leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

arm64: Work around Falkor erratum 1003

Browse Source 
The Qualcomm Datacenter Technologies Falkor v1 CPU may allocate TLB entries
using an incorrect ASID when TTBRx_EL1 is being updated. When the erratum
is triggered, page table entries using the new translation table base
address (BADDR) will be allocated into the TLB using the old ASID. All
circumstances leading to the incorrect ASID being cached in the TLB arise
when software writes TTBRx_EL1[ASID] and TTBRx_EL1[BADDR], a memory
operation is in the process of performing a translation using the specific
TTBRx_EL1 being written, and the memory operation uses a translation table
descriptor designated as non-global. EL2 and EL3 code changing the EL1&0
ASID is not subject to this erratum because hardware is prohibited from
performing translations from an out-of-context translation regime.

Consider the following pseudo code.

  write new BADDR and ASID values to TTBRx_EL1

Replacing the above sequence with the one below will ensure that no TLB
entries with an incorrect ASID are used by software.

  write reserved value to TTBRx_EL1[ASID]
  ISB
  write new value to TTBRx_EL1[BADDR]
  ISB
  write new value to TTBRx_EL1[ASID]
  ISB

When the above sequence is used, page table entries using the new BADDR
value may still be incorrectly allocated into the TLB using the reserved
ASID. Yet this will not reduce functionality, since TLB entries incorrectly
tagged with the reserved ASID will never be hit by a later instruction.

Based on work by Shanker Donthineni <shankerd@codeaurora.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Christopher Covington 2017-02-08 15:08:37 -05:00 committed by Will Deacon
parent 2bf47e1946
commit 38fd94b027
8 changed files with 72 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Documentation/arm64/silicon-errata.txt
View File

@ -66,4 +66,5 @@ stable kernels.
| | | | |
| Hisilicon | Hip0{5,6,7} | #161010101 | HISILICON_ERRATUM_161010101 |
| | | | |
| Qualcomm Tech. | Falkor v1 | E1003 | QCOM_FALKOR_ERRATUM_1003 |
| Qualcomm Tech. | Falkor v1 | E1009 | QCOM_FALKOR_ERRATUM_1009 |

18
arch/arm64/Kconfig
View File

@ -480,6 +480,24 @@ config CAVIUM_ERRATUM_27456
If unsure, say Y.
config QCOM_FALKOR_ERRATUM_1003
bool "Falkor E1003: Incorrect translation due to ASID change"
default y
select ARM64_PAN if ARM64_SW_TTBR0_PAN
help
On Falkor v1, an incorrect ASID may be cached in the TLB when ASID
and BADDR are changed together in TTBRx_EL1. The workaround for this
issue is to use a reserved ASID in cpu_do_switch_mm() before
switching to the new ASID. Saying Y here selects ARM64_PAN if
ARM64_SW_TTBR0_PAN is selected. This is done because implementing and
maintaining the E1003 workaround in the software PAN emulation code
would be an unnecessary complication. The affected Falkor v1 CPU
implements ARMv8.1 hardware PAN support and using hardware PAN
support versus software PAN emulation is mutually exclusive at
runtime.
If unsure, say Y.
config QCOM_FALKOR_ERRATUM_1009
bool "Falkor E1009: Prematurely complete a DSB after a TLBI"
default y

23
arch/arm64/include/asm/assembler.h
View File

@ -25,6 +25,7 @@
#include <asm/asm-offsets.h>
#include <asm/cpufeature.h>
#include <asm/mmu_context.h>
#include <asm/page.h>
#include <asm/pgtable-hwdef.h>
#include <asm/ptrace.h>
@ -422,6 +423,28 @@ alternative_endif
mrs \rd, sp_el0
.endm
/*
* Errata workaround prior to TTBR0_EL1 update
*
* val: TTBR value with new BADDR, preserved
* tmp0: temporary register, clobbered
* tmp1: other temporary register, clobbered
*/
.macro pre_ttbr0_update_workaround, val, tmp0, tmp1
#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1003
mrs \tmp0, ttbr0_el1
mov \tmp1, #FALKOR_RESERVED_ASID
bfi \tmp0, \tmp1, #48, #16 // reserved ASID + old BADDR
msr ttbr0_el1, \tmp0
isb
bfi \tmp0, \val, #0, #48 // reserved ASID + new BADDR
msr ttbr0_el1, \tmp0
isb
alternative_else_nop_endif
#endif
.endm
/*
* Errata workaround post TTBR0_EL1 update.
*/

3
arch/arm64/include/asm/cpucaps.h
View File

@ -36,7 +36,8 @@
#define ARM64_MISMATCHED_CACHE_LINE_SIZE 15
#define ARM64_HAS_NO_FPSIMD 16
#define ARM64_WORKAROUND_REPEAT_TLBI 17
#define ARM64_WORKAROUND_QCOM_FALKOR_E1003 18
#define ARM64_NCAPS 18
#define ARM64_NCAPS 19
#endif /* __ASM_CPUCAPS_H */

8
arch/arm64/include/asm/mmu_context.h
View File

@ -19,6 +19,10 @@
#ifndef __ASM_MMU_CONTEXT_H
#define __ASM_MMU_CONTEXT_H
#define FALKOR_RESERVED_ASID 1
#ifndef __ASSEMBLY__
#include <linux/compiler.h>
#include <linux/sched.h>
@ -220,4 +224,6 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
void verify_cpu_asid_bits(void);
#endif
#endif /* !__ASSEMBLY__ */
#endif /* !__ASM_MMU_CONTEXT_H */

9
arch/arm64/kernel/cpu_errata.c
View File

@ -133,6 +133,15 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
.def_scope = SCOPE_LOCAL_CPU,
.enable = cpu_enable_trap_ctr_access,
},
#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
{
.desc = "Qualcomm Technologies Falkor erratum 1003",
.capability = ARM64_WORKAROUND_QCOM_FALKOR_E1003,
MIDR_RANGE(MIDR_QCOM_FALKOR_V1,
MIDR_CPU_VAR_REV(0, 0),
MIDR_CPU_VAR_REV(0, 0)),
},
#endif
#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1009
{
.desc = "Qualcomm Technologies Falkor erratum 1009",

11
arch/arm64/mm/context.c
View File

@ -79,6 +79,13 @@ void verify_cpu_asid_bits(void)
}
}
static void set_reserved_asid_bits(void)
{
if (IS_ENABLED(CONFIG_QCOM_FALKOR_ERRATUM_1003) &&
cpus_have_const_cap(ARM64_WORKAROUND_QCOM_FALKOR_E1003))
__set_bit(FALKOR_RESERVED_ASID, asid_map);
}
static void flush_context(unsigned int cpu)
{
int i;
@ -87,6 +94,8 @@ 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);
set_reserved_asid_bits();
/*
* Ensure the generation bump is observed before we xchg the
* active_asids.
@ -244,6 +253,8 @@ static int asids_init(void)
panic("Failed to allocate bitmap for %lu ASIDs\n",
NUM_USER_ASIDS);
set_reserved_asid_bits();
pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS);
return 0;
}

1
arch/arm64/mm/proc.S
View File

@ -138,6 +138,7 @@ ENDPROC(cpu_do_resume)
* - pgd_phys - physical address of new TTB
*/
ENTRY(cpu_do_switch_mm)
pre_ttbr0_update_workaround x0, x1, x2
mmid x1, x1 // get mm->context.id
bfi x0, x1, #48, #16 // set the ASID
msr ttbr0_el1, x0 // set TTBR0