Messages in this thread | | | Date | Thu, 8 Dec 2016 11:31:43 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH 2/3] arm64: Work around Falkor erratum 1003 |
| |
On Wed, Dec 07, 2016 at 03:00:26PM -0500, Christopher Covington wrote: > From: Shanker Donthineni <shankerd@codeaurora.org> > > On the Qualcomm Datacenter Technologies Falkor v1 CPU, memory accesses may > allocate TLB entries using an incorrect ASID when TTBRx_EL1 is being > updated. Changing the TTBRx_EL1[ASID] and TTBRx_EL1[BADDR] fields > separately using a reserved ASID will ensure that there are no TLB entries > with incorrect ASID after changing the the ASID. > > Pseudo code: > write TTBRx_EL1[ASID] to a reserved value > ISB > write TTBRx_EL1[BADDR] to a desired value > ISB > write TTBRx_EL1[ASID] to a desired value > ISB > > Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org> > Signed-off-by: Christopher Covington <cov@codeaurora.org> > --- > arch/arm64/Kconfig | 11 +++++++++++ > arch/arm64/include/asm/cpucaps.h | 3 ++- > arch/arm64/kernel/cpu_errata.c | 7 +++++++ > arch/arm64/mm/context.c | 10 ++++++++++ > arch/arm64/mm/proc.S | 21 +++++++++++++++++++++ > 5 files changed, 51 insertions(+), 1 deletion(-)
This needs an update to Documentation/arm64/silicon-errata.txt.
> diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c > index efcf1f7..f8d94ff 100644 > --- a/arch/arm64/mm/context.c > +++ b/arch/arm64/mm/context.c > @@ -87,6 +87,11 @@ static void flush_context(unsigned int cpu) > /* Update the list of reserved ASIDs and the ASID bitmap. */ > bitmap_clear(asid_map, 0, NUM_USER_ASIDS); > > + /* Reserve ASID '1' for Falkor erratum E1003 */ > + if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_E1003) && > + cpus_have_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003)) > + __set_bit(1, asid_map); > + > /* > * Ensure the generation bump is observed before we xchg the > * active_asids. > @@ -239,6 +244,11 @@ static int asids_init(void) > panic("Failed to allocate bitmap for %lu ASIDs\n", > NUM_USER_ASIDS); > > + /* Reserve ASID '1' for Falkor erratum E1003 */ > + if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_E1003) && > + cpus_have_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003)) > + __set_bit(1, asid_map); > + > pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS); > return 0; > } > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > index 352c73b..b4d6508 100644 > --- a/arch/arm64/mm/proc.S > +++ b/arch/arm64/mm/proc.S > @@ -134,6 +134,27 @@ ENDPROC(cpu_do_resume) > ENTRY(cpu_do_switch_mm) > mmid x1, x1 // get mm->context.id > bfi x0, x1, #48, #16 // set the ASID > +#ifdef CONFIG_QCOM_FALKOR_ERRATUM_E1003 > +alternative_if_not ARM64_WORKAROUND_QCOM_FALKOR_E1003 > + nop > + nop > + nop > + nop > + nop > + nop > + nop > + nop > +alternative_else > + mrs x2, ttbr0_el1 // get cuurent TTBR0_EL1 > + mov x3, #1 // reserved ASID
It might be best to define a FALCOR_E1003_RESERVED_ASID constant somewhere, rather than using 1 directly here and in the ASID allocator.
> + bfi x2, x3, #48, #16 // set the reserved ASID + old BADDR > + msr ttbr0_el1, x2 // update TTBR0_EL1 > + isb > + bfi x2, x0, #0, #48 // set the desired BADDR + reserved ASID > + msr ttbr0_el1, x2 // update TTBR0_EL1 > + isb > +alternative_endif
Please use alternative_if and alternative_else_nop_endif.
As Catalin noted, there are issues with stale and/or conflicting TLB entries allocated with the reserved ASID, so we likely have to invalidate that after the final switch.
Thanks, Mark.
| |