[PATCH AUTOSEL 6.13 1/7] sched: Don't try to catch up excess steal time.

[PATCH AUTOSEL 6.13 1/7] sched: Don't try to catch up excess steal time.

[Sasha Levin]

From: Suleiman Souhlal <suleiman@google.com>

[ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ]

When steal time exceeds the measured delta when updating clock_task, we
currently try to catch up the excess in future updates.
However, this results in inaccurate run times for the future things using
clock_task, in some situations, as they end up getting additional steal
time that did not actually happen.
This is because there is a window between reading the elapsed time in
update_rq_clock() and sampling the steal time in update_rq_clock_task().
If the VCPU gets preempted between those two points, any additional
steal time is accounted to the outgoing task even though the calculated
delta did not actually contain any of that "stolen" time.
When this race happens, we can end up with steal time that exceeds the
calculated delta, and the previous code would try to catch up that excess
steal time in future clock updates, which is given to the next,
incoming task, even though it did not actually have any time stolen.

This behavior is particularly bad when steal time can be very long,
which we've seen when trying to extend steal time to contain the duration
that the host was suspended [0]. When this happens, clock_task stays
frozen, during which the running task stays running for the whole
duration, since its run time doesn't increase.
However the race can happen even under normal operation.

Ideally we would read the elapsed cpu time and the steal time atomically,
to prevent this race from happening in the first place, but doing so
is non-trivial.

Since the time between those two points isn't otherwise accounted anywhere,
neither to the outgoing task nor the incoming task (because the "end of
outgoing task" and "start of incoming task" timestamps are the same),
I would argue that the right thing to do is to simply drop any excess steal
time, in order to prevent these issues.

[0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/sched/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3e5a6bf587f91..296e77380318e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -766,13 +766,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
 #endif
 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
 	if (static_key_false((&paravirt_steal_rq_enabled))) {
-		steal = paravirt_steal_clock(cpu_of(rq));
+		u64 prev_steal;
+
+		steal = prev_steal = paravirt_steal_clock(cpu_of(rq));
 		steal -= rq->prev_steal_time_rq;
 
 		if (unlikely(steal > delta))
 			steal = delta;
 
-		rq->prev_steal_time_rq += steal;
+		rq->prev_steal_time_rq = prev_steal;
 		delta -= steal;
 	}
 #endif
-- 
2.39.5

[PATCH AUTOSEL 6.13 2/7] sched/deadline: Correctly account for allocated bandwidth during hotplug

[Sasha Levin]

From: Juri Lelli <juri.lelli@redhat.com>

[ Upstream commit d4742f6ed7ea6df56e381f82ba4532245fa1e561 ]

For hotplug operations, DEADLINE needs to check that there is still enough
bandwidth left after removing the CPU that is going offline. We however
fail to do so currently.

Restore the correct behavior by restructuring dl_bw_manage() a bit, so
that overflow conditions (not enough bandwidth left) are properly
checked. Also account for dl_server bandwidth, i.e. discount such
bandwidth in the calculation since NORMAL tasks will be anyway moved
away from the CPU as a result of the hotplug operation.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Tested-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20241114142810.794657-3-juri.lelli@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/sched/core.c     |  2 +-
 kernel/sched/deadline.c | 48 +++++++++++++++++++++++++++++++++--------
 kernel/sched/sched.h    |  2 +-
 3 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 296e77380318e..f823942c9e11a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8185,7 +8185,7 @@ static void cpuset_cpu_active(void)
 static int cpuset_cpu_inactive(unsigned int cpu)
 {
 	if (!cpuhp_tasks_frozen) {
-		int ret = dl_bw_check_overflow(cpu);
+		int ret = dl_bw_deactivate(cpu);
 
 		if (ret)
 			return ret;
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index d94f2ed6d1f46..b078014273d9e 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3453,29 +3453,31 @@ int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
 }
 
 enum dl_bw_request {
-	dl_bw_req_check_overflow = 0,
+	dl_bw_req_deactivate = 0,
 	dl_bw_req_alloc,
 	dl_bw_req_free
 };
 
 static int dl_bw_manage(enum dl_bw_request req, int cpu, u64 dl_bw)
 {
-	unsigned long flags;
+	unsigned long flags, cap;
 	struct dl_bw *dl_b;
 	bool overflow = 0;
+	u64 fair_server_bw = 0;
 
 	rcu_read_lock_sched();
 	dl_b = dl_bw_of(cpu);
 	raw_spin_lock_irqsave(&dl_b->lock, flags);
 
-	if (req == dl_bw_req_free) {
+	cap = dl_bw_capacity(cpu);
+	switch (req) {
+	case dl_bw_req_free:
 		__dl_sub(dl_b, dl_bw, dl_bw_cpus(cpu));
-	} else {
-		unsigned long cap = dl_bw_capacity(cpu);
-
+		break;
+	case dl_bw_req_alloc:
 		overflow = __dl_overflow(dl_b, cap, 0, dl_bw);
 
-		if (req == dl_bw_req_alloc && !overflow) {
+		if (!overflow) {
 			/*
 			 * We reserve space in the destination
 			 * root_domain, as we can't fail after this point.
@@ -3484,6 +3486,34 @@ static int dl_bw_manage(enum dl_bw_request req, int cpu, u64 dl_bw)
 			 */
 			__dl_add(dl_b, dl_bw, dl_bw_cpus(cpu));
 		}
+		break;
+	case dl_bw_req_deactivate:
+		/*
+		 * cpu is going offline and NORMAL tasks will be moved away
+		 * from it. We can thus discount dl_server bandwidth
+		 * contribution as it won't need to be servicing tasks after
+		 * the cpu is off.
+		 */
+		if (cpu_rq(cpu)->fair_server.dl_server)
+			fair_server_bw = cpu_rq(cpu)->fair_server.dl_bw;
+
+		/*
+		 * Not much to check if no DEADLINE bandwidth is present.
+		 * dl_servers we can discount, as tasks will be moved out the
+		 * offlined CPUs anyway.
+		 */
+		if (dl_b->total_bw - fair_server_bw > 0) {
+			/*
+			 * Leaving at least one CPU for DEADLINE tasks seems a
+			 * wise thing to do.
+			 */
+			if (dl_bw_cpus(cpu))
+				overflow = __dl_overflow(dl_b, cap, fair_server_bw, 0);
+			else
+				overflow = 1;
+		}
+
+		break;
 	}
 
 	raw_spin_unlock_irqrestore(&dl_b->lock, flags);
@@ -3492,9 +3522,9 @@ static int dl_bw_manage(enum dl_bw_request req, int cpu, u64 dl_bw)
 	return overflow ? -EBUSY : 0;
 }
 
-int dl_bw_check_overflow(int cpu)
+int dl_bw_deactivate(int cpu)
 {
-	return dl_bw_manage(dl_bw_req_check_overflow, cpu, 0);
+	return dl_bw_manage(dl_bw_req_deactivate, cpu, 0);
 }
 
 int dl_bw_alloc(int cpu, u64 dl_bw)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c5d67a43fe524..96d9bbba94acc 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -362,7 +362,7 @@ extern void __getparam_dl(struct task_struct *p, struct sched_attr *attr);
 extern bool __checkparam_dl(const struct sched_attr *attr);
 extern bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr);
 extern int  dl_cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
-extern int  dl_bw_check_overflow(int cpu);
+extern int  dl_bw_deactivate(int cpu);
 extern s64 dl_scaled_delta_exec(struct rq *rq, struct sched_dl_entity *dl_se, s64 delta_exec);
 /*
  * SCHED_DEADLINE supports servers (nested scheduling) with the following
-- 
2.39.5

[PATCH AUTOSEL 6.13 3/7] sched/deadline: Check bandwidth overflow earlier for hotplug

[Sasha Levin]

From: Juri Lelli <juri.lelli@redhat.com>

[ Upstream commit 53916d5fd3c0b658de3463439dd2b7ce765072cb ]

Currently we check for bandwidth overflow potentially due to hotplug
operations at the end of sched_cpu_deactivate(), after the cpu going
offline has already been removed from scheduling, active_mask, etc.
This can create issues for DEADLINE tasks, as there is a substantial
race window between the start of sched_cpu_deactivate() and the moment
we possibly decide to roll-back the operation if dl_bw_deactivate()
returns failure in cpuset_cpu_inactive(). An example is a throttled
task that sees its replenishment timer firing while the cpu it was
previously running on is considered offline, but before
dl_bw_deactivate() had a chance to say no and roll-back happened.

Fix this by directly calling dl_bw_deactivate() first thing in
sched_cpu_deactivate() and do the required calculation in the former
function considering the cpu passed as an argument as offline already.

By doing so we also simplify sched_cpu_deactivate(), as there is no need
anymore for any kind of roll-back if we fail early.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Tested-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/Zzc1DfPhbvqDDIJR@jlelli-thinkpadt14gen4.remote.csb
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/sched/core.c     | 22 +++++++---------------
 kernel/sched/deadline.c | 12 ++++++++++--
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f823942c9e11a..ed95861e9887c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8182,19 +8182,14 @@ static void cpuset_cpu_active(void)
 	cpuset_update_active_cpus();
 }
 
-static int cpuset_cpu_inactive(unsigned int cpu)
+static void cpuset_cpu_inactive(unsigned int cpu)
 {
 	if (!cpuhp_tasks_frozen) {
-		int ret = dl_bw_deactivate(cpu);
-
-		if (ret)
-			return ret;
 		cpuset_update_active_cpus();
 	} else {
 		num_cpus_frozen++;
 		partition_sched_domains(1, NULL, NULL);
 	}
-	return 0;
 }
 
 static inline void sched_smt_present_inc(int cpu)
@@ -8256,6 +8251,11 @@ int sched_cpu_deactivate(unsigned int cpu)
 	struct rq *rq = cpu_rq(cpu);
 	int ret;
 
+	ret = dl_bw_deactivate(cpu);
+
+	if (ret)
+		return ret;
+
 	/*
 	 * Remove CPU from nohz.idle_cpus_mask to prevent participating in
 	 * load balancing when not active
@@ -8301,15 +8301,7 @@ int sched_cpu_deactivate(unsigned int cpu)
 		return 0;
 
 	sched_update_numa(cpu, false);
-	ret = cpuset_cpu_inactive(cpu);
-	if (ret) {
-		sched_smt_present_inc(cpu);
-		sched_set_rq_online(rq, cpu);
-		balance_push_set(cpu, false);
-		set_cpu_active(cpu, true);
-		sched_update_numa(cpu, true);
-		return ret;
-	}
+	cpuset_cpu_inactive(cpu);
 	sched_domains_numa_masks_clear(cpu);
 	return 0;
 }
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index b078014273d9e..b6781ddea7650 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3488,6 +3488,13 @@ static int dl_bw_manage(enum dl_bw_request req, int cpu, u64 dl_bw)
 		}
 		break;
 	case dl_bw_req_deactivate:
+		/*
+		 * cpu is not off yet, but we need to do the math by
+		 * considering it off already (i.e., what would happen if we
+		 * turn cpu off?).
+		 */
+		cap -= arch_scale_cpu_capacity(cpu);
+
 		/*
 		 * cpu is going offline and NORMAL tasks will be moved away
 		 * from it. We can thus discount dl_server bandwidth
@@ -3505,9 +3512,10 @@ static int dl_bw_manage(enum dl_bw_request req, int cpu, u64 dl_bw)
 		if (dl_b->total_bw - fair_server_bw > 0) {
 			/*
 			 * Leaving at least one CPU for DEADLINE tasks seems a
-			 * wise thing to do.
+			 * wise thing to do. As said above, cpu is not offline
+			 * yet, so account for that.
 			 */
-			if (dl_bw_cpus(cpu))
+			if (dl_bw_cpus(cpu) - 1)
 				overflow = __dl_overflow(dl_b, cap, fair_server_bw, 0);
 			else
 				overflow = 1;
-- 
2.39.5

[PATCH AUTOSEL 6.13 4/7] x86: Convert unreachable() to BUG()

[Sasha Levin]

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 2190966fbc14ca2cd4ea76eefeb96a47d8e390df ]

Avoid unreachable() as it can (and will in the absence of UBSAN)
generate fallthrough code. Use BUG() so we get a UD2 trap (with
unreachable annotation).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20241128094312.028316261@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kernel/process.c | 2 +-
 arch/x86/kernel/reboot.c  | 2 +-
 arch/x86/kvm/svm/sev.c    | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index f63f8fd00a91f..15507e739c255 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -838,7 +838,7 @@ void __noreturn stop_this_cpu(void *dummy)
 #ifdef CONFIG_SMP
 	if (smp_ops.stop_this_cpu) {
 		smp_ops.stop_this_cpu();
-		unreachable();
+		BUG();
 	}
 #endif
 
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 615922838c510..dc1dd3f3e67fc 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -883,7 +883,7 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
 
 	if (smp_ops.stop_this_cpu) {
 		smp_ops.stop_this_cpu();
-		unreachable();
+		BUG();
 	}
 
 	/* Assume hlt works */
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 943bd074a5d37..fe6cc763fd518 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3820,7 +3820,7 @@ static int snp_begin_psc(struct vcpu_svm *svm, struct psc_buffer *psc)
 		goto next_range;
 	}
 
-	unreachable();
+	BUG();
 }
 
 static int __sev_snp_update_protected_guest_state(struct kvm_vcpu *vcpu)
-- 
2.39.5

[PATCH AUTOSEL 6.13 5/7] locking/ww_mutex/test: Use swap() macro

[Sasha Levin]

From: Thorsten Blum <thorsten.blum@toblux.com>

[ Upstream commit 0d3547df6934b8f9600630322799a2a76b4567d8 ]

Fixes the following Coccinelle/coccicheck warning reported by
swap.cocci:

  WARNING opportunity for swap()

Compile-tested only.

[Boqun: Add the report tags from Jiapeng and Abaci Robot [1].]

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reported-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=11531
Link: https://lore.kernel.org/r/20241025081455.55089-1-jiapeng.chong@linux.alibaba.com [1]
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20240731135850.81018-2-thorsten.blum@toblux.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/locking/test-ww_mutex.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 5d58b2c0ef98b..bcb1b9fea5880 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -404,7 +404,7 @@ static inline u32 prandom_u32_below(u32 ceil)
 static int *get_random_order(int count)
 {
 	int *order;
-	int n, r, tmp;
+	int n, r;
 
 	order = kmalloc_array(count, sizeof(*order), GFP_KERNEL);
 	if (!order)
@@ -415,11 +415,8 @@ static int *get_random_order(int count)
 
 	for (n = count - 1; n > 1; n--) {
 		r = prandom_u32_below(n + 1);
-		if (r != n) {
-			tmp = order[n];
-			order[n] = order[r];
-			order[r] = tmp;
-		}
+		if (r != n)
+			swap(order[n], order[r]);
 	}
 
 	return order;
-- 
2.39.5

[PATCH AUTOSEL 6.13 6/7] lockdep: Fix upper limit for LOCKDEP_*_BITS configs

[Sasha Levin]

From: Carlos Llamas <cmllamas@google.com>

[ Upstream commit e638072e61726cae363d48812815197a2a0e097f ]

Lockdep has a set of configs used to determine the size of the static
arrays that it uses. However, the upper limit that was initially setup
for these configs is too high (30 bit shift). This equates to several
GiB of static memory for individual symbols. Using such high values
leads to linker errors:

  $ make defconfig
  $ ./scripts/config -e PROVE_LOCKING --set-val LOCKDEP_BITS 30
  $ make olddefconfig all
  [...]
  ld: kernel image bigger than KERNEL_IMAGE_SIZE
  ld: section .bss VMA wraps around address space

Adjust the upper limits to the maximum values that avoid these issues.
The need for anything more, likely points to a problem elsewhere. Note
that LOCKDEP_CHAINS_BITS was intentionally left out as its upper limit
had a different symptom and has already been fixed [1].

Reported-by: J. R. Okajima <hooanon05g@gmail.com>
Closes: https://lore.kernel.org/all/30795.1620913191@jrobl/ [1]
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20241024183631.643450-2-cmllamas@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 lib/Kconfig.debug | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index f3d7237058793..bc725add84f46 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1504,7 +1504,7 @@ config LOCKDEP_SMALL
 config LOCKDEP_BITS
 	int "Bitsize for MAX_LOCKDEP_ENTRIES"
 	depends on LOCKDEP && !LOCKDEP_SMALL
-	range 10 30
+	range 10 24
 	default 15
 	help
 	  Try increasing this value if you hit "BUG: MAX_LOCKDEP_ENTRIES too low!" message.
@@ -1520,7 +1520,7 @@ config LOCKDEP_CHAINS_BITS
 config LOCKDEP_STACK_TRACE_BITS
 	int "Bitsize for MAX_STACK_TRACE_ENTRIES"
 	depends on LOCKDEP && !LOCKDEP_SMALL
-	range 10 30
+	range 10 26
 	default 19
 	help
 	  Try increasing this value if you hit "BUG: MAX_STACK_TRACE_ENTRIES too low!" message.
@@ -1528,7 +1528,7 @@ config LOCKDEP_STACK_TRACE_BITS
 config LOCKDEP_STACK_TRACE_HASH_BITS
 	int "Bitsize for STACK_TRACE_HASH_SIZE"
 	depends on LOCKDEP && !LOCKDEP_SMALL
-	range 10 30
+	range 10 26
 	default 14
 	help
 	  Try increasing this value if you need large STACK_TRACE_HASH_SIZE.
@@ -1536,7 +1536,7 @@ config LOCKDEP_STACK_TRACE_HASH_BITS
 config LOCKDEP_CIRCULAR_QUEUE_BITS
 	int "Bitsize for elements in circular_queue struct"
 	depends on LOCKDEP
-	range 10 30
+	range 10 26
 	default 12
 	help
 	  Try increasing this value if you hit "lockdep bfs error:-1" warning due to __cq_enqueue() failure.
-- 
2.39.5

[PATCH AUTOSEL 6.13 7/7] x86/amd_nb: Restrict init function to AMD-based systems

[Sasha Levin]

From: Yazen Ghannam <yazen.ghannam@amd.com>

[ Upstream commit bee9e840609cc67d0a7d82f22a2130fb7a0a766d ]

The code implicitly operates on AMD-based systems by matching on PCI
IDs. However, the use of these IDs is going away.

Add an explicit CPU vendor check instead of relying on PCI IDs.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241206161210.163701-3-yazen.ghannam@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kernel/amd_nb.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 9fe9972d2071b..37b8244899d89 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -582,6 +582,10 @@ static __init void fix_erratum_688(void)
 
 static __init int init_amd_nbs(void)
 {
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
+	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
+		return 0;
+
 	amd_cache_northbridges();
 	amd_cache_gart();
 
-- 
2.39.5