On Wed, Oct 13, 2021 at 11:56:54AM -0500, Brijesh Singh wrote: > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275 > > Commit 85b8eac59b8c5bd9c7eb9afdb64357ce1aa2e803 added support to ensure > that MMIO is only performed against the un-encrypted memory. If MMIO > is performed against encrypted memory, a #GP is raised. > > The AmdSevDxe uses the functions provided by the MemEncryptSevLib to > clear the memory encryption mask from the page table. If the > MemEncryptSevLib is extended to include VmgExitLib then depedency > chain will look like this: > > OvmfPkg/AmdSevDxe/AmdSevDxe.inf > -----> MemEncryptSevLib class > -----> "OvmfPkg/BaseMemEncryptSevLib/DxeMemEncryptSevLib.inf" instance > -----> VmgExitLib class > -----> "OvmfPkg/VmgExitLib" instance > -----> LocalApicLib class > -----> "UefiCpuPkg/BaseXApicX2ApicLib/BaseXApicX2ApicLib.inf" instance > -----> TimerLib class > -----> "OvmfPkg/AcpiTimerLib/DxeAcpiTimerLib.inf" instance > -----> PciLib class > -----> "OvmfPkg/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf" instance > -----> PciExpressLib class > -----> "MdePkg/BasePciExpressLib/BasePciExpressLib.inf" instance > > The LocalApicLib provides a constructor that gets called before the > AmdSevDxe can clear the memory encryption mask from the MMIO regions. > > When running under the Q35 machine type, the call chain looks like this: > > AcpiTimerLibConstructor () [AcpiTimerLib] > PciRead32 () [DxePciLibI440FxQ35] > PciExpressRead32 () [PciExpressLib] > > The PciExpressRead32 () reads the MMIO region. The MMIO regions are not > yet mapped un-encrypted, so the check introduced in the commit > 85b8eac59b8c5bd9c7eb9afdb64357ce1aa2e803 raises a #GP. > > The AmdSevDxe driver does not require the access to the extended PCI > config space. Accessing a normal PCI config space, via IO port should be > sufficent. Use the module-scope override to make the AmdSevDxe use the > BasePciLib instead of BasePciExpressLib so that PciRead32 () uses the > IO ports instead of the extended config space.
Acked-by: Gerd Hoffmann <kra...@redhat.com> -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#81982): https://edk2.groups.io/g/devel/message/81982 Mute This Topic: https://groups.io/mt/86292900/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
