From: "Ard Biesheuvel" <ardb@kernel.org>
To: Nhi Pham <nhi@os.amperecomputing.com>
Cc: Laszlo Ersek <lersek@redhat.com>,
"Andrew (EFI) Fish" <afish@apple.com>,
edk2-devel-groups-io <devel@edk2.groups.io>,
"ardb+tianocore@kernel.org" <ardb+tianocore@kernel.org>
Subject: Re: [edk2-devel] Memory Attribute for depex section
Date: Mon, 15 Jan 2024 15:04:43 +0100 [thread overview]
Message-ID: <CAMj1kXGL8G6awADez4QTKjBa+CW-Q8QrCY4iFf6g7C5d-RrTgw@mail.gmail.com> (raw)
In-Reply-To: <0e0b2e56-30dd-4f5f-9708-98690246efda@os.amperecomputing.com>
On Mon, 15 Jan 2024 at 14:07, Nhi Pham <nhi@os.amperecomputing.com> wrote:
>
> On 1/12/2024 4:45 PM, Laszlo Ersek wrote:
> > (Independently: I think that's a valid thing to do for *SMM* drivers,
> > because the entry point functions of those drivers are permitted to use
> > both SMM and DXE/UEFI protocols. But whether the same is valid for the
> > *standalone* MM drivers -- that looks questionable. Standalone MM
> > drivers should not depend on UEFI/DXE protocols ever, IIUC.)
> >
> >> 3) The issue is patching the grammar in place, why can’t we just make a
> >> copy for the dispatcher grammer, and operate on the copy. Maybe via a
> >> copy on 1st update strategy?
> >
> > Yes, copying the depex to the heap, and patching it there, was Nhi's #1
> > fix proposal. I think that could be made work. But I'm not sure if the
> > perf savings are worth the additional complexity. The heap allocation
> > (where the writeable depex would exist) would have to be permanently
> > associated with the loaded PE image -- because the dispatcher might need
> > to reevaluate the depex across multiple rounds of dispatching. So that's
> > a new field in some image-related structure, it also needs to be freed
> > upon unload (?), what if the memory allocation fails during depex eval
> > (just consider the depex to eval to FALSE?), etc. Doable, but hairy; not
> > sure if the perf is worth that effort.
> >
>
> Thanks so much, Laszlo for your valuable insights.
>
> The approach #1 works for me. I will do further check for your concerns
> above.
>
> I'm trying your suggested patch and investigating the performance being
> discussed here.
>
Not sure what approach #1 means, but I'd prefer to just remove this
optimization from standalone MM, given that not only a) it shouldn't
have to deal with a large number of protocol GUIDs, but also b) the
driver dispatch is much more straight-forward. (Typically, StMM
drivers can be dispatched in the order they appear in the firmware
volume, in which case each DEPEX is evaluated only once anyway)
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next prev parent reply other threads:[~2024-01-16 6:05 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-08 10:11 [edk2-devel] Memory Attribute for depex section Nhi Pham via groups.io
2024-01-10 0:48 ` Nhi Pham via groups.io
2024-01-10 13:09 ` Laszlo Ersek
2024-01-10 13:45 ` Laszlo Ersek
2024-01-10 21:50 ` Pedro Falcato
2024-01-11 8:46 ` Laszlo Ersek
2024-01-11 11:03 ` Laszlo Ersek
2024-01-12 2:10 ` Pedro Falcato
2024-01-12 9:35 ` Laszlo Ersek
2024-01-12 14:46 ` Pedro Falcato
2024-01-12 16:37 ` Michael D Kinney
2024-01-12 18:56 ` Andrew Fish via groups.io
2024-01-12 19:04 ` Michael D Kinney
2024-01-12 19:26 ` Andrew Fish via groups.io
2024-01-12 18:50 ` Andrew Fish via groups.io
2024-01-12 2:44 ` Andrew Fish via groups.io
2024-01-12 9:45 ` Laszlo Ersek
2024-01-15 13:07 ` Nhi Pham via groups.io
2024-01-15 14:04 ` Ard Biesheuvel [this message]
2024-01-15 19:00 ` Laszlo Ersek
2024-01-18 6:00 ` Nhi Pham via groups.io
2024-01-18 14:49 ` Laszlo Ersek
2024-01-19 4:43 ` Nhi Pham via groups.io
2024-01-19 13:54 ` Laszlo Ersek
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