[PATCH 5.19 215/717] x86/resctrl: Fix to restore to original value when re-enabling hardware prefetch register

Greg Kroah-Hartman
2022-10-22T08:05:14Z

From: Kohei Tarumizu <tarumizu.kohei@fujitsu.com>

[ Upstream commit 499c8bb4693d1c8d8f3d6dd38e5bdde3ff5bd906 ]

The current pseudo_lock.c code overwrites the value of the
MSR_MISC_FEATURE_CONTROL to 0 even if the original value is not 0.
Therefore, modify it to save and restore the original values.

Fixes: 018961ae5579 ("x86/intel_rdt: Pseudo-lock region creation/removal core")
Fixes: 443810fe6160 ("x86/intel_rdt: Create debugfs files for pseudo-locking testing")
Fixes: 8a2fc0e1bc0c ("x86/intel_rdt: More precise L2 hit/miss measurements")
Signed-off-by: Kohei Tarumizu <tarumizu.kohei@fujitsu.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lkml.kernel.org/r/eb660f3c2010b79a792c573c02d01e8e841206ad.1661358182.git.reinette.chatre@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
index db813f819ad6..4d8398986f78 100644
--- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
+++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
@@ -420,6 +420,7 @@ static int pseudo_lock_fn(void *_rdtgrp)
struct pseudo_lock_region *plr = rdtgrp->plr;
u32 rmid_p, closid_p;
unsigned long i;
+ u64 saved_msr;
#ifdef CONFIG_KASAN
/*
* The registers used for local register variables are also used
@@ -463,6 +464,7 @@ static int pseudo_lock_fn(void *_rdtgrp)
* the buffer and evict pseudo-locked memory read earlier from the
* cache.
*/
+ saved_msr = __rdmsr(MSR_MISC_FEATURE_CONTROL);
__wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
closid_p = this_cpu_read(pqr_state.cur_closid);
rmid_p = this_cpu_read(pqr_state.cur_rmid);
@@ -514,7 +516,7 @@ static int pseudo_lock_fn(void *_rdtgrp)
__wrmsr(IA32_PQR_ASSOC, rmid_p, closid_p);

/* Re-enable the hardware prefetcher(s) */
- wrmsr(MSR_MISC_FEATURE_CONTROL, 0x0, 0x0);
+ wrmsrl(MSR_MISC_FEATURE_CONTROL, saved_msr);
local_irq_enable();

plr->thread_done = 1;
@@ -871,6 +873,7 @@ bool rdtgroup_pseudo_locked_in_hierarchy(struct rdt_domain *d)
static int measure_cycles_lat_fn(void *_plr)
{
struct pseudo_lock_region *plr = _plr;
+ u32 saved_low, saved_high;
unsigned long i;
u64 start, end;
void *mem_r;
@@ -879,6 +882,7 @@ static int measure_cycles_lat_fn(void *_plr)
/*
* Disable hardware prefetchers.
*/
+ rdmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
mem_r = READ_ONCE(plr->kmem);
/*
@@ -895,7 +899,7 @@ static int measure_cycles_lat_fn(void *_plr)
end = rdtsc_ordered();
trace_pseudo_lock_mem_latency((u32)(end - start));
}
- wrmsr(MSR_MISC_FEATURE_CONTROL, 0x0, 0x0);
+ wrmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
local_irq_enable();
plr->thread_done = 1;
wake_up_interruptible(&plr->lock_thread_wq);
@@ -940,6 +944,7 @@ static int measure_residency_fn(struct perf_event_attr *miss_attr,
u64 hits_before = 0, hits_after = 0, miss_before = 0, miss_after = 0;
struct perf_event *miss_event, *hit_event;
int hit_pmcnum, miss_pmcnum;
+ u32 saved_low, saved_high;
unsigned int line_size;
unsigned int size;
unsigned long i;
@@ -973,6 +978,7 @@ static int measure_residency_fn(struct perf_event_attr *miss_attr,
/*
* Disable hardware prefetchers.
*/
+ rdmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);

/* Initialize rest of local variables */
@@ -1031,7 +1037,7 @@ static int measure_residency_fn(struct perf_event_attr *miss_attr,
*/
rmb();
/* Re-enable hardware prefetchers */
- wrmsr(MSR_MISC_FEATURE_CONTROL, 0x0, 0x0);
+ wrmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
local_irq_enable();
out_hit:
perf_event_release_kernel(hit_event);
--
2.35.1