Re: [PATCH 1/2] Create UV efi_call macros

Matt Fleming
2016-05-17T12:11:22Z

On Mon, 16 May, at 05:58:40PM, Alex Thorlton wrote:
>
> I was simply re-using the efi_call implementation. Boris suggested that
> I re-write this using the efi_call_virt macro, so I just went with that.
> It all seems to work just fine, so I don't see much reason to stray away
> from that implementation. That being said, I'm obviously not a huge fun
> of the code duplication across the macros. I think there's probably a
> way to minimize this, though I haven't quite worked out the best method
> yet (ideas are welcome :)

The reason I'm pressing for details is that we have a related issue
with the EFI thunking code (CONFIG_EFI_MIXED), where the function
pointer we want to call isn't accessible via the EFI System Table, see
efi_thunk().

Well, technically it *is* accessible, you just can't dereference the
services at runtime because the pointers in the tables are not 64-bit.

But the same constraints exist for EFI thunk and UV code; given a
function pointer to execute that isn't in efi.systab, setup the EFI
runtime environment and call a custom ABI function.

I haven't tested this (or thought through all the implications), but
could you look at providing a table (or something) for mapping a
function name to a ptr,func pair, e.g.

thunk_get_time: runtime_services32(get_time), efi64_thunk
thunk_set_time: runtime_services32(set_time), efi64_thunk
...
uv_call_func: efi.uv_systab->function, uv_efi_call_virt

which we could use in arch_efi_call_virt()? That should give us much
less code duplication and hide all this inside arch/x86.