linux-kernel - Re: [PATCH] x86: sgx: Don't track poisoned pages for reclaiming

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Message-ID: <CAOq732KGpve688KWFCh1zdrme3vm7GxEiw6UjHswk5h6B3cNDg@mail.gmail.com>
Date: Wed, 12 Feb 2025 01:32:29 +0100
From: andrzej zaborowski <balrogg@...il.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: "Huang, Kai" <kai.huang@...el.com>, Jarkko Sakkinen <jarkko@...nel.org>, x86@...nel.org, 
	linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Tony Luck <tony.luck@...el.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>, 
	"H . Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86: sgx: Don't track poisoned pages for reclaiming

On Wed, 12 Feb 2025 at 00:31, Dave Hansen <dave.hansen@...el.com> wrote:
> On 2/11/25 13:18, Huang, Kai wrote:
> >>> This requires low-level SGX implementation knowledge to fully
> >>> understand. Both what "ETRACK, EBLOCK and EWB" are in the first place,
> >>> how they are involved in reclaim and also why EREMOVE doesn't lead to
> >>> the same fate.
> >>
> >> Does it? [I'll dig up Intel SDM to check this]
> >>
> > I just did. 🙂
> >
> > It seems EREMOVE only reads and updates the EPCM entry for the target
> > EPC page but won't actually access that EPC page.
>
> Actually, now that I think about it even more, why would ETRACK or
> EBLOCK access the page itself? They seem superficially like they'd be
> metadata-only too.

I haven't seen a crash in either of these (always in EWB), I didn't
want to imply that.  But starting that sequence seems wrong knowing we
cannot reclaim the page.

Best regards