diff mbox

[edk2,v2,1/5] OvmfPkg/PlatformPei: create one memory HOB at S3 resume too, for CpuMpPei

Message ID 1468369086-5616-2-git-send-email-lersek@redhat.com
State Superseded
Headers show

Commit Message

Laszlo Ersek July 13, 2016, 12:18 a.m. UTC 
CpuMpPei will have to place the AP startup vector in memory under 1MB. For
this, CpuMpPei borrows memory under 1MB, but it needs a memory resource
descriptor HOB to exist there even on the S3 resume path (see the
GetWakeupBuffer() function). Produce such a HOB as an exception on the S3
resume path.

CpuMpPei is going be dispatched no earlier than PlatformPei, because
CpuMpPei has a depex on gEfiPeiMemoryDiscoveredPpiGuid, and PlatformPei
calls PublishSystemMemory().

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Jeff Fan <jeff.fan@intel.com>

---

Notes:
    v1:
    - CpuMpPei does not honor memory allocation HOBs from other PEIMs at the
      moment:
      <http://thread.gmane.org/gmane.comp.bios.edk2.devel/14049/focus=14175>,
      but that means no direct problem for this patch.
    
      In the longer term, CpuMpPei's GetWakeupBuffer() function should be
      fixed to consider memalloc HOBs:
      <https://github.com/tianocore/edk2/issues/104>.

 OvmfPkg/PlatformPei/MemDetect.c | 24 +++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

-- 
1.8.3.1


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diff mbox

Patch

diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 7991ba29d7aa..d59b461547c5 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -404,7 +404,29 @@  QemuInitializeRam (
   LowerMemorySize = GetSystemMemorySizeBelow4gb ();
   UpperMemorySize = GetSystemMemorySizeAbove4gb ();
 
-  if (mBootMode != BOOT_ON_S3_RESUME) {
+  if (mBootMode == BOOT_ON_S3_RESUME) {
+    //
+    // Create the following memory HOB as an exception on the S3 boot path.
+    //
+    // Normally we'd create memory HOBs only on the normal boot path. However,
+    // CpuMpPei specifically needs such a low-memory HOB on the S3 path as
+    // well, for "borrowing" a subset of it temporarily, for the AP startup
+    // vector.
+    //
+    // CpuMpPei saves the original contents of the borrowed area in permanent
+    // PEI RAM, in a backup buffer allocated with the normal PEI services.
+    // CpuMpPei restores the original contents ("returns" the borrowed area) at
+    // End-of-PEI. End-of-PEI in turn is emitted by S3Resume2Pei before
+    // transfering control to the OS's wakeup vector in the FACS.
+    //
+    // We expect any other PEIMs that "borrow" memory similarly to CpuMpPei to
+    // restore the original contents. Furthermore, we expect all such PEIMs
+    // (CpuMpPei included) to claim the borrowed areas by producing memory
+    // allocation HOBs, and to honor preexistent memory allocation HOBs when
+    // looking for an area to borrow.
+    //
+    AddMemoryRangeHob (0, BASE_512KB + BASE_128KB);
+  } else {
     //
     // Create memory HOBs
     //