Re: [edk2-devel] [PATCH 01/16] OvmfPkg/BaseMemEncryptSevLib: Re-organize page state change support

["Gerd Hoffmann" <kraxel@redhat.com>]

On Fri, Jan 26, 2024 at 04:13:00PM -0600, Tom Lendacky wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654
> 
> In preparation for running under an SVSM at VMPL1 or higher (higher
> numerically, lower privilege), re-organize the way a page state change
> is performed in order to free up the GHCB for use by the SVSM support.
> 
> Currently, the page state change logic directly uses the GHCB shared
> buffer to build the page state change structures. However, this will be
> in conflict with the use of the GHCB should an SVSM call be required.
> 
> Instead, use a separate buffer (an area in the workarea during SEC and
> an allocated page during PEI/DXE) to hold the page state change request
> and only update the GHCB shared buffer as needed.

So the idea is that the lowlevel code takes the "page state change
request", then either writes the request to the GHCB when running in
vmpl == 0 (this patch), or submits a SVSM call when running in
vmpl > 0 (somewhere later in this series I guess)?

> Since the information is copied to, and operated on, in the GHCB shared
> buffer this has the added benefit of not requiring to save the start and
> end entries for use when validating the memory during the page state
> change sequence.

The patch is pretty large, I'm not sure it is possible to make it much
smaller though.

> -  i           = 0;
> +  Index       = 0;

That rename can be splitted.  Will be a rather small chunk though.

take care,
  Gerd



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