Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory

Kirill A. Shutemov
2022-08-09T11:11:48Z

On Sat, Jul 23, 2022 at 01:14:07PM +0200, Ard Biesheuvel wrote:
> On Thu, 21 Jul 2022 at 19:13, Dave Hansen <dave.hansen@intel.com> wrote:
> >
> > On 7/19/22 17:26, Marc Orr wrote:
> > > - Dave's suggestion to "2. Boot some intermediate thing like a
> > > bootloader that does acceptance ..." is pretty clever! So if upstream
> > > thinks this FW-kernel negotiation is not a good direction, maybe we
> > > (Google) can pursue this idea to avoid introducing yet another tag on
> > > our images.
> >
> > I'm obviously speaking only for myself here and not for "upstream" as a
> > whole, but I clearly don't like the FW/kernel negotiation thing. It's a
> > permanent pain in our necks to solve a very temporary problem.
>
> EFI is basically our existing embodiment of this fw/kernel negotiation
> thing, and iff we need it, I have no objection to using it for this
> purpose, i.e., to allow the firmware to infer whether or not it should
> accept all available memory on behalf of the OS before exiting boot
> services. But if we don't need this, even better.

FW/kernel negotiation does not work if there's a boot loader in the middle
that does ExitBootServices(). By the time kernel can announce if it
supports unaccepted memory there's nobody to announce to.

--
Kiryl Shutsemau / Kirill A. Shutemov