The call to free the pages would not do anything.

If we use IoMMUPei, we may need to change function definition for allocate to return how many pages were allocated for each call so that freeing can be done correctly as well. This may need more refactoring of the code that initially thought of.

Thanks
Ashish

From: Wu, Hao A <hao.a.wu@intel.com>
Sent: Thursday, October 10, 2019 9:00 PM
To: devel@edk2.groups.io; Ashish Singhal <ashishsingha@nvidia.com>; Ni, Ray <ray.ni@intel.com>
Subject: RE: [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation

Thanks Ashish,

Please help to send out the fix for XhciPei in a separate patch as well.
I can help to see if verification can be done on my side.

Best Regards,
Hao Wu

From: devel@edk2.groups.io<mailto:devel@edk2.groups.io> [mailto:devel@edk2.groups.io] On Behalf Of Ashish Singhal
Sent: Friday, October 11, 2019 1:51 AM
To: Wu, Hao A; devel@edk2.groups.io<mailto:devel@edk2.groups.io>; Ni, Ray
Subject: Re: [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation

Hello Hao,

I agree that for completeness we should fix the issue in both DXE as well as PEI but on my target, we do not have any PEI phase for me to be able to verify any change that I will be making. If you still want, I can still make the change so that someone else can verify or we can have someone else fix PEI and push my change meanwhile to fix the issue in DXE.

Thanks
Ashish
________________________________
From: Wu, Hao A <hao.a.wu@intel.com<mailto:hao.a.wu@intel.com>>
Sent: Wednesday, October 9, 2019 8:09 PM
To: Ashish Singhal <ashishsingha@nvidia.com<mailto:ashishsingha@nvidia.com>>; devel@edk2.groups.io<mailto:devel@edk2.groups.io> <devel@edk2.groups.io<mailto:devel@edk2.groups.io>>; Ni, Ray <ray.ni@intel.com<mailto:ray.ni@intel.com>>
Subject: RE: [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation

> -----Original Message-----
> From: Ashish Singhal [mailto:ashishsingha@nvidia.com]
> Sent: Thursday, October 10, 2019 9:58 AM
> To: Wu, Hao A; devel@edk2.groups.io<mailto:devel@edk2.groups.io>; Ni, Ray
> Subject: RE: [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation
>
> Hello Hao,
>
> I can see that the PEI also has the same issue and take a look at that as well
> but I have no way to verify that as we are not using it. For the change I have
> made in DXE, I have verified it with an alignment of 4K and 64K.


Is it possible for you to verify the PEI case with a test PEI module that
performs read operation to a USB storage device? I think this will trigger
the affecting codes.

In my opinion, it would be better for the fix to be complete.

Best Regards,
Hao Wu


>
> Thanks
> Ashish
>
> -----Original Message-----
> From: Wu, Hao A <hao.a.wu@intel.com<mailto:hao.a.wu@intel.com>>
> Sent: Wednesday, October 9, 2019 7:33 PM
> To: Ashish Singhal <ashishsingha@nvidia.com<mailto:ashishsingha@nvidia.com>>; devel@edk2.groups.io<mailto:devel@edk2.groups.io>; Ni,
> Ray <ray.ni@intel.com<mailto:ray.ni@intel.com>>
> Subject: RE: [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation
>
> > -----Original Message-----
> > From: Ashish Singhal [mailto:ashishsingha@nvidia.com]
> > Sent: Thursday, October 10, 2019 1:02 AM
> > To: devel@edk2.groups.io<mailto:devel@edk2.groups.io>; Wu, Hao A; Ni, Ray
> > Cc: Ashish Singhal
> > Subject: [PATCH] MdeModulePkg/XhciDxe: Fix Aligned Page Allocation
> >
> > While allocating pages aligned at an alignment higher than 4K,
> > allocate memory taking into consideration the padding required for
> > that alignment. The calls to free pages takes care of this already.
> >
> > Signed-off-by: Ashish Singhal <ashishsingha@nvidia.com<mailto:ashishsingha@nvidia.com>>
> > ---
> >  MdeModulePkg/Bus/Pci/XhciDxe/UsbHcMem.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/MdeModulePkg/Bus/Pci/XhciDxe/UsbHcMem.c
> > b/MdeModulePkg/Bus/Pci/XhciDxe/UsbHcMem.c
> > index fd79988..aa69c47 100644
> > --- a/MdeModulePkg/Bus/Pci/XhciDxe/UsbHcMem.c
> > +++ b/MdeModulePkg/Bus/Pci/XhciDxe/UsbHcMem.c
> > @@ -656,7 +656,7 @@ UsbHcAllocateAlignedPages (
> >                        PciIo,
> >                        AllocateAnyPages,
> >                        EfiBootServicesData,
> > -                      Pages,
> > +                      RealPages,
> >                        &Memory,
> >                        0
> >                        );
>
>
> Hello,
>
> The change looks good to me.
>
> Just a couple of things to confirm:
>
> 1. I think there is a similar case within the XhciPei driver Could you help to
> resolve it as well?
>
> I think for the PEI counterpart you may need to update both
> UsbHcAllocateAlignedPages() and UsbHcFreeAlignedPages(), since the
> IOMMU helper functions like IoMmuAllocateBuffer() and IoMmuFreeBuffer()
> might not be suitable now. Instead, I think services in the IoMmu PPI can be
> used.
>
> 2. Could you help to provide the information on what test has been done for
> the proposed patch?
>
> Thanks in advance.
>
> Best Regards,
> Hao Wu
>
>
> > --
> > 2.7.4
>
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