2023-09-14 17:24:00

by James Morse

Subject: [PATCH v6 18/24] x86/resctrl: Make rdt_enable_key the arch's decision to switch

rdt_enable_key is switched when resctrl is mounted. It was also previously
used to prevent a second mount of the filesystem.

Any other architecture that wants to support resctrl has to provide
identical static keys.

Now that there are helpers for enabling and disabling the alloc/mon keys,
resctrl doesn't need to switch this extra key, it can be done by the arch
code. Use the static-key increment and decrement helpers, and change
resctrl to ensure the calls are balanced.

Reviewed-by: Shaopeng Tan <[email protected]>
Tested-by: Shaopeng Tan <[email protected]>
Tested-By: Peter Newman <[email protected]>
Signed-off-by: James Morse <[email protected]>
---
arch/x86/include/asm/resctrl.h | 4 ++++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 11 +++++------
2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index 3c9137b6ad4f..b74aa34dc9e8 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -45,21 +45,25 @@ DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
static inline void resctrl_arch_enable_alloc(void)
{
static_branch_enable_cpuslocked(&rdt_alloc_enable_key);
+ static_branch_inc_cpuslocked(&rdt_enable_key);
}

static inline void resctrl_arch_disable_alloc(void)
{
static_branch_disable_cpuslocked(&rdt_alloc_enable_key);
+ static_branch_dec_cpuslocked(&rdt_enable_key);
}

static inline void resctrl_arch_enable_mon(void)
{
static_branch_enable_cpuslocked(&rdt_mon_enable_key);
+ static_branch_inc_cpuslocked(&rdt_enable_key);
}

static inline void resctrl_arch_disable_mon(void)
{
static_branch_disable_cpuslocked(&rdt_mon_enable_key);
+ static_branch_dec_cpuslocked(&rdt_enable_key);
}

/*
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 4c0e012142e2..a2391cc05f20 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2546,10 +2546,8 @@ static int rdt_get_tree(struct fs_context *fc)
if (rdt_mon_capable)
resctrl_arch_enable_mon();

- if (rdt_alloc_capable || rdt_mon_capable) {
- static_branch_enable_cpuslocked(&rdt_enable_key);
+ if (rdt_alloc_capable || rdt_mon_capable)
resctrl_mounted = true;
- }

if (is_mbm_enabled()) {
r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
@@ -2817,9 +2815,10 @@ static void rdt_kill_sb(struct super_block *sb)
rdt_pseudo_lock_release();
rdtgroup_default.mode = RDT_MODE_SHAREABLE;
schemata_list_destroy();
- resctrl_arch_disable_alloc();
- resctrl_arch_disable_mon();
- static_branch_disable_cpuslocked(&rdt_enable_key);
+ if (rdt_alloc_capable)
+ resctrl_arch_disable_alloc();
+ if (rdt_mon_capable)
+ resctrl_arch_disable_mon();
resctrl_mounted = false;
kernfs_kill_sb(sb);
mutex_unlock(&rdtgroup_mutex);
--
2.39.2

2023-10-03 21:20:01

by Reinette Chatre

Subject: Re: [PATCH v6 18/24] x86/resctrl: Make rdt_enable_key the arch's decision to switch

Hi James,

On 9/14/2023 10:21 AM, James Morse wrote:
> rdt_enable_key is switched when resctrl is mounted. It was also previously
> used to prevent a second mount of the filesystem.
>
> Any other architecture that wants to support resctrl has to provide
> identical static keys.
>
> Now that there are helpers for enabling and disabling the alloc/mon keys,
> resctrl doesn't need to switch this extra key, it can be done by the arch
> code. Use the static-key increment and decrement helpers, and change
> resctrl to ensure the calls are balanced.
>
> Reviewed-by: Shaopeng Tan <[email protected]>
> Tested-by: Shaopeng Tan <[email protected]>
> Tested-By: Peter Newman <[email protected]>
> Signed-off-by: James Morse <[email protected]>
> ---

Reviewed-by: Reinette Chatre <[email protected]>

Reinette