Re: Reg. Tee init fail...

[Juergen Gross <jgross@xxxxxxxx>]

On 30.06.22 05:32, SK, SivaSangeetha (Siva Sangeetha) wrote:
> [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?
Yes, I think using the DMA interface is the correct way to handle that.

BTW, I did a similar fix for the dcdbas driver recently:

https://lore.kernel.org/r/20220318150950.16843-1-jgross@xxxxxxxx


Juergen

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