Re: [RFC Part2 PATCH v3 02/26] crypto: ccp: Add Platform Security Processor (PSP) device support

[Brijesh Singh <brijesh.singh@amd.com>]

Hi Boris,

On 09/07/2017 09:27 AM, Borislav Petkov wrote:

...

> 
> The commit message above reads better to me as the help text than what
> you have here.
> 
> Also, in order to make it easier for the user, I think we'll need a
> CONFIG_AMD_MEM_ENCRYPT_SEV or so and make that depend on CONFIG_KVM_AMD,
> this above and all the other pieces that are needed. Just so that when
> the user builds such a kernel, all is enabled and not her having to go
> look for what else is needed.
> 
> And then put the sev code behind that config option. Depending on how
> ugly it gets...
> 

I will add more detail in the help text. I will look into adding some
depends.

...

>> +
>> +void psp_add_device(struct psp_device *psp)
> 
> That function is needlessly global and should be static, AFAICT.
> 
> Better yet, it is called only once and its body is trivial so you can
> completely get rid of it and meld it into the callsite.
> 

Agreed, will do.

.....

>> +
>> +static struct psp_device *psp_alloc_struct(struct sp_device *sp)
> 
> "psp_alloc()" is enough I guess.
> 

I was trying to adhere to the existing ccp-dev.c function naming
conversion.

....

> 
> static.
> 
> Please audit all your functions in the psp pile and make them static if
> not needed outside of their compilation unit.
> 

Will do.

>> +{
>> +	unsigned int status;
>> +	irqreturn_t ret = IRQ_HANDLED;
>> +	struct psp_device *psp = data;
> 
> Please sort function local variables declaration in a reverse christmas
> tree order:
> 
> 	<type> longest_variable_name;
> 	<type> shorter_var_name;
> 	<type> even_shorter;
> 	<type> i;
> 

Got it, will do


>> +
>> +	/* read the interrupt status */
>> +	status = ioread32(psp->io_regs + PSP_P2CMSG_INTSTS);
>> +
>> +	/* invoke subdevice interrupt handlers */
>> +	if (status) {
>> +		if (psp->sev_irq_handler)
>> +			ret = psp->sev_irq_handler(irq, psp->sev_irq_data);
>> +		if (psp->tee_irq_handler)
>> +			ret = psp->tee_irq_handler(irq, psp->tee_irq_data);
>> +	}
>> +
>> +	/* clear the interrupt status */
>> +	iowrite32(status, psp->io_regs + PSP_P2CMSG_INTSTS);
> 
> We're clearing the status by writing the same value back?!? Shouldn't
> that be:
> 
> 	iowrite32(0, psp->io_regs + PSP_P2CMSG_INTSTS);
> 

Actually the SW should write "1" to clear the bit. To make it clear, I
can use value 1 and add comment.



> Below I see
> 
> 	iowrite32(0xffffffff, psp->io_regs + PSP_P2CMSG_INTSTS);
> 
> which is supposed to clear IRQs. Btw, you can write that:
> 
> 	iowrite32(-1, psp->io_regs + PSP_P2CMSG_INTSTS);
> 

Sure, I will do that

...

...

>> +
>> +	sp_set_psp_master(sp);
> 
> So this function is called only once and declared somewhere else. You
> could simply do here:
> 
>          if (sp->set_psp_master_device)
>                  sp->set_psp_master_device(sp);
> 
> and get rid of one more global function.


Sure I can do that.

....

>> +	/* Enable interrupt */
>> +	dev_dbg(dev, "Enabling interrupts ...\n");
>> +	iowrite32(7, psp->io_regs + PSP_P2CMSG_INTEN);
> 
> Uh, a magic "7"! Exciting!
> 
> I wonder what that means and whether it could be a define with an
> explanatory name instead. Ditto for the other values...
> 


I will try to define some macro instead of hard coded values.

....

>> +
>> +int psp_dev_resume(struct sp_device *sp)
>> +{
>> +	return 0;
>> +}
>> +
>> +int psp_dev_suspend(struct sp_device *sp, pm_message_t state)
>> +{
>> +	return 0;
>> +}
> 
> Those last two are completely useless. Delete them pls.
> 

We don't have any PM support, I agree will delete it.

...

>> +int psp_request_sev_irq(struct psp_device *psp, irq_handler_t handler,
>> +			void *data)
>> +{
>> +	psp->sev_irq_data = data;
>> +	psp->sev_irq_handler = handler;
>> +
>> +	return 0;
>> +}
>> +
>> +int psp_free_sev_irq(struct psp_device *psp, void *data)
>> +{
>> +	if (psp->sev_irq_handler) {
>> +		psp->sev_irq_data = NULL;
>> +		psp->sev_irq_handler = NULL;
>> +	}
>> +
>> +	return 0;
>> +}
> 
> Both void. Please do not return values from functions which are simply
> void functions by design.
> 

thanks, will fix it.

...

>> +int psp_request_sev_irq(struct psp_device *psp, irq_handler_t handler,
>> +			void *data);
>> +int psp_free_sev_irq(struct psp_device *psp, void *data);
>> +
>> +int psp_request_tee_irq(struct psp_device *psp, irq_handler_t handler,
>> +			void *data);
> 
> Let them stick out.

okay

...

> 
>> +int psp_free_tee_irq(struct psp_device *psp, void *data);
>> +
>> +struct psp_device *psp_get_master_device(void);
>> +
>> +extern const struct psp_vdata psp_entry;
>> +
>> +#endif /* __PSP_DEV_H */
>> diff --git a/drivers/crypto/ccp/sp-dev.c b/drivers/crypto/ccp/sp-dev.c
> 
> So this file is called sp-dev and the other psp-dev. Confusing.
> 
> And in general, why isn't the whole thing a single psp-dev and you can
> save yourself all the registering blabla and have a single driver for
> the whole PSP functionality?
> 
> Distros will have to enable everything anyway and the whole CCP/PSP code
> is only a couple of KBs so you can just as well put it all into a single
> driver. Hm.
> 

PSP provides the interface for communicating with SEV and TEE FWs. I choose
to add generic PSP interface first then plug the SEV FW support. The TEE
commands may be totally different from SEV FW commands hence I tried to put
all the SEV specific changes into one place and adhere to current ccp file
naming convention.

At high level, AMD-SP (AMD Secure Processor) (i.e CCP driver) will provide the
support for CCP, SEV and TEE FW commands.


          +--- CCP
          |
AMD-SP --|
          |            +--- SEV
          |            |
          +---- PSP ---*
                       |
                       +---- TEE

-Brijesh