linux-kernel - Re: [PATCH Part2 v6 14/49] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled

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Message-ID: <a7b3ddb5-73ff-0560-1fa5-beb05864feee@amd.com>
Date:   Wed, 16 Nov 2022 13:23:23 -0600
From:   "Kalra, Ashish" <ashish.kalra@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Vlastimil Babka <vbabka@...e.cz>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
        ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org,
        dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com,
        peterz@...radead.org, srinivas.pandruvada@...ux.intel.com,
        rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com,
        michael.roth@....com, kirill@...temov.name, ak@...ux.intel.com,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        dgilbert@...hat.com, jarkko@...nel.org,
        "Kaplan, David" <David.Kaplan@....com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH Part2 v6 14/49] crypto: ccp: Handle the legacy TMR
 allocation when SNP is enabled

On 11/16/2022 1:09 PM, Borislav Petkov wrote:
> On Wed, Nov 16, 2022 at 12:53:36PM -0600, Kalra, Ashish wrote:
>> Actually, these host allocated pages would have already been removed from
>> the kernel direct map,
> 
> And, as I said above, it would be a lot easier to handle any potential
> faults resulting from the host touching them by having it raise a *RMP*
> fault instead of normal *PF* fault where the latter code is a crazy mess.

Just to reiterate here, we won't be getting a *RMP* fault but will 
instead get a normal (not-present) #PF fault when the host touches these 
pages.

Sorry for any confusion about the fault signaled, earlier i mentioned we 
will get a RMP violation #PF, but actually as these pages are also 
removed from the kernel direct-map, therefore, we will get the 
not-present #PF and not the RMP #PF (core will check and signal 
not-present #PF before it performs the RMP checks).

Thanks,
Ashish