On Mon, Dec 13, 2021 at 08:56:55PM +0800, Min Xu wrote: > RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429 > > TdxDxe driver is dispatched early in DXE, due to being list in APRIORI. > This module is responsible for below features: > - Sets max logical cpus based on TDINFO > - Sets PCI PCDs based on resource hobs > - Set shared bit in MMIO region > - Relocate Td mailbox and set its address in MADT table. > > 1. Set shared bit in MMIO region > > Qemu allows a ROM device to set to ROMD mode (default) or MMIO mode. > When it is in ROMD mode, the device is mapped to guest memory and > satisfies read access directly. > > In EDK2 Option ROM is treated as MMIO region. So Tdx guest access > Option ROM via TDVMCALL(MMIO). But as explained above, since Qemu set > the Option ROM to ROMD mode, the call of TDVMCALL(MMIO) always return > INVALID_OPERAND. Tdvf then falls back to direct access. This requires > to set the shared bit to corresponding PageTable entry. Otherwise it > triggers GP fault. > > TdxDxe's entry point is the right place to set the shared bit in MMIO > region because Option ROM has not been discoverd yet. > > 2. Relocate Td mailbox and set the new address in MADT Mutiprocessor > Wakeup Table. > > In TDX the guest firmware is designed to publish a multiprocessor-wakeup > structure to let the guest-bootstrap processor wake up guest-application > processors with a mailbox. The mailbox is memory that the guest firmware > can reserve so each guest virtual processor can have the guest OS send > a message to them. The address of the mailbox is recorded in the MADT > table. See [ACPI]. > > TdxDxe registers for protocol notification > (gQemuAcpiTableNotifyProtocolGuid) to call the AlterAcpiTable(), in > which MADT table is altered by the above Mailbox address. The protocol > will be installed in AcpiPlatformDxe when the MADT table provided by > Qemu is ready. This is to maintain the simplicity of the AcpiPlatformDxe. > > AlterAcpiTable is the registered function which traverses the ACPI > table list to find the original MADT from Qemu. After the new MADT is > configured and installed, the original one will be uninstalled. > > [ACPI] https://uefi.org/specs/ACPI/6.4/05_ACPI_Software_Programming_Model > /ACPI_Software_Programming_Model.html#multiprocessor-wakeup-structure > > Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org> > Cc: Jordan Justen <jordan.l.jus...@intel.com> > Cc: Brijesh Singh <brijesh.si...@amd.com> > Cc: Erdem Aktas <erdemak...@google.com> > Cc: James Bottomley <j...@linux.ibm.com> > Cc: Jiewen Yao <jiewen....@intel.com> > Cc: Tom Lendacky <thomas.lenda...@amd.com> > Cc: Gerd Hoffmann <kra...@redhat.com> > Signed-off-by: Min Xu <min.m...@intel.com>
Acked-by: Gerd Hoffmann <kra...@redhat.com> take care, Gerd -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#84880): https://edk2.groups.io/g/devel/message/84880 Mute This Topic: https://groups.io/mt/87696600/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
