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

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Date:   Fri, 21 May 2021 16:14:11 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
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 5/21/21 1:49 PM, Borislav Petkov wrote:
> 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?

The latter.

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

Let me see if I can come up with something that will make sense.

Thanks,
Tom

> 
> Thx.
> 
>