UefiCpuPkg/MpInitLib: use BSP to do extended topology check

During AP bringup, just after switching to long mode, APs will do some
cpuid calls to verify that the extended topology leaf (0xB) is available
so they can fetch their x2 APIC IDs from it. In the case of SEV-ES,
these cpuid instructions must be handled by direct use of the GHCB MSR
protocol to fetch the values from the hypervisor, since a #VC handler
is not yet available due to the AP's stack not being set up yet.

For SEV-SNP, rather than relying on the GHCB MSR protocol, it is
expected that these values would be obtained from the SEV-SNP CPUID
table instead. The actual x2 APIC ID (and 8-bit APIC IDs) would still
be fetched from hypervisor using the GHCB MSR protocol however, so
introducing support for the SEV-SNP CPUID table in that part of the AP
bring-up code would only be to handle the checks/validation of the
extended topology leaf.

Rather than introducing all the added complexity needed to handle these
checks via the CPUID table, instead let the BSP do the check in advance,
since it can make use of the #VC handler to avoid the need to scan the
SNP CPUID table directly, and add a flag in ExchangeInfo to communicate
the result of this check to APs.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Ray Ni <ray.ni@intel.com>
Suggested-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h b/UefiCpuPkg/Library/MpInitLib/MpLib.h
index 56de3bfb1c..be67cd88ec 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
@@ -224,6 +224,7 @@ typedef struct {
   BOOLEAN            SevEsIsEnabled;

   BOOLEAN            SevSnpIsEnabled;

   UINTN              GhcbBase;

+  BOOLEAN            ExtTopoAvail;

 } MP_CPU_EXCHANGE_INFO;

 

 #pragma pack()

@@ -788,4 +789,14 @@ ConfidentialComputingGuestHas (
   CONFIDENTIAL_COMPUTING_GUEST_ATTR  Attr

   );

 

+/**

+  The function fills the exchange data for the AP.

+

+  @param[in]   ExchangeInfo  The pointer to CPU Exchange Data structure

+**/

+VOID

+FillExchangeInfoDataSevEs (

+  IN volatile MP_CPU_EXCHANGE_INFO  *ExchangeInfo

+  );

+

 #endif