On Thu, Jan 05, 2023 at 12:46:19PM +0100, Ard Biesheuvel wrote: > On Wed, 4 Jan 2023 at 18:23, Ard Biesheuvel <a...@kernel.org> wrote: > > > > The early ID map used by ArmVirtQemu uses ASID scoped non-global > > mappings, as this allows us to switch to the permanent ID map seamlessly > > without the need for explicit TLB maintenance. > > > > However, this triggers a known erratum on ThunderX, which does not > > tolerate non-global mappings that are executable at EL1, as this appears > > to result in I-cache corruption. (Linux disables the KPTI based Meltdown > > mitigation on ThunderX for the same reason) > > > > So work around this, by detecting the CPU implementor and part number, > > and proceeding without the early ID map if a ThunderX CPU is detected. > > > > Note that this requires the C code to be built with strict alignment > > again, as we may end up executing it with the MMU and caches off. > > > > Signed-off-by: Ard Biesheuvel <a...@kernel.org> > > --- > > ArmVirtPkg/ArmVirtQemu.dsc | 6 > > ++++++ > > ArmVirtPkg/Library/ArmPlatformLibQemu/AArch64/ArmPlatformHelper.S | 18 > > ++++++++++++++++++ > > 2 files changed, 24 insertions(+) > > > > diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc > > index f77443229e8e..340b36f69c2c 100644 > > --- a/ArmVirtPkg/ArmVirtQemu.dsc > > +++ b/ArmVirtPkg/ArmVirtQemu.dsc > > @@ -31,6 +31,7 @@ [Defines] > > DEFINE SECURE_BOOT_ENABLE = FALSE > > DEFINE TPM2_ENABLE = FALSE > > DEFINE TPM2_CONFIG_ENABLE = FALSE > > + DEFINE CAVIUM_ERRATUM_27456 = FALSE > > > > # > > # Network definition > > @@ -117,7 +118,12 @@ [LibraryClasses.common.UEFI_DRIVER] > > UefiScsiLib|MdePkg/Library/UefiScsiLib/UefiScsiLib.inf > > > > [BuildOptions] > > +!if $(CAVIUM_ERRATUM_27456) == TRUE > > + GCC:*_*_AARCH64_CC_XIPFLAGS = -mno-strict-align > > This is wrong - this should be '-mstrict-align'
Ah, I wondered :) With that adjustment, the patch works for me on a Cavium ThunderX. Thanks Ard! -dann > > + GCC:*_*_AARCH64_PP_FLAGS = -DCAVIUM_ERRATUM_27456 > > +!else > > GCC:*_*_AARCH64_CC_XIPFLAGS == > > +!endif > > > > !include NetworkPkg/NetworkBuildOptions.dsc.inc > > > > diff --git > > a/ArmVirtPkg/Library/ArmPlatformLibQemu/AArch64/ArmPlatformHelper.S > > b/ArmVirtPkg/Library/ArmPlatformLibQemu/AArch64/ArmPlatformHelper.S > > index 05ccc7f9f043..962f1ba3a4d7 100644 > > --- a/ArmVirtPkg/Library/ArmPlatformLibQemu/AArch64/ArmPlatformHelper.S > > +++ b/ArmVirtPkg/Library/ArmPlatformLibQemu/AArch64/ArmPlatformHelper.S > > @@ -44,8 +44,26 @@ > > > > > > ASM_FUNC(ArmPlatformPeiBootAction) > > +#ifdef CAVIUM_ERRATUM_27456 > > + /* > > + * On Cavium ThunderX, using non-global mappings that are executable at > > EL1 > > + * results in I-cache corruption. So just avoid the early ID mapping > > there. > > + * > > + * MIDR implementor 0x43 > > + * MIDR part numbers 0xA1 0xA2 > > + */ > > + mrs x0, midr_el1 // read the MIDR into X0 > > + ubfx x1, x0, #6, #10 // grab part number bits [11:2] > > + ubfx x0, x0, #24, #8 // grab implementor id > > + mov x2, #0xA0 >> 2 > > + cmp x0, #0x43 // compare implementor id > > + ccmp x1, x2, #0, eq // compare part# bits [11:2] > > + b.eq .Lreturn > > +#endif > > + > > mrs x0, CurrentEL // check current exception level > > tbz x0, #3, 0f // bail if above EL1 > > +.Lreturn: > > ret > > > > 0:mov_i x0, mairval > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#98033): https://edk2.groups.io/g/devel/message/98033 Mute This Topic: https://groups.io/mt/96054879/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
