The Linux persistent store (pstore) feature serves, among other things, for saving the trailing portion of the dmesg in case of a kernel oops. One backend for the pstore facility is "efivars", ie. non-volatile UEFI variables.
Linux splits the tail of the dmesg that is to be dumped in 1KB chunks, and tries to save each chunk as a specially (and differently) named non-volatile variable. The 1KB chunk size accounts for the variable data only; Linux expects this size to be available per variable *without* accounting for the variable name or any firmware-internal overhead. For non-authenticated (ie. non-secure-boot) variables, OvmfPkg currently sets the per-variable limit to 0x400 (1KB) through PcdMaxVariableSize. However this PCD determines the size *before* subtracting the internal overhead (which is sizeof(VARIABLE_HEADER) == 0x20 bytes for non-authenticated variables, see "MdeModulePkg/Include/Guid/VariableFormat.h"), and also before subtracting the given variable's UCS-2 encoded name (including the trailing 0x0000). Linux maximizes these special variable names in DUMP_NAME_LEN==52 code points (including the trailing NUL). Hence we must provide at least 0x020 == sizeof(VARIABLE_HEADER), for the internal overhead 0x068 == 2 * 52, for the UCS-2 encoded name, including trailing 0x0000 0x400 for the variable body ----- 0x488 == 1160 bytes in PcdMaxVariableSize, so that Linux's efivars-backed pstore can work even on non-secure-boot builds of OVMF. However, as PcdMaxVariableSize=0x2000 has proven reasonable when secure boot is enabled, it should also be okay when secure boot is disabled; so for simplicity's sake set PcdMaxVariableSize to 0x2000 unconditionally. Tested-by: Seiji Aguchi <[email protected]> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <[email protected]> --- OvmfPkg/OvmfPkgIa32.dsc | 4 ---- OvmfPkg/OvmfPkgIa32X64.dsc | 4 ---- OvmfPkg/OvmfPkgX64.dsc | 4 ---- 3 files changed, 12 deletions(-) diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc index c7c90fb..88d479d 100644 --- a/OvmfPkg/OvmfPkgIa32.dsc +++ b/OvmfPkg/OvmfPkgIa32.dsc @@ -276,11 +276,7 @@ gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10 gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxFvSupported|6 gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxPeimPerFv|32 -!if $(SECURE_BOOT_ENABLE) == TRUE gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000 -!else - gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x400 -!endif gEfiMdeModulePkgTokenSpaceGuid.PcdMaxHardwareErrorVariableSize|0x8000 gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0xe000 diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc index b8c569a..f19b658 100644 --- a/OvmfPkg/OvmfPkgIa32X64.dsc +++ b/OvmfPkg/OvmfPkgIa32X64.dsc @@ -281,11 +281,7 @@ gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10 gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxFvSupported|6 gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxPeimPerFv|32 -!if $(SECURE_BOOT_ENABLE) == TRUE gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000 -!else - gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x400 -!endif gEfiMdeModulePkgTokenSpaceGuid.PcdMaxHardwareErrorVariableSize|0x8000 gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0xe000 diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc index 70f3493..a927564 100644 --- a/OvmfPkg/OvmfPkgX64.dsc +++ b/OvmfPkg/OvmfPkgX64.dsc @@ -281,11 +281,7 @@ gEfiMdePkgTokenSpaceGuid.PcdMaximumGuidedExtractHandler|0x10 gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxFvSupported|6 gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxPeimPerFv|32 -!if $(SECURE_BOOT_ENABLE) == TRUE gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000 -!else - gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x400 -!endif gEfiMdeModulePkgTokenSpaceGuid.PcdMaxHardwareErrorVariableSize|0x8000 gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0xe000 -- 1.8.3.1 ------------------------------------------------------------------------------ CenturyLink Cloud: The Leader in Enterprise Cloud Services. Learn Why More Businesses Are Choosing CenturyLink Cloud For Critical Workloads, Development Environments & Everything In Between. Get a Quote or Start a Free Trial Today. http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk _______________________________________________ edk2-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/edk2-devel
