Re: [PATCH v11 00/46] SEV-ES guest support

["Laszlo Ersek" <lersek@redhat.com>]

On 07/21/20 23:18, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> This patch series provides support for running EDK2/OVMF under SEV-ES.
> 
> Secure Encrypted Virtualization - Encrypted State (SEV-ES) expands on the
> SEV support to protect the guest register state from the hypervisor. See
> "AMD64 Architecture Programmer's Manual Volume 2: System Programming",
> section "15.35 Encrypted State (SEV-ES)" [1].
> 
> In order to allow a hypervisor to perform functions on behalf of a guest,
> there is architectural support for notifying a guest's operating system
> when certain types of VMEXITs are about to occur. This allows the guest to
> selectively share information with the hypervisor to satisfy the requested
> function. The notification is performed using a new exception, the VMM
> Communication exception (#VC). The information is shared through the
> Guest-Hypervisor Communication Block (GHCB) using the VMGEXIT instruction.
> The GHCB format and the protocol for using it is documented in "SEV-ES
> Guest-Hypervisor Communication Block Standardization" [2].
> 
> The main areas of the EDK2 code that are updated to support SEV-ES are
> around the exception handling support and the AP boot support.
> 
> Exception support is required starting in Sec, continuing through Pei
> and into Dxe in order to handle #VC exceptions that are generated.  Each
> AP requires it's own GHCB page as well as a page to hold values specific
> to that AP.
> 
> AP booting poses some interesting challenges. The INIT-SIPI-SIPI sequence
> is typically used to boot the APs. However, the hypervisor is not allowed
> to update the guest registers. The GHCB document [2] talks about how SMP
> booting under SEV-ES is performed.
> 
> Since the GHCB page must be a shared (unencrypted) page, the processor
> must be running in long mode in order for the guest and hypervisor to
> communicate with each other. As a result, SEV-ES is only supported under
> the X64 architecture.
> 
> [1] https://www.amd.com/system/files/TechDocs/24593.pdf
> [2] https://developer.amd.com/wp-content/resources/56421.pdf
> 
> ---
> 
> These patches are based on commit:
> 9132a31b9c83 ("MdeModulePkg/DxeCorePerformanceLib: Switch to UnicodeStrnToAsciiStrS")
> 
> A version of the tree can be found at:
> https://github.com/AMDESE/ovmf/tree/sev-es-v19
> 
> Cc: Andrew Fish <afish@apple.com>
> Cc: Anthony Perard <anthony.perard@citrix.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Cc: Benjamin You <benjamin.you@intel.com>
> Cc: Dandan Bi <dandan.bi@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Guo Dong <guo.dong@intel.com>
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Julien Grall <julien@xen.org>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Leif Lindholm <leif@nuviainc.com>
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Maurice Ma <maurice.ma@intel.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> 
> Changes since v10:
> - Fix conflicts around GccInline.c file after moving to latest commit
> - Fix conflicts with OVMF PCD values after moving to latest commit

The updates in patch 29 (OvmfPkg: Create a GHCB page for use during Sec
phase) look OK; thanks.

My understanding is that the MdePkg and MdeModulePkg patches remain
needing approval; is that correct?

Thanks!
Laszlo