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

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Date:   Tue, 15 Feb 2022 01:09:26 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Dave Hansen <dave.hansen@...el.com>, tglx@...utronix.de,
        mingo@...hat.com, luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 22/29] x86/tdx: Make pages shared in ioremap()

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

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);
-- 
 Kirill A. Shutemov