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

[Tom Lendacky <thomas.lendacky@amd.com>]

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.

Thanks,
Tom

> 
> And cc_platform.c:
> 
> pgprotval_t cc_enc(pgprotval_t protval)
> {
> 	if (sme_me_mask)
> 		return __sme_set(protval);
> 	else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> 		return protval & ~tdx_shared_mask();
> 	else
> 		return protval;
> }
> 
> pgprotval_t cc_dec(pgprotval_t protval)
> {
> 	if (sme_me_mask)
> 		return __sme_clr(protval);
> 	else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> 		return protval | tdx_shared_mask();
> 	else
> 		return protval;
> }
> EXPORT_SYMBOL_GPL(cc_dec);