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SubjectRe: [PATCH 19/26] x86/tdx: Make pages shared in ioremap()
On Thu, Dec 23, 2021 at 10:09:26PM +0100, Borislav Petkov wrote:
> On Thu, Dec 23, 2021 at 11:56:04PM +0300, Kirill A. Shutemov wrote:
> > Except CC_ATTR_MEM_ENCRYPT is true for TDX too, so it will also depend on
> > check order. It is fragile.
>
> So the query you wanna do is:
>
> if (memory encryption in use)
> use mask;
>
> and the mask you use depends on whether it is SEV or TDX. Right?
>
> If so, you can either do a cc_get_mask() function which gives you either
> the SEV or TDX mask or simply do:
>
> if (CC_ATTR_MEM_ENCRYPT) {
> if (CC_ATTR_GUEST_TDX)
> mask = tdx_shared_mask();
> else if (sme_me_mask)
> mask = sme_me_mask;
> }
>
> Yeah, sme_me_mask has become synonymous with the kernel running as a AMD
> confidential guest. I need to think about how to make this cleaner...

Okay. Meanwhile I leave it this way:

pgprot_t pgprot_cc_encrypted(pgprot_t prot)
{
if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
if (cc_platform_has(CC_ATTR_GUEST_TDX))
return __pgprot(pgprot_val(prot) & ~tdx_shared_mask());
else if (sme_me_mask)
return __pgprot(__sme_set(pgprot_val(prot)));
else
WARN_ON_ONCE(1);
}

return prot;
}
EXPORT_SYMBOL_GPL(pgprot_cc_encrypted);

pgprot_t pgprot_cc_decrypted(pgprot_t prot)
{
if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
if (cc_platform_has(CC_ATTR_GUEST_TDX))
return __pgprot(pgprot_val(prot) | tdx_shared_mask());
else if (sme_me_mask)
return __pgprot(__sme_clr(pgprot_val(prot)));
else
WARN_ON_ONCE(1);
}

return prot;
}
EXPORT_SYMBOL_GPL(pgprot_cc_decrypted);

--
Kirill A. Shutemov

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