OvmfPkg/PlatformInitLib: factor out PlatformCpuCountBugCheck()

Move the QEMU v2.7 reset bug check/workaround to a separate function, as
we'll need to detect further issues.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Brown <mcb30@ipxe.org>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Oliver Steffen <osteffen@redhat.com>
Cc: Sebastien Boeuf <sebastien.boeuf@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4250
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20230119110131.91923-2-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Hugely-appreciated-by: Michael Brown <mcb30@ipxe.org>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/OvmfPkg/Library/PlatformInitLib/Platform.c b/OvmfPkg/Library/PlatformInitLib/Platform.c
index 9ab0342fd8c0e81162c345dcc9482467082b3e0e..d1be5c2d79705ee51f28aea052fdbdca1f106230 100644 (file)
--- a/OvmfPkg/Library/PlatformInitLib/Platform.c
+++ b/OvmfPkg/Library/PlatformInitLib/Platform.c
@@ -404,6 +404,61 @@ PlatformMiscInitialization (
   }\r
 }\r
 \r
+/**\r
+  Check for various QEMU bugs concerning CPU numbers.\r
+\r
+  Compensate for those bugs if various conditions are satisfied, by updating a\r
+  suitable subset of the input-output parameters. The function may not return\r
+  (it may hang deliberately), even in RELEASE builds, if the QEMU bug is\r
+  impossible to cover up.\r
+\r
+  @param[in,out] BootCpuCount  On input, the boot CPU count reported by QEMU via\r
+                               fw_cfg (QemuFwCfgItemSmpCpuCount). The caller is\r
+                               responsible for ensuring (BootCpuCount > 0); that\r
+                               is, if QEMU does not provide the boot CPU count\r
+                               via fw_cfg *at all*, then this function must not\r
+                               be called.\r
+\r
+  @param[in,out] Present       On input, the number of present-at-boot CPUs, as\r
+                               reported by QEMU through the modern CPU hotplug\r
+                               register block.\r
+\r
+  @param[in,out] Possible      On input, the number of possible CPUs, as\r
+                               reported by QEMU through the modern CPU hotplug\r
+                               register block.\r
+**/\r
+STATIC\r
+VOID\r
+PlatformCpuCountBugCheck (\r
+  IN OUT UINT16  *BootCpuCount,\r
+  IN OUT UINT32  *Present,\r
+  IN OUT UINT32  *Possible\r
+  )\r
+{\r
+  ASSERT (*BootCpuCount > 0);\r
+\r
+  //\r
+  // Sanity check: fw_cfg and the modern CPU hotplug interface should expose the\r
+  // same boot CPU count.\r
+  //\r
+  if (*BootCpuCount != *Present) {\r
+    DEBUG ((\r
+      DEBUG_WARN,\r
+      "%a: QEMU v2.7 reset bug: BootCpuCount=%d Present=%u\n",\r
+      __FUNCTION__,\r
+      *BootCpuCount,\r
+      *Present\r
+      ));\r
+    //\r
+    // The handling of QemuFwCfgItemSmpCpuCount, across CPU hotplug plus\r
+    // platform reset (including S3), was corrected in QEMU commit e3cadac073a9\r
+    // ("pc: fix FW_CFG_NB_CPUS to account for -device added CPUs", 2016-11-16),\r
+    // part of release v2.8.0.\r
+    //\r
+    *BootCpuCount = (UINT16)*Present;\r
+  }\r
+}\r
+\r
 /**\r
   Fetch the boot CPU count and the possible CPU count from QEMU, and expose\r
   them to UefiCpuPkg modules.\r
@@ -518,8 +573,8 @@ PlatformMaxCpuCountInitialization (
         UINT8  CpuStatus;\r
 \r
         //\r
-        // Read the status of the currently selected CPU. This will help with a\r
-        // sanity check against "BootCpuCount".\r
+        // Read the status of the currently selected CPU. This will help with\r
+        // various CPU count sanity checks.\r
         //\r
         CpuStatus = IoRead8 (CpuHpBase + QEMU_CPUHP_R_CPU_STAT);\r
         if ((CpuStatus & QEMU_CPUHP_STAT_ENABLED) != 0) {\r
@@ -540,27 +595,7 @@ PlatformMaxCpuCountInitialization (
         ASSERT (Selected == Possible || Selected == 0);\r
       } while (Selected > 0);\r
 \r
-      //\r
-      // Sanity check: fw_cfg and the modern CPU hotplug interface should\r
-      // return the same boot CPU count.\r
-      //\r
-      if (BootCpuCount != Present) {\r
-        DEBUG ((\r
-          DEBUG_WARN,\r
-          "%a: QEMU v2.7 reset bug: BootCpuCount=%d "\r
-          "Present=%u\n",\r
-          __FUNCTION__,\r
-          BootCpuCount,\r
-          Present\r
-          ));\r
-        //\r
-        // The handling of QemuFwCfgItemSmpCpuCount, across CPU hotplug plus\r
-        // platform reset (including S3), was corrected in QEMU commit\r
-        // e3cadac073a9 ("pc: fix FW_CFG_NB_CPUS to account for -device added\r
-        // CPUs", 2016-11-16), part of release v2.8.0.\r
-        //\r
-        BootCpuCount = (UINT16)Present;\r
-      }\r
+      PlatformCpuCountBugCheck (&BootCpuCount, &Present, &Possible);\r
 \r
       MaxCpuCount = Possible;\r
     }\r