On Thu, 10 Dec 2020, Luca Fancellu wrote:
> On the Cortex A53, when executing in AArch64 state, a load or store
> instruction
> which uses the result of an ADRP instruction as a base register, or which uses
> a base register written by an instruction immediately after an ADRP to the
> same register, might access an incorrect address.
>
> The workaround is to enable the linker flag --fix-cortex-a53-843419
> if present, to check and fix the affected sequence. Otherwise print a warning
> that Xen may be susceptible to this errata
>
> Signed-off-by: Luca Fancellu <luca.fance...@arm.com>
> ---
> docs/misc/arm/silicon-errata.txt | 1 +
> xen/arch/arm/Kconfig | 19 +++++++++++++++++++
> xen/arch/arm/Makefile | 8 ++++++++
> xen/scripts/Kbuild.include | 12 ++++++++++++
> 4 files changed, 40 insertions(+)
>
> diff --git a/docs/misc/arm/silicon-errata.txt
> b/docs/misc/arm/silicon-errata.txt
> index 27bf957ebf..1925d8fd4e 100644
> --- a/docs/misc/arm/silicon-errata.txt
> +++ b/docs/misc/arm/silicon-errata.txt
> @@ -45,6 +45,7 @@ stable hypervisors.
> | ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319
> |
> | ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069
> |
> | ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472
> |
> +| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419
> |
> | ARM | Cortex-A55 | #1530923 | N/A
> |
> | ARM | Cortex-A57 | #852523 | N/A
> |
> | ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075
> |
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index f5b1bcda03..41bde2f401 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -186,6 +186,25 @@ config ARM64_ERRATUM_819472
>
> If unsure, say Y.
>
> +config ARM64_ERRATUM_843419
> + bool "Cortex-A53: 843419: A load or store might access an incorrect
> address"
> + default y
> + depends on ARM_64
> + help
> + This option adds an alternative code sequence to work around ARM
> + erratum 843419 on Cortex-A53 parts up to r0p4.
> +
> + When executing in AArch64 state, a load or store instruction which
> uses
> + the result of an ADRP instruction as a base register, or which uses a
> + base register written by an instruction immediately after an ADRP to
> the
> + same register, might access an incorrect address.
> +
> + The workaround enables the linker to check if the affected sequence is
> + produced and it will fix it with an alternative not affected sequence
> + that produce the same behavior.
> +
> + If unsure, say Y.
> +
> config ARM64_ERRATUM_832075
> bool "Cortex-A57: 832075: possible deadlock on mixing exclusive memory
> accesses with device loads"
> default y
> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> index 296c5e68bb..ad2d497c45 100644
> --- a/xen/arch/arm/Makefile
> +++ b/xen/arch/arm/Makefile
> @@ -101,6 +101,14 @@ prelink.o: $(ALL_OBJS) FORCE
> $(call if_changed,ld)
> endif
>
> +ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
> + ifeq ($(call ld-option, --fix-cortex-a53-843419),n)
> + $(warning ld does not support --fix-cortex-a53-843419; xen may be
> susceptible to erratum)
> + else
> + XEN_LDFLAGS += --fix-cortex-a53-843419
> + endif
> +endif
I was going to comment that maybe we should put the warning elsewhere.
However, I tested the patch and works fine with both new and old
compilers and you really need to go way back to gcc 4.9 to trigger the
warning, so on second thought I think it is OK as is.
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
> targets += prelink.o
>
> $(TARGET)-syms: prelink.o xen.lds
> diff --git a/xen/scripts/Kbuild.include b/xen/scripts/Kbuild.include
> index e62eddc365..83c7e1457b 100644
> --- a/xen/scripts/Kbuild.include
> +++ b/xen/scripts/Kbuild.include
> @@ -43,6 +43,18 @@ define as-option-add-closure
> endif
> endef
>
> +# $(if-success,<command>,<then>,<else>)
> +# Return <then> if <command> exits with 0, <else> otherwise.
> +if-success = $(shell { $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)")
> +
> +# $(success,<command>)
> +# Return y if <command> exits with 0, n otherwise
> +success = $(call if-success,$(1),y,n)
> +
> +# $(ld-option,<flag>)
> +# Return y if the linker supports <flag>, n otherwise
> +ld-option = $(call success,$(LD) -v $(1))
> +
> # cc-ifversion
> # Usage: EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
> cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3)
> || echo $(4))
> --
> 2.17.1
>
