Reviewed-by: Michael Kinney <michael.d.kin...@intel.com>
>-----Original Message----- >From: Laszlo Ersek [mailto:ler...@redhat.com] >Sent: Tuesday, November 03, 2015 1:01 PM >To: edk2-de...@ml01.01.org >Cc: Paolo Bonzini; Justen, Jordan L; Kinney, Michael D >Subject: [PATCH v4 25/41] OvmfPkg: any AP in SMM should not wait for the >BSP for more than 100 ms > >This patch complements the previous one, "OvmfPkg: use relaxed AP SMM >synchronization mode". While that patch focuses on the case when the SMI >is raised synchronously by the BSP, on the BSP: > > BSPHandler() [UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c] > SmmWaitForApArrival() [UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c] > IsSyncTimerTimeout() [UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c] > >this patch concerns itself with the case when it is one of the APs that >raises (and sees delivered) the synchronous SMI: > > APHandler() [UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c] > IsSyncTimerTimeout() [UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c] > >Namely, in APHandler() the AP waits for the BSP to enter SMM regardless of >PcdCpuSmmSyncMode, for PcdCpuSmmApSyncTimeout microseconds (the >default >value is 1 second). If the BSP doesn't show up in SMM within that >interval, then the AP brings it in with a directed SMI, and waits for the >BSP again for PcdCpuSmmApSyncTimeout microseconds. > >Although during boot services, SmmControl2DxeTrigger() is only called by >the BSP, at runtime the OS can invoke runtime services from an AP (it can >even be forced with "taskset -c 1 efibootmgr"). Because on QEMU >SmmControl2DxeTrigger() only raises the SMI for the calling processor (BSP >and AP alike), the first interval above times out invariably in such cases >-- the BSP never shows up before the AP calls it in. > >In order to mitigate the performance penalty, decrease >PcdCpuSmmApSyncTimeout to one tenth of its default value: 100 ms. (For >comparison, Vlv2TbltDevicePkg sets 1 ms.) > >NOTE: once QEMU becomes capable of synchronous broadcast SMIs, this >patch >and the previous one ("OvmfPkg: use relaxed AP SMM synchronization >mode") >should be reverted, and SmmControl2DxeTrigger() should be adjusted >instead. > >Cc: Paolo Bonzini <pbonz...@redhat.com> >Cc: Jordan Justen <jordan.l.jus...@intel.com> >Cc: Michael Kinney <michael.d.kin...@intel.com> >Contributed-under: TianoCore Contribution Agreement 1.0 >Signed-off-by: Laszlo Ersek <ler...@redhat.com> >--- > >Notes: > v4: > - new in v4 > > OvmfPkg/OvmfPkgIa32.dsc | 1 + > OvmfPkg/OvmfPkgIa32X64.dsc | 1 + > OvmfPkg/OvmfPkgX64.dsc | 1 + > 3 files changed, 3 insertions(+) > >diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc >index 850c2ab..f9b7af7 100644 >--- a/OvmfPkg/OvmfPkgIa32.dsc >+++ b/OvmfPkg/OvmfPkgIa32.dsc >@@ -406,6 +406,7 @@ [PcdsFixedAtBuild] > > !if $(SMM_REQUIRE) == TRUE > gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01 >+ gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000 > !endif > > !if $(SECURE_BOOT_ENABLE) == TRUE >diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc >index 48960a5..028c21a 100644 >--- a/OvmfPkg/OvmfPkgIa32X64.dsc >+++ b/OvmfPkg/OvmfPkgIa32X64.dsc >@@ -412,6 +412,7 @@ [PcdsFixedAtBuild] > [PcdsFixedAtBuild.X64] > !if $(SMM_REQUIRE) == TRUE > gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01 >+ gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000 > !endif > > !if $(SECURE_BOOT_ENABLE) == TRUE >diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc >index bb93a72..5ee17ff 100644 >--- a/OvmfPkg/OvmfPkgX64.dsc >+++ b/OvmfPkg/OvmfPkgX64.dsc >@@ -411,6 +411,7 @@ [PcdsFixedAtBuild] > > !if $(SMM_REQUIRE) == TRUE > gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01 >+ gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000 > !endif > > !if $(SECURE_BOOT_ENABLE) == TRUE >-- >1.8.3.1 > _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
