arm-trusted-firmware/lib/cpus/aarch64/cortex_a720.S
Boyan Karatotev 89dba82dfa perf(cpus): make reset errata do fewer branches
Errata application is painful for performance. For a start, it's done
when the core has just come out of reset, which means branch predictors
and caches will be empty so a branch to a workaround function must be
fetched from memory and that round trip is very slow. Then it also runs
with the I-cache off, which means that the loop to iterate over the
workarounds must also be fetched from memory on each iteration.

We can remove both branches. First, we can simply apply every erratum
directly instead of defining a workaround function and jumping to it.
Currently, no errata that need to be applied at both reset and runtime,
with the same workaround function, exist. If the need arose in future,
this should be achievable with a reset + runtime wrapper combo.

Then, we can construct a function that applies each erratum linearly
instead of looping over the list. If this function is part of the reset
function, then the only "far" branches at reset will be for the checker
functions. Importantly, this mitigates the slowdown even when an erratum
is disabled.

The result is ~50% speedup on N1SDP and ~20% on AArch64 Juno on wakeup
from PSCI calls that end in powerdown. This is roughly back to the
baseline of v2.9, before the errata framework regressed on performance
(or a little better). It is important to note that there are other
slowdowns since then that remain unknown.

Change-Id: Ie4d5288a331b11fd648e5c4a0b652b74160b07b9
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
2025-02-24 09:36:11 +00:00

124 lines
4 KiB
ArmAsm

/*
* Copyright (c) 2021-2025, Arm Limited. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <arch.h>
#include <asm_macros.S>
#include <common/bl_common.h>
#include <cortex_a720.h>
#include <cpu_macros.S>
#include <plat_macros.S>
#include "wa_cve_2022_23960_bhb_vector.S"
/* Hardware handled coherency */
#if HW_ASSISTED_COHERENCY == 0
#error "Cortex A720 must be compiled with HW_ASSISTED_COHERENCY enabled"
#endif
/* 64-bit only core */
#if CTX_INCLUDE_AARCH32_REGS == 1
#error "Cortex A720 supports only AArch64. Compile with CTX_INCLUDE_AARCH32_REGS=0"
#endif
cpu_reset_prologue cortex_a720
.global check_erratum_cortex_a720_3699561
#if WORKAROUND_CVE_2022_23960
wa_cve_2022_23960_bhb_vector_table CORTEX_A720_BHB_LOOP_COUNT, cortex_a720
#endif /* WORKAROUND_CVE_2022_23960 */
workaround_reset_start cortex_a720, ERRATUM(2792132), ERRATA_A720_2792132
sysreg_bit_set CORTEX_A720_CPUACTLR2_EL1, BIT(26)
workaround_reset_end cortex_a720, ERRATUM(2792132)
check_erratum_ls cortex_a720, ERRATUM(2792132), CPU_REV(0, 1)
workaround_reset_start cortex_a720, ERRATUM(2844092), ERRATA_A720_2844092
sysreg_bit_set CORTEX_A720_CPUACTLR4_EL1, BIT(11)
workaround_reset_end cortex_a720, ERRATUM(2844092)
check_erratum_ls cortex_a720, ERRATUM(2844092), CPU_REV(0, 1)
workaround_reset_start cortex_a720, ERRATUM(2926083), ERRATA_A720_2926083
/* Erratum 2926083 workaround is required only if SPE is enabled */
#if ENABLE_SPE_FOR_NS != 0
/* Check if Static profiling extension is implemented or present. */
mrs x1, id_aa64dfr0_el1
ubfx x0, x1, ID_AA64DFR0_PMS_SHIFT, #4
cbz x0, 1f
/* Apply the workaround by setting CPUACTLR_EL1[58:57] = 0b11. */
sysreg_bit_set CORTEX_A720_CPUACTLR_EL1, BIT(57)
sysreg_bit_set CORTEX_A720_CPUACTLR_EL1, BIT(58)
1:
#endif
workaround_reset_end cortex_a720, ERRATUM(2926083)
check_erratum_ls cortex_a720, ERRATUM(2926083), CPU_REV(0, 1)
workaround_reset_start cortex_a720, ERRATUM(2940794), ERRATA_A720_2940794
sysreg_bit_set CORTEX_A720_CPUACTLR2_EL1, BIT(37)
workaround_reset_end cortex_a720, ERRATUM(2940794)
check_erratum_ls cortex_a720, ERRATUM(2940794), CPU_REV(0, 1)
workaround_reset_start cortex_a720, CVE(2022, 23960), WORKAROUND_CVE_2022_23960
#if IMAGE_BL31
/*
* The Cortex A720 generic vectors are overridden to apply errata
* mitigation on exception entry from lower ELs.
*/
override_vector_table wa_cve_vbar_cortex_a720
#endif /* IMAGE_BL31 */
workaround_reset_end cortex_a720, CVE(2022, 23960)
check_erratum_chosen cortex_a720, CVE(2022, 23960), WORKAROUND_CVE_2022_23960
add_erratum_entry cortex_a720, ERRATUM(3699561), ERRATA_A720_3699561
check_erratum_ls cortex_a720, ERRATUM(3699561), CPU_REV(0, 2)
cpu_reset_func_start cortex_a720
/* Disable speculative loads */
msr SSBS, xzr
cpu_reset_func_end cortex_a720
/* ----------------------------------------------------
* HW will do the cache maintenance while powering down
* ----------------------------------------------------
*/
func cortex_a720_core_pwr_dwn
/* ---------------------------------------------------
* Enable CPU power down bit in power control register
* ---------------------------------------------------
*/
sysreg_bit_set CORTEX_A720_CPUPWRCTLR_EL1, CORTEX_A720_CPUPWRCTLR_EL1_CORE_PWRDN_BIT
isb
ret
endfunc cortex_a720_core_pwr_dwn
/* ---------------------------------------------
* This function provides Cortex A720-specific
* register information for crash reporting.
* It needs to return with x6 pointing to
* a list of register names in ascii and
* x8 - x15 having values of registers to be
* reported.
* ---------------------------------------------
*/
.section .rodata.cortex_a720_regs, "aS"
cortex_a720_regs: /* The ascii list of register names to be reported */
.asciz "cpuectlr_el1", ""
func cortex_a720_cpu_reg_dump
adr x6, cortex_a720_regs
mrs x8, CORTEX_A720_CPUECTLR_EL1
ret
endfunc cortex_a720_cpu_reg_dump
declare_cpu_ops cortex_a720, CORTEX_A720_MIDR, \
cortex_a720_reset_func, \
cortex_a720_core_pwr_dwn