linux-kernel - Re: [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map when adding them to the RMP table

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Message-ID: <336b55f9-c7e6-4ec9-806b-cb3659dbfdc3@intel.com>
Date: Fri, 12 Jan 2024 12:37:31 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Tom Lendacky <thomas.lendacky@....com>, Borislav Petkov <bp@...en8.de>
Cc: Michael Roth <michael.roth@....com>, x86@...nel.org, kvm@...r.kernel.org,
 linux-coco@...ts.linux.dev, linux-mm@...ck.org,
 linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
 tglx@...utronix.de, mingo@...hat.com, jroedel@...e.de, 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, tobin@....com, vbabka@...e.cz, kirill@...temov.name,
 ak@...ux.intel.com, tony.luck@...el.com,
 sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
 jarkko@...nel.org, ashish.kalra@....com, nikunj.dadhania@....com,
 pankaj.gupta@....com, liam.merwick@...cle.com, zhi.a.wang@...el.com,
 Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map
 when adding them to the RMP table

On 1/12/24 12:28, Tom Lendacky wrote:
> I thought there was also a desire to remove the direct map for any pages
> assigned to a guest as private, not just the case that the comment says.
> So updating the comment would probably the best action.

I'm not sure who desires that.

It's sloooooooow to remove things from the direct map.  There's almost
certainly a frequency cutoff where running the whole direct mapping as
4k is better than the cost of mapping/unmapping.

Actually, where _is_ the TLB flushing here?