Changeset 94465 in vbox

Timestamp:

Apr 5, 2022 11:43:09 AM (3 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

150796

Message:

Devices/EFI: Fix possible triple fault with SMP configurations during reset

During initialization UEFI enumerates the available CPUs by issuing an IPI to all APs
and waiting a fixed amount of time (50ms by default) for all APs to serve the request.
The timeout is far too low for a hypervisor due to host scheduling interference resulting in the
timed wait to expire before the APs could startup. The BSP will then free the wakeup buffer which
the APs use to startup (switching from real mode to the final execution mode) and overwrite it with 0.
This causes the APs to execute garbage when the respective EMTs get finally scheduled causing all sorts
of weird behavior.

Because it is impossible to set a sane upper timeout without causing execessive delay this change
makes the plartform code query the maximum and current number of CPUs present for the guest so
it can exactly wait for the amount of available CPUs without using any fixed timeouts.

(I'm still puzzled why this only happens when the VM is reset and not during startup...)

Location:

trunk/src/VBox/Devices/EFI

Files:

• DevEFI.cpp (modified) (2 diffs)
• DevEFI.h (modified) (1 diff)
• Firmware/OvmfPkg/PlatformPei/Platform.c (modified) (2 diffs)

trunk/src/VBox/Devices/EFI/DevEFI.cpp

@@ -310 +310 @@
         case EFI_INFO_INDEX_VERTICAL_RESOLUTION:
         case EFI_INFO_INDEX_HORIZONTAL_RESOLUTION:
+        case EFI_INFO_INDEX_CPU_COUNT_CURRENT:
+        case EFI_INFO_INDEX_CPU_COUNT_MAX:
             return 4;
         case EFI_INFO_INDEX_BOOT_ARGS:
@@ -413 +415 @@
         case EFI_INFO_INDEX_HORIZONTAL_RESOLUTION:  return efiInfoNextByteU32(pThisCC, pThisCC->u32HorizontalResolution);
         case EFI_INFO_INDEX_VERTICAL_RESOLUTION:    return efiInfoNextByteU32(pThisCC, pThisCC->u32VerticalResolution);
+        case EFI_INFO_INDEX_CPU_COUNT_CURRENT:      return efiInfoNextByteU32(pThisCC, pThisCC->cCpus); /** @todo CPU hotplugging. */
+        case EFI_INFO_INDEX_CPU_COUNT_MAX:          return efiInfoNextByteU32(pThisCC, pThisCC->cCpus);
 
         /* Keep in sync with value in EfiThunk.asm */

trunk/src/VBox/Devices/EFI/DevEFI.h

@@ -73 +73 @@
     EFI_INFO_INDEX_MCFG_SIZE,
     EFI_INFO_INDEX_APIC_MODE,
+    EFI_INFO_INDEX_CPU_COUNT_CURRENT,
+    EFI_INFO_INDEX_CPU_COUNT_MAX,
     EFI_INFO_INDEX_END
 } EfiInfoIndex;

trunk/src/VBox/Devices/EFI/Firmware/OvmfPkg/PlatformPei/Platform.c

@@ -671 +671 @@
   )
 {
+#ifndef VBOX
   UINT16        BootCpuCount;
+#else
+  UINT32        BootCpuCount;
+#endif
   RETURN_STATUS PcdStatus;
 
+#ifndef VBOX
   //
   // Try to fetch the boot CPU count.
@@ -809 +814 @@
     }
   }
+#else
+  GetVmVariable(EFI_INFO_INDEX_CPU_COUNT_CURRENT, &BootCpuCount, sizeof(BootCpuCount));
+  GetVmVariable(EFI_INFO_INDEX_CPU_COUNT_MAX, &mMaxCpuCount, sizeof(mMaxCpuCount));
+#endif
 
   DEBUG ((DEBUG_INFO, "%a: BootCpuCount=%d mMaxCpuCount=%u\n", __FUNCTION__,