[PATCH v7 25/49] x86/resctrl: Make prefetch_disable_bits belong to the arch code

James Morse
2025-02-28T20:01:30Z

prefetch_disable_bits is set by rdtgroup_locksetup_enter() from a
value provided by the architecture, but is largely read by other
architecture helpers.

Make resctrl_arch_get_prefetch_disable_bits() set prefetch_disable_bits
so that it can be isolated to arch-code from where the other arch-code
helpers can use its cached-value.

Signed-off-by: James Morse <james.morse@arm.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
Changes since v5:
* Tweaked the word 'export'.
* Swapped the second paragraph for Reinette's version.
---
arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
index 1f42c1190d26..90044a01d000 100644
--- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
+++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
@@ -84,6 +84,8 @@ static const struct class pseudo_lock_class = {
*/
u64 resctrl_arch_get_prefetch_disable_bits(void)
{
+ prefetch_disable_bits = 0;
+
if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
boot_cpu_data.x86 != 6)
return 0;
@@ -99,7 +101,8 @@ u64 resctrl_arch_get_prefetch_disable_bits(void)
* 3 DCU IP Prefetcher Disable (R/W)
* 63:4 Reserved
*/
- return 0xF;
+ prefetch_disable_bits = 0xF;
+ break;
case INTEL_ATOM_GOLDMONT:
case INTEL_ATOM_GOLDMONT_PLUS:
/*
@@ -110,10 +113,11 @@ u64 resctrl_arch_get_prefetch_disable_bits(void)
* 2 DCU Hardware Prefetcher Disable (R/W)
* 63:3 Reserved
*/
- return 0x5;
+ prefetch_disable_bits = 0x5;
+ break;
}

- return 0;
+ return prefetch_disable_bits;
}

/**
@@ -713,8 +717,7 @@ int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp)
* Not knowing the bits to disable prefetching implies that this
* platform does not support Cache Pseudo-Locking.
*/
- prefetch_disable_bits = resctrl_arch_get_prefetch_disable_bits();
- if (prefetch_disable_bits == 0) {
+ if (resctrl_arch_get_prefetch_disable_bits() == 0) {
rdt_last_cmd_puts("Pseudo-locking not supported\n");
return -EINVAL;
}
--
2.39.5