linux-kernel - Re: [PATCH v3 2/7] x86/sgx: Add infrastructure to identify SGX EPC pages

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Message-ID: <20210730003809.hp3nmqmgyysa45nz@kernel.org>
Date:   Fri, 30 Jul 2021 03:38:09 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Tony Luck <tony.luck@...el.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/7] x86/sgx: Add infrastructure to identify SGX EPC
 pages

On Wed, Jul 28, 2021 at 03:19:46PM -0700, Dave Hansen wrote:
> On 7/28/21 1:46 PM, Tony Luck wrote:
> > Export a function sgx_is_epc_page() that simply reports whether an
> > address is an EPC page for use elsewhere in the kernel.
> 
> It would be really nice to mention why this needs to be exported to
> modules.  I assume it's the error injection driver or something that can
> be built as a module, but this export was a surprise when I saw it.
> 
> It's probably also worth noting that this is a sloooooooow
> implementation compared to the core VM code that does something
> analogous: pfn_to_page().  It's fine for error handling, but we should
> probably have a comment to this effect so that more liberal use doesn't
> creep in anywhere.

You could also create an xarray to track physical EPC address ranges,
and make the query fast.

/Jarkko