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

[Gary R Hook]

On 09/07/2017 05:19 PM, Brijesh Singh wrote:
> 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.

I would prefer that we not shorten this. The prior incarnation,
ccp_alloc_struct(), has/had been around for a while. And there are a 
number of
similarly named allocation functions in the driver that we like to keep 
sorted.
If anything, it should be more explanatory, IMO.

> ....
>
> > 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