Re: [PATCH V2 1/1] MdeModulePkg/Variable: Fix volatile variable RT cache update logic

["Liming Gao" <liming.gao@intel.com>]

Reviewed-by: Liming Gao <liming.gao@intel.com>

>-----Original Message-----
>From: Kubacki, Michael A
>Sent: Wednesday, November 13, 2019 7:41 AM
>To: devel@edk2.groups.io
>Cc: Gao, Liming <liming.gao@intel.com>; Kinney, Michael D
><michael.d.kinney@intel.com>; Wang, Jian J <jian.j.wang@intel.com>; Wu,
>Hao A <hao.a.wu@intel.com>
>Subject: [PATCH V2 1/1] MdeModulePkg/Variable: Fix volatile variable RT
>cache update logic
>
>REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2333
>
>During a SetVariable () invocation, UpdateVariable () is called.
>UpdateVariable () contains logic to determine whether a volatile or
>non-volatile UEFI variable was set so the corresponding runtime
>cache can be updated to reflect the change. The current logic simply
>evaluates Variable->Volatile to determine which runtime cache should
>be updated.
>
>The problem is Variable->Volatile does not always reflect whether a
>volatile variable is being set. Variable->Volatile is set to TRUE
>only in the case a pre-existing variable is found in the volatile
>variable store. Therefore, the value is FALSE when a new volatile
>variable is written.
>
>This change updates the logic to take this into account. If a new
>variable is written successfully, the Attributes will accurately
>reflect whether the variable is non-volatile. If a pre-existing
>variable is modified, the Volatile field will reflect the type of
>variable (Attributes are not reliable; e.g. 0x0 indicates deletion).
>
>* Observable symptom: A volatile variable that was set successfully
>  might return EFI_NOT_FOUND when the variable should be found.
>
>* The issue is a regression introduced to the variable services only
>  when the variable runtime cache is enabled by the following PCD
>  being set to TRUE:
>  gEfiMdeModulePkgTokenSpaceGuid.PcdEnableVariableRuntimeCache
>
>* The issue was implemented in commit aab3b9b9a1 but the PCD was not
>  set to TRUE by default enabling the issue until commit e07b7d024a.
>
>Fixes: aab3b9b9a1e5e1f3fa966fb1667fc3e6c47e7706
>
>Cc: Liming Gao <liming.gao@intel.com>
>Cc: Michael D Kinney <michael.d.kinney@intel.com>
>Cc: Jian J Wang <jian.j.wang@intel.com>
>Cc: Hao A Wu <hao.a.wu@intel.com>
>Signed-off-by: Michael Kubacki <michael.a.kubacki@intel.com>
>---
>
>Notes:
>    V2 changes:
>    * Sets the runtime cache instance pointer that was updated in V1
>      using an if/else statement instead of just an if statement so
>      it better aligns to the original code style.
>    * Updates the commit message to include the simple symptom most
>      commonly observed that this change fixes, an explicit description
>      that this change is a regression to the variable services, that
>      it only is present when the runtime variable cache is enabled, and
>      relevant commit details.
>
> MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
>b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
>index 29d6aca993..b0ee5e50d0 100644
>--- a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
>+++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
>@@ -2296,10 +2296,10 @@ UpdateVariable (
>
> Done:
>   if (!EFI_ERROR (Status)) {
>-    if (Variable->Volatile) {
>-      VolatileCacheInstance = &(mVariableModuleGlobal-
>>VariableGlobal.VariableRuntimeCacheContext.VariableRuntimeVolatileCach
>e);
>-    } else {
>+    if ((Variable->CurrPtr != NULL && !Variable->Volatile) || (Attributes &
>EFI_VARIABLE_NON_VOLATILE) != 0) {
>       VolatileCacheInstance = &(mVariableModuleGlobal-
>>VariableGlobal.VariableRuntimeCacheContext.VariableRuntimeNvCache);
>+    } else {
>+      VolatileCacheInstance = &(mVariableModuleGlobal-
>>VariableGlobal.VariableRuntimeCacheContext.VariableRuntimeVolatileCach
>e);
>     }
>
>     if (VolatileCacheInstance->Store != NULL) {
>--
>2.16.2.windows.1