linux-kernel - Re: [PATCH 19/26] x86/tdx: Make pages shared in ioremap()

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Date:   Thu, 23 Dec 2021 22:09:26 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....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: [PATCH 19/26] x86/tdx: Make pages shared in ioremap()

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...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette