Re: [Part2 PATCH v5.1 12.1/31] crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support
From: Brijesh Singh
Date: Tue Oct 10 2017 - 11:01:03 EST
On 10/09/2017 10:21 AM, Borislav Petkov wrote:
...
03:00.1 Encryption controller: Advanced Micro Devices, Inc. [AMD] Device
1468
13:00.2 Encryption controller: Advanced Micro Devices, Inc. [AMD] Device
1456
Btw, what do those PCI functions each do? Public PPR doesn't have them
documented.
Looking at the pci_device_id table (sp-pci.c), the devices id 0x1468
provides the support CCP support directly on the x86-side and device id
0x1456 provides the support for both CCP and PSP features through the
AMD Secure Processor (AMD-SP).
Sure, and if you manage all the devices in a single driver, you can
simply keep them all in a linked list or in an array and iterating over
them is trivial.
Because right now you have
1. sp-pci.c::sp_pci_probe() execute upon the PCI device detection
2. at some point, it does sp-dev.c::sp_init() which decides whether CCP or PSP
3. If PSP, it calls pcp-dev.c::psp_dev_init() which gets that
sp->dev_vdata->psp_vdata which is nothing more than a simple offset
0x10500 which is where the PSP io regs are. For example, if this offset
is hardcoded, why are we even passing that vdata? Just set psp->io_regs =
0x10500. No need for all that passing of structs around.
4. and finally, after that *whole* init has been done, you get to do
->set_psp_master_device(sp);
Or, you can save yourself all that jumping through hoops, merge sp-pci.c
and sp-dev.c into a single sp.c and put *everything* sp-related into
it. And then do the whole work of picking hw apart, detection and
configuration in sp_pci_probe() and have helper functions preparing and
configuring the device.
At the end, it adds it to the list of devices sp.c manages and done. You
actually have that list already:
static LIST_HEAD(sp_units);
in sp-dev.c.
You don't need the set_master thing either - you simply set the
sp_dev_master pointer inside sp.c
I was trying to avoid putting PSP/SEV specific changes in sp-dev.*
files. But if sp.c approach is acceptable to the maintainer then I can
work towards merging sp-dev.c and sp-pci.c into sp.c and then add the
PSP/SEV support.
sp_init() can then go and you can replace it with its function body,
deciding whether it is a CCP or PSP and then call the respective
function which is also in sp.c or ccp-dev.c
And then all those separate compilation units and the interfaces between
them disappear - you have only the calls into the PSP and that's it.
Btw, the CCP thing could remain separate initially, I guess, with all
that ccp-* stuff in there.
Yep, if we decide to go with your recommended approach then we should
leave the CCP as-is for now.
I was trying to follow the CCPÂ model -- in which sp-dev.c simply
forwards the call to ccp-dev.c which does the real work.
And you don't really need that - you can do the real work directly in
sp-dev.c or sp.c or whatever.
>> Currently, sev-dev.c contains barebone common code. IMO, keeping all
the PSP private functions and data structure outside the sp-dev.c/.h
is right thing.
By this model probably, but it causes all that init and registration
jump-through-hoops for no real reason. It is basically wasting cycles
and energy.
I'm all for splitting if it makes sense. But right now I don't see much
sense in this - it is basically a bunch of small compilation units
calling each other. And they could be merged into a single sp.c which
does it all in one go, without a lot of blabla.
Additionally, I would like to highlight that if we decide to go with
moving all the PSP functionality in sp-dev.c then we have to add #ifdef
CONFIG_CRYPTO_DEV_SP_PSP because PSP feature depends on X86_66, whereas
the sp-dev.c gets compiled for all architectures (including aarch64,
i386 and x86_64).
That's fine. You can build it on 32-bit but add to the init function
if (IS_ENABLED(CONFIG_X86_32))
return -ENODEV;
and be done with it. No need for the ifdeffery.
OK, i will use IS_ENABLED where applicable.