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: <Y3Us9wSX9DrWqCyq@zn.tnic>
Date:   Wed, 16 Nov 2022 19:33:27 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Kalra, Ashish" <ashish.kalra@....com>
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 Wed, Nov 16, 2022 at 12:01:11PM -0600, Kalra, Ashish wrote:
> Ok, so i will work on implementing this leaked pages list and put it on a
> sev/snp associated structure.

See __sgx_sanitize_pages() and the poison list there, for an example.

> Also to add here, we will actually get a not-present #PF instead of the RMP
> violation #PF on writing to these leaked pages, as these pages would have
> been removed from the kernel direct map.

So if you do the list and still have the kernel raise a RMP fault for
those pages, traversing that list in the RMP handler to check whether
the page is there on it, should be a lot faster operation than doing the
#PF thing and removing them from the direct map.

And sorry for misleading you about UPM - we were thinking wrong
yesterday.

Thx.

-- 
Regards/Gruss,
    Boris.

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