RE: Reg. Tee init fail...

["SK, SivaSangeetha (Siva Sangeetha)" <SivaSangeetha.SK@xxxxxxx>]

[AMD Official Use Only - General]

+team

-----Original Message-----
From: Stefano Stabellini <sstabellini@xxxxxxxxxx> 
Sent: Thursday, June 30, 2022 1:34 AM
To: Julien Grall <julien@xxxxxxx>
Cc: SK, SivaSangeetha (Siva Sangeetha) <SivaSangeetha.SK@xxxxxxx>; 
xen-devel@xxxxxxxxxxxxxxxxxxxx; Stefano Stabellini <sstabellini@xxxxxxxxxx>; 
Bertrand Marquis <bertrand.marquis@xxxxxxx>; Volodymyr Babchuk 
<Volodymyr_Babchuk@xxxxxxxx>; jgross@xxxxxxxx; boris.ostrovsky@xxxxxxxxxx
Subject: Re: Reg. Tee init fail...

Adding Juergen and Boris because this is a Linux/x86 issue.


As you can see from this Linux driver:
https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Flatest%2Fsource%2Fdrivers%2Fcrypto%2Fccp%2Ftee-dev.c%23L132&amp;data=05%7C01%7CSivaSangeetha.SK%40amd.com%7Ce962a907794f4917a80b08da5a0a7b3b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637921298315828104%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=NxmMUckiDRGLv3qLJrhZKBt2zNTuomEZqYJdV74tXxA%3D&amp;reserved=0

Linux as dom0 on x86 is trying to communicate with firmware (TEE). Linux is 
calling __pa to pass a physical address to firmware. However, __pa returns a 
"fake" address not an mfn. I imagine that a quick workaround would be to call 
"virt_to_machine" instead of "__pa" in tee-dev.c.

Normally, if this was a device, the "right fix" would be to use 
swiotlb-xen:xen_swiotlb_map_page to get back a real physical address.

However, xen_swiotlb_map_page is meant to be used as part of the dma_ops API 
and takes a struct device *dev as input parameter. Maybe xen_swiotlb_map_page 
can be used for tee-dev as well?


Basically tee-dev would need to call dma_map_page before passing addresses to 
firmware, and dma_unmap_page when it is done. E.g.:


  cmd_buffer = dma_map_page(dev, virt_to_page(cmd),
                            cmd & ~PAGE_MASK,
                            ring_size,
                            DMA_TO_DEVICE);


Juergen, Boris,
what do you think?



On Fri, 24 Jun 2022, Julien Grall wrote:
> Hi,
> 
> (moving the discussion to xen-devel as I think it is more appropriate)
> 
> On 24/06/2022 10:53, SK, SivaSangeetha (Siva Sangeetha) wrote:
> > [AMD Official Use Only - General]
> 
> Not clear what this means.
> 
> > 
> > Hi Xen team,
> > 
> > In TEE driver, We allocate a ring buffer, get its physical address 
> > from
> > __pa() macro, pass the physical address to secure processor for 
> > mapping it and using in secure processor side.
> > 
> > Source:
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fel
> > ixir.bootlin.com%2Flinux%2Flatest%2Fsource%2Fdrivers%2Fcrypto%2Fccp%
> > 2Ftee-dev.c%23L132&amp;data=05%7C01%7CSivaSangeetha.SK%40amd.com%7Ce
> > 962a907794f4917a80b08da5a0a7b3b%7C3dd8961fe4884e608e11a82d994e183d%7
> > C0%7C0%7C637921298315828104%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAw
> > MDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&a
> > mp;sdata=NxmMUckiDRGLv3qLJrhZKBt2zNTuomEZqYJdV74tXxA%3D&amp;reserved
> > =0
> > 
> > This works good natively in Dom0 on the target.
> > When we boot the same Dom0 kernel, with Xen hypervisor enabled, ring 
> > init fails.
> 
> Do you have any error message or error code?
> 
> > 
> > 
> > We suspect that the address passed to secure processor, is not same 
> > when xen is enabled, and when xen is enabled, some level of address 
> > translation might be required to get exact physical address.
> 
> If you are using Xen upstream, Dom0 will be mapped with IPA == PA. So 
> there should be no need for translation.
> 
> Can you provide more details on your setup (version of Xen, Linux...)?
> 
> Cheers,
> 
> --
> Julien Grall
>