Re: [PATCHv2 22/29] x86/tdx: Make pages shared in ioremap()

Tom Lendacky
2022-02-15T15:55:26Z

On 2/15/22 09:41, Kirill A. Shutemov wrote:
> On Tue, Feb 15, 2022 at 08:49:34AM -0600, Tom Lendacky wrote:
>> On 2/14/22 16:09, Kirill A. Shutemov wrote:
>>> On Mon, Feb 07, 2022 at 06:28:04PM +0100, Borislav Petkov wrote:
>>>> On Mon, Feb 07, 2022 at 08:57:39AM -0800, Dave Hansen wrote:
>>>>> We can surely *do* this with cc_something() helpers. It's just not as
>>>>> easy as making cc_set/cc_clear().
>>>>
>>>> Sure, that's easy: cc_pgprot_{enc,dec}() or so.
>>>
>>> So, I've ended up with this in <asm/pgtable.h>
>>>
>>> /*
>>> * Macros to add or remove encryption attribute
>>> */
>>> #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
>>> pgprotval_t cc_enc(pgprotval_t protval);
>>> pgprotval_t cc_dec(pgprotval_t protval);
>>> #define pgprot_encrypted(prot) __pgprot(cc_enc(pgprot_val(prot)))
>>> #define pgprot_decrypted(prot) __pgprot(cc_dec(pgprot_val(prot)))
>>> #else
>>> #define pgprot_encrypted(prot) (prot)
>>> #define pgprot_decrypted(prot) (prot)
>>> #endif
>>
>> A couple of things. I think cc_pgprot_enc() and cc_pgprot_dec() would be
>> more descriptive/better names to use here.
>>
>> Also, can they be defined in include/linux/cc_platform.h (with two versions
>> based on CONFIG_ARCH_HAS_CC_PLATFORM) and have that included here? Or is
>> there some header file include issues when trying to include it? That would
>> clean this block up into just two lines.
>
> Well, pgprotval_t is x86-specific. It cannot be used in generic headers.

Ah, right.

> We can use u64 here instead. It is wider than pgprotval_t on 2-level
> paging x86, but should work.

Hmm..., yeah. Maybe unsigned long? CONFIG_ARCH_HAS_CC_PLATFORM is X86_64
only, so 2-level paging wouldn't be applicable when an unsigned long is
64-bits?

I'll let the maintainers weigh in on that.

>
> But with u64 as type, I'm not sure 'pgprot' in the name is jutified.

Maybe cc_mask_{enc,dec}()? It just sounds like cc_{enc,dec}() is actually
performing encryption or decryption and can be confusing.

Thanks,
Tom

>
> Hm?
>