On 05/25/18 12:54, Marvin H?user wrote: > Good day, > > While I was inspecting CpuS3DataDxe and the modules depending on its > PCD PcdCpuS3DataAddress,
(Side remark: see e.g. the commit message on 92b87f1c8c0b, "OvmfPkg: build CpuS3DataDxe for -D SMM_REQUIRE", 2015-11-30.) > I noticed that DxeRegisterCpuFeaturesLib seemingly has an asserted > dependency on the PCD being ready when it its executed. I did neither > see a Depex entry, nor an event callback ensuring CpuS3DataDxe has > been loaded, neither exposed by CpuS3DataDxe, nor consumed by this > library. > https://github.com/tianocore/edk2/blob/master/UefiCpuPkg/Library/RegisterCpuFeaturesLib/DxeRegisterCpuFeaturesLib.c#L211 "DxeRegisterCpuFeaturesLib.inf" has a depex on "gEdkiiCpuFeaturesSetDoneGuid". No module in the open source edk2 tree produces this protocol GUID, thus I think this library instance is unusable without other, out-of-tree, modules. I assume that one of those modules satisfies the dependency somehow. Note that CpuS3DataDxe is a platform driver [1]; it is possible that the platform that includes DxeRegisterCpuFeaturesLib in a driver *also* includes such a CpuS3DataDxe variant that populates the PCD and then installs gEdkiiCpuFeaturesSetDoneGuid. [1] I suggest reviewing the message of commit bfec5efa56ca ("UefiCpuPkg/CpuS3DataDxe: Add module to initialize ACPI_CPU_DATA for S3", 2015-11-25). In fact, the series that added "DxeRegisterCpuFeaturesLib.inf" (with the depex mentioned above) *also* modified CpuS3DataDxe: see [2] and [3]. [2] 8b371e93f206 ("UefiCpuPkg/CpuS3DataDxe: Consume the existing PcdCpuS3DataAddress", 2017-03-22) [3] "[edk2] [PATCH 00/11] Add CPU features driver" https://bugzilla.tianocore.org/show_bug.cgi?id=421 http://mid.mail-archive.com/20170309083553.6016-1-jeff.fan@intel.com This suggests that there is an out-of-tree module that populates PcdCpuS3DataAddress before *both* CpuS3DataDxe and DxeRegisterCpuFeaturesLib access the PCD. For achieving this kind of ordering, it would be enough for a driver to first populate the PCD, and then install "gEfiMpServiceProtocolGuid", as both "DxeRegisterCpuFeaturesLib.inf" and "CpuS3DataDxe.inf" depend on that. > Is there anything I'm missing that ensures the execution of > CpuS3DataDxe prior to executing the dependent code? If not, should > there be a dummy protocol exposed? PiSmmCpuDxeSmm also retrieves this > PCD, however safely quits when it has not been set. However, this > could cause unexpected behavior when the PCD is set after this code > has been executed. I did not notice any dependency satisfaction > actions here either. The ordering between CpuS3DataDxe and PiSmmCpuDxeSmm is safe; it's orchestrated by Platform BDS. See commit 92b87f1c8c0b above. > Furthermore, not directly related to this dependency issue, the DXE > code obviously does not implement AllocateAcpiCpuData() entirely. More precisely, the DXE code expects AllocateAcpiCpuData() never to be called; i.e., when the common "RegisterCpuFeaturesLib.c" source file is executed in DXE, the expectation is that it never reaches the call to AllocateAcpiCpuData(). > Hence, the if-branch following its call, will either add another layer > of firing ASSERTs, or it will plainly do nothing. Maybe it could be > moved into the current AllocateAcpiCpuData() function and it be > renamed accordingly? > https://github.com/tianocore/edk2/blob/master/UefiCpuPkg/Library/RegisterCpuFeaturesLib/RegisterCpuFeaturesLib.c#L526 Sorry, I don't understand your point -- CpuRegisterTableWriteWorker() is used in both PEI and DXE, and it's implemented for the general case. When it runs in DXE, the expectation is apparently that AllocateAcpiCpuData() will never be needed / reached, hence the ASSERT(FALSE) stub implementation for the latter, in "DxeRegisterCpuFeaturesLib.c". Oh wait, I think you mistyped your point. The "if" that you refer to does not *follow* the call to AllocateAcpiCpuData(). It *precedes* (guards) it. What the "if" follows is the PcdGet64() call, for PcdCpuS3DataAddress. In DXE, that PcdGet64() is expected to return a nonzero value, hence AllocateAcpiCpuData() is never called, and the assertions about the return value of AllocateAcpiCpuData() are irrelevant (unreached). Thanks Laszlo _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
