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SubjectRe: [PATCH v12 07/13] x86/sgx: data structures for tracking available EPC pages
On Tue, 3 Jul 2018, Randy Dunlap wrote:
> On 07/03/18 12:46, Thomas Gleixner wrote:
> > On Tue, 3 Jul 2018, Jarkko Sakkinen wrote:
> >
> >> SGX has a set of data structures to maintain information about the enclaves
> >> and their security properties. BIOS reserves a fixed size region of
> >> physical memory for these structures by setting Processor Reserved Memory
> >> Range Registers (PRMRR). This memory area is called Enclave Page Cache
> >> (EPC).
> >>
> >> This commit adds a database of EPC banks for kernel to easily access the
>
> what kind of database? How does one query it?
>
> >> diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
> >> index 2130e639ab49..77b2294fcfb0 100644
> >> --- a/arch/x86/include/asm/sgx.h
> >> +++ b/arch/x86/include/asm/sgx.h
>
>
> >> +/**
> >> + * sgx_get_page - pin an EPC page
> >
> > Description starts with an uppercase letter.
>
> How would someone know that? It's not documented anywhere.

It's a short sentence decribing the function and sentences start usually
with uppercase letters, right?

> I happen to disagree with it.

Then we have to agree that we disagree.

> >> +static __init int sgx_page_cache_init(void)
> >> +{
> >> + unsigned long size;
> >> + unsigned int eax;
> >> + unsigned int ebx;
> >> + unsigned int ecx;
> >> + unsigned int edx;
> >> + unsigned long pa;
> >> + int i;
> >> + int ret;
> >
> > Please aggregate the declarations of the same type. No point in wasting all
> > the screen space. And please use 'u32' for ea-dx
> >
> >> +
> >> + for (i = 0; i < SGX_MAX_EPC_BANKS; i++) {
> >> + cpuid_count(SGX_CPUID, i + SGX_CPUID_EPC_BANKS, &eax, &ebx,
> >> + &ecx, &edx);
> >> + if (!(eax & 0xf))
> >> + break;
> >> +
> >> + pa = ((u64)(ebx & 0xfffff) << 32) + (u64)(eax & 0xfffff000);
> >> + size = ((u64)(edx & 0xfffff) << 32) + (u64)(ecx & 0xfffff000);
> >
> > These magic constants should be 'U', using uppercase 'F' and defines. Plus
> > this wants a comment how pa and size are cobbled together from the cpuid
> > regs.
>
> Why the uppercase 'F'?

Makes is more readable IMO, but I'm not religious about that.

Thanks,

tglx

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