linux-kernel - Re: [PATCH] x86/cpu/amd: Remove dead code for TSEG region remapping

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Message-ID: <20201202181008.GI2951@zn.tnic>
Date:   Wed, 2 Dec 2020 19:10:08 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>, x86@...nel.org,
        Kim Phillips <kim.phillips@....com>,
        Yazen Ghannam <yazen.ghannam@....com>, Pu Wen <puwen@...on.cn>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/cpu/amd: Remove dead code for TSEG region remapping

On Wed, Dec 02, 2020 at 11:58:15AM -0600, Tom Lendacky wrote:
> I believe this is geared towards performance. If the TSEG base address is
> not 2MB aligned, then hardware has to break down a 2MB TLB entry if the OS
> references the memory within the 2MB page that is before the TSEG base
> address. This can occur whenever the 2MB TLB entry is re-installed because
> of TLB flushes, etc.

And if this gets reinstated properly, then that explanation belongs over
it because nothing else explains what that thing did. So thanks for
digging it out.

-- 
Regards/Gruss,
    Boris.

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