On Mon, 11 Feb 2019 at 15:41, Leif Lindholm <[email protected]> wrote: > > On Wed, Feb 06, 2019 at 12:08:22AM +0000, Ard Biesheuvel wrote: > > Replace the dummy C implementation of SpeculationBarrier() with > > implementations consisting of the recommended DSB SY + ISB sequence, > > as recommended by ARM in the whitepaper "Cache Speculation Side-channels" > > version 2.4, dated October 2018. > > > > Contributed-under: TianoCore Contribution Agreement 1.1 > > Signed-off-by: Ard Biesheuvel <[email protected]> > > Patch looks fine. > Reviewed-by: Leif Lindholm <[email protected]> > > Question: do we expect performance impact to be sufficient to > motivate a Pcd to be able to disable the barrier on unaffected > processors? >
Currently, these are only used on some codepaths in the MM component of the variable store, which do not look like hot paths to me. In general, I think it should be fine to defer doing something like this until someone highlights it as an actual problem (and has the numbers to prove it) > > --- > > MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S | 39 > > ++++++++++++++++++++ > > MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm | 38 > > +++++++++++++++++++ > > MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S | 39 > > ++++++++++++++++++++ > > MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm | 39 > > ++++++++++++++++++++ > > MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c | 30 --------------- > > MdePkg/Library/BaseLib/BaseLib.inf | 7 +++- > > 6 files changed, 160 insertions(+), 32 deletions(-) > > > > diff --git a/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S > > b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S > > new file mode 100644 > > index 000000000000..500bdadca5d2 > > --- /dev/null > > +++ b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.S > > @@ -0,0 +1,39 @@ > > +##------------------------------------------------------------------------------ > > +# > > +# SpeculationBarrier() for AArch64 > > +# > > +# Copyright (c) 2019, Linaro Ltd. All rights reserved. > > +# > > +# This program and the accompanying materials > > +# are licensed and made available under the terms and conditions of the > > BSD License > > +# which accompanies this distribution. The full text of the license may > > be found at > > +# http://opensource.org/licenses/bsd-license.php. > > +# > > +# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, > > +# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR > > IMPLIED. > > +# > > +##------------------------------------------------------------------------------ > > + > > +.text > > +.p2align 2 > > + > > +GCC_ASM_EXPORT(SpeculationBarrier) > > + > > + > > +#/** > > +# Uses as a barrier to stop speculative execution. > > +# > > +# Ensures that no later instruction will execute speculatively, until all > > prior > > +# instructions have completed. > > +# > > +#**/ > > +#VOID > > +#EFIAPI > > +#SpeculationBarrier ( > > +# VOID > > +# ); > > +# > > +ASM_PFX(SpeculationBarrier): > > + dsb sy > > + isb > > + ret > > diff --git a/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm > > b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm > > new file mode 100644 > > index 000000000000..0c4b915b7798 > > --- /dev/null > > +++ b/MdePkg/Library/BaseLib/AArch64/SpeculationBarrier.asm > > @@ -0,0 +1,38 @@ > > +;------------------------------------------------------------------------------ > > +; > > +; SpeculationBarrier() for AArch64 > > +; > > +; Copyright (c) 2019, Linaro Ltd. All rights reserved. > > +; > > +; This program and the accompanying materials > > +; are licensed and made available under the terms and conditions of the > > BSD License > > +; which accompanies this distribution. The full text of the license may > > be found at > > +; http://opensource.org/licenses/bsd-license.php. > > +; > > +; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, > > +; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR > > IMPLIED. > > +; > > +;------------------------------------------------------------------------------ > > + > > + EXPORT SpeculationBarrier > > + AREA BaseLib_LowLevel, CODE, READONLY > > + > > +;/** > > +; Uses as a barrier to stop speculative execution. > > +; > > +; Ensures that no later instruction will execute speculatively, until all > > prior > > +; instructions have completed. > > +; > > +;**/ > > +;VOID > > +;EFIAPI > > +;SpeculationBarrier ( > > +; VOID > > +; ); > > +; > > +SpeculationBarrier > > + dsb sy > > + isb > > + ret > > + > > + END > > diff --git a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S > > b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S > > new file mode 100644 > > index 000000000000..7857558aba17 > > --- /dev/null > > +++ b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.S > > @@ -0,0 +1,39 @@ > > +##------------------------------------------------------------------------------ > > +# > > +# SpeculationBarrier() for AArch64 > > +# > > +# Copyright (c) 2019, Linaro Ltd. All rights reserved. > > +# > > +# This program and the accompanying materials > > +# are licensed and made available under the terms and conditions of the > > BSD License > > +# which accompanies this distribution. The full text of the license may > > be found at > > +# http://opensource.org/licenses/bsd-license.php. > > +# > > +# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, > > +# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR > > IMPLIED. > > +# > > +##------------------------------------------------------------------------------ > > + > > +.text > > +.p2align 2 > > + > > +GCC_ASM_EXPORT(SpeculationBarrier) > > + > > + > > +#/** > > +# Uses as a barrier to stop speculative execution. > > +# > > +# Ensures that no later instruction will execute speculatively, until all > > prior > > +# instructions have completed. > > +# > > +#**/ > > +#VOID > > +#EFIAPI > > +#SpeculationBarrier ( > > +# VOID > > +# ); > > +# > > +ASM_PFX(SpeculationBarrier): > > + dsb > > + isb > > + bx lr > > diff --git a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm > > b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm > > new file mode 100644 > > index 000000000000..425cd3de9e22 > > --- /dev/null > > +++ b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.asm > > @@ -0,0 +1,39 @@ > > +;------------------------------------------------------------------------------ > > +; > > +; SpeculationBarrier() for AArch64 > > +; > > +; Copyright (c) 2019, Linaro Ltd. All rights reserved. > > +; > > +; This program and the accompanying materials > > +; are licensed and made available under the terms and conditions of the > > BSD License > > +; which accompanies this distribution. The full text of the license may > > be found at > > +; http://opensource.org/licenses/bsd-license.php. > > +; > > +; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, > > +; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR > > IMPLIED. > > +; > > +;------------------------------------------------------------------------------ > > + > > + EXPORT SpeculationBarrier > > + > > + AREA MemoryBarriers, CODE, READONLY > > + > > +;/** > > +; Uses as a barrier to stop speculative execution. > > +; > > +; Ensures that no later instruction will execute speculatively, until all > > prior > > +; instructions have completed. > > +; > > +;**/ > > +;VOID > > +;EFIAPI > > +;SpeculationBarrier ( > > +; VOID > > +; ); > > +; > > +SpeculationBarrier > > + dsb > > + isb > > + bx lr > > + > > + END > > diff --git a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c > > b/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c > > deleted file mode 100644 > > index 8a6165a10227..000000000000 > > --- a/MdePkg/Library/BaseLib/Arm/SpeculationBarrier.c > > +++ /dev/null > > @@ -1,30 +0,0 @@ > > -/** @file > > - SpeculationBarrier() function for ARM. > > - > > - Copyright (C) 2018, Intel Corporation. All rights reserved.<BR> > > - > > - This program and the accompanying materials are licensed and made > > available > > - under the terms and conditions of the BSD License which accompanies this > > - distribution. The full text of the license may be found at > > - http://opensource.org/licenses/bsd-license.php. > > - > > - THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, > > WITHOUT > > - WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. > > - > > -**/ > > - > > - > > -/** > > - Uses as a barrier to stop speculative execution. > > - > > - Ensures that no later instruction will execute speculatively, until all > > prior > > - instructions have completed. > > - > > -**/ > > -VOID > > -EFIAPI > > -SpeculationBarrier ( > > - VOID > > - ) > > -{ > > -} > > diff --git a/MdePkg/Library/BaseLib/BaseLib.inf > > b/MdePkg/Library/BaseLib/BaseLib.inf > > index d195c5417b2e..f25a067a2335 100644 > > --- a/MdePkg/Library/BaseLib/BaseLib.inf > > +++ b/MdePkg/Library/BaseLib/BaseLib.inf > > @@ -552,7 +552,6 @@ > > [Sources.ARM] > > Arm/InternalSwitchStack.c > > Arm/Unaligned.c > > - Arm/SpeculationBarrier.c > > Math64.c | RVCT > > Math64.c | MSFT > > > > @@ -564,6 +563,7 @@ > > Arm/CpuPause.asm | RVCT > > Arm/CpuBreakpoint.asm | RVCT > > Arm/MemoryFence.asm | RVCT > > + Arm/SpeculationBarrier.S | RVCT > > > > Arm/SwitchStack.asm | MSFT > > Arm/SetJumpLongJump.asm | MSFT > > @@ -573,6 +573,7 @@ > > Arm/CpuPause.asm | MSFT > > Arm/CpuBreakpoint.asm | MSFT > > Arm/MemoryFence.asm | MSFT > > + Arm/SpeculationBarrier.asm | MSFT > > > > Arm/Math64.S | GCC > > Arm/SwitchStack.S | GCC > > @@ -582,11 +583,11 @@ > > Arm/SetJumpLongJump.S | GCC > > Arm/CpuBreakpoint.S | GCC > > Arm/MemoryFence.S | GCC > > + Arm/SpeculationBarrier.S | GCC > > > > [Sources.AARCH64] > > Arm/InternalSwitchStack.c > > Arm/Unaligned.c > > - Arm/SpeculationBarrier.c > > Math64.c > > > > AArch64/MemoryFence.S | GCC > > @@ -596,6 +597,7 @@ > > AArch64/GetInterruptsState.S | GCC > > AArch64/SetJumpLongJump.S | GCC > > AArch64/CpuBreakpoint.S | GCC > > + AArch64/SpeculationBarrier.S | GCC > > > > AArch64/MemoryFence.asm | MSFT > > AArch64/SwitchStack.asm | MSFT > > @@ -604,6 +606,7 @@ > > AArch64/GetInterruptsState.asm | MSFT > > AArch64/SetJumpLongJump.asm | MSFT > > AArch64/CpuBreakpoint.asm | MSFT > > + AArch64/SpeculationBarrier.asm | MSFT > > > > [Packages] > > MdePkg/MdePkg.dec > > -- > > 2.17.1 > > _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
