[PATCH v2] x86/resctrl: Don't stop walking closids when a locksetup group is found

[PATCH v2] x86/resctrl: Don't stop walking closids when a locksetup group is found

[James Morse]

When a new control group is created __init_one_rdt_domain() walks all
the other closids to calculate the sets of used and unused bits.

If it discovers a pseudo_locksetup group, it breaks out of the loop.
This means any later closid doesn't get its used bits added to used_b.
These bits will then get set in unused_b, and added to the new
control group's configuration, even if they were marked as exclusive
for a later closid.

When encountering a pseudo_locksetup group, we should continue. This
is because "a resource group enters 'pseudo-locked' mode after the
schemata is written while the resource group is in 'pseudo-locksetup'
mode." When we find a pseudo_locksetup group, its configuration is
expected to be overwritten, we can skip it.

Fixes: dfe9674b04ff6 ("x86/intel_rdt: Enable entering of pseudo-locksetup mode")
Cc: <stable@vger.kernel.org>
Acked-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v1:
 * Removed braces round multi-line comment and whitespace after the if() block

 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 333c177a2471..869cbef5da81 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2542,7 +2542,12 @@ static int __init_one_rdt_domain(struct rdt_domain *d, struct rdt_resource *r,
 		if (closid_allocated(i) && i != closid) {
 			mode = rdtgroup_mode_by_closid(i);
 			if (mode == RDT_MODE_PSEUDO_LOCKSETUP)
-				break;
+				/*
+				 * ctrl values for locksetup aren't relevant
+				 * until the schemata is written, and the mode
+				 * becomes RDT_MODE_PSEUDO_LOCKED.
+				 */
+				continue;
 			/*
 			 * If CDP is active include peer domain's
 			 * usage to ensure there is no overlap
-- 
2.20.1

Re: [PATCH v2] x86/resctrl: Don't stop walking closids when a locksetup group is found

[James Morse]

Hi,

On 06/06/2019 14:08, Sasha Levin wrote:
> This commit has been processed because it contains a "Fixes:" tag,
> fixing commit: dfe9674b04ff x86/intel_rdt: Enable entering of pseudo-locksetup mode.
> 
> The bot has tested the following trees: v5.1.7, v5.0.21, v4.19.48.

> v5.1.7: Failed to apply!  Possible dependencies:>     7390619ab9ea ("x86/resctrl: Move per RDT domain initialization to a separate function")
> 
> v5.0.21: Failed to apply! Possible dependencies:
>     7390619ab9ea ("x86/resctrl: Move per RDT domain initialization to a separate function")
That's cleanup, I don't think you want for stable. I'll do a backport.


> v4.19.48: Failed to apply! Possible dependencies:
>     2a7adf6ce643 ("x86/intel_rdt: Fix initial allocation to consider CDP")

This one changed an adjacent line.


>     723f1a0dd8e2 ("x86/resctrl: Fixup the user-visible strings")
>     7390619ab9ea ("x86/resctrl: Move per RDT domain initialization to a separate function")

> How should we proceed with this patch?

I'll come up with backports for v5.1.x/v5.0.x and v4.19.x once this reaches mainline.


Thanks,

James

[tip:x86/urgent] x86/resctrl: Don't stop walking closids when a locksetup group is found

[tip-bot for James Morse]

Commit-ID:  87d3aa28f345bea77c396855fa5d5fec4c24461f
Gitweb:     https://git.kernel.org/tip/87d3aa28f345bea77c396855fa5d5fec4c24461f
Author:     James Morse <james.morse@arm.com>
AuthorDate: Mon, 3 Jun 2019 18:25:31 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 12 Jun 2019 10:31:50 +0200

x86/resctrl: Don't stop walking closids when a locksetup group is found

When a new control group is created __init_one_rdt_domain() walks all
the other closids to calculate the sets of used and unused bits.

If it discovers a pseudo_locksetup group, it breaks out of the loop.  This
means any later closid doesn't get its used bits added to used_b.  These
bits will then get set in unused_b, and added to the new control group's
configuration, even if they were marked as exclusive for a later closid.

When encountering a pseudo_locksetup group, we should continue. This is
because "a resource group enters 'pseudo-locked' mode after the schemata is
written while the resource group is in 'pseudo-locksetup' mode." When we
find a pseudo_locksetup group, its configuration is expected to be
overwritten, we can skip it.

Fixes: dfe9674b04ff6 ("x86/intel_rdt: Enable entering of pseudo-locksetup mode")
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Reinette Chatre <reinette.chatre@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H Peter Avin <hpa@zytor.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20190603172531.178830-1-james.morse@arm.com

---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 333c177a2471..869cbef5da81 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2542,7 +2542,12 @@ static int __init_one_rdt_domain(struct rdt_domain *d, struct rdt_resource *r,
 		if (closid_allocated(i) && i != closid) {
 			mode = rdtgroup_mode_by_closid(i);
 			if (mode == RDT_MODE_PSEUDO_LOCKSETUP)
-				break;
+				/*
+				 * ctrl values for locksetup aren't relevant
+				 * until the schemata is written, and the mode
+				 * becomes RDT_MODE_PSEUDO_LOCKED.
+				 */
+				continue;
 			/*
 			 * If CDP is active include peer domain's
 			 * usage to ensure there is no overlap