linux-kernel - Re: [RFC v2 28/32] x86/tdx: Make pages shared in ioremap()

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Message-ID: <YKgA1od/SqycWWds@zn.tnic>
Date:   Fri, 21 May 2021 20:49:58 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>, linux-kernel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [RFC v2 28/32] x86/tdx: Make pages shared in ioremap()

On Fri, May 21, 2021 at 11:19:15AM -0500, Tom Lendacky wrote:
> In arch/x86/mm/mem_encrypt.c, sme_early_init() (should have renamed that
> when SEV support was added), we do:
> 	if (sev_active())
> 		swiotlb_force = SWIOTLB_FORCE;
> 
> TDX should be able to do a similar thing without having to touch
> arch/x86/kernel/pci-swiotlb.c.
> 
> That would remove any confusion over SME being part of a
> protected_guest_has() call.

Even better.

> I kinda like the separate function, though.

Only if you clean it up and get rid of the inverted logic and drop that
silly switch-case.

> Except mem_encrypt_active() covers both SME and SEV, so
> protected_guest_has() would be confusing.

I don't understand - the AMD-specific function amd_protected_guest_has()
would return sme_me_mask just like mem_encrypt_active() does and we can
get rid of latter.

Or do you have a problem with the name protected_guest_has() containing
"guest" while we're talking about SME here?

If so, feel free to suggest a better one - the name does not have to
have "guest" in it.

Thx.


-- 
Regards/Gruss,
    Boris.

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