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From: Usama Arif <usama.arif@bytedance.com>
To: dwmw2@infradead.org, tglx@linutronix.de
Cc: mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
	hpa@zytor.com, x86@kernel.org, pbonzini@redhat.com,
	paulmck@kernel.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de,
	hewenliang4@huawei.com, thomas.lendacky@amd.com,
	seanjc@google.com, pmenzel@molgen.mpg.de,
	fam.zheng@bytedance.com, punit.agrawal@bytedance.com,
	simon.evans@bytedance.com, liangma@liangbit.com,
	David Woodhouse <dwmw@amazon.co.uk>,
	Usama Arif <usama.arif@bytedance.com>
Subject: [PATCH 4/9] x86/smpboot: Reference count on smpboot_setup_warm_reset_vector()
Date: Wed,  1 Feb 2023 20:43:33 +0000	[thread overview]
Message-ID: <20230201204338.1337562-5-usama.arif@bytedance.com> (raw)
In-Reply-To: <20230201204338.1337562-1-usama.arif@bytedance.com>

From: David Woodhouse <dwmw@amazon.co.uk>

If we want to do parallel CPU bringup, we're going to need to set this up
and leave it until all CPUs are done. Might as well use the RTC spinlock
to protect the refcount, as we need to take it anyway.

[Usama Arif: fixed rebase conflict]
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
---
 arch/x86/kernel/smpboot.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index dd2f61c3797f..2d5014752dc4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -120,17 +120,22 @@ int arch_update_cpu_topology(void)
 	return retval;
 }
 
+
+static unsigned int smpboot_warm_reset_vector_count;
+
 static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
 {
 	unsigned long flags;
 
 	spin_lock_irqsave(&rtc_lock, flags);
-	CMOS_WRITE(0xa, 0xf);
+	if (!smpboot_warm_reset_vector_count++) {
+		CMOS_WRITE(0xa, 0xf);
+		*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_HIGH)) =
+			start_eip >> 4;
+		*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =
+			start_eip & 0xf;
+	}
 	spin_unlock_irqrestore(&rtc_lock, flags);
-	*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_HIGH)) =
-							start_eip >> 4;
-	*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =
-							start_eip & 0xf;
 }
 
 static inline void smpboot_restore_warm_reset_vector(void)
@@ -142,10 +147,12 @@ static inline void smpboot_restore_warm_reset_vector(void)
 	 * to default values.
 	 */
 	spin_lock_irqsave(&rtc_lock, flags);
-	CMOS_WRITE(0, 0xf);
+	if (!--smpboot_warm_reset_vector_count) {
+		CMOS_WRITE(0, 0xf);
+		*((volatile u32 *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) = 0;
+	}
 	spin_unlock_irqrestore(&rtc_lock, flags);
 
-	*((volatile u32 *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) = 0;
 }
 
 /*
-- 
2.25.1


  parent reply	other threads:[~2023-02-01 20:45 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-01 20:43 [PATCH 0/9] Parallel CPU bringup for x86_64 Usama Arif
2023-02-01 20:43 ` [PATCH 1/9] x86/apic/x2apic: Fix parallel handling of cluster_mask Usama Arif
2023-02-01 20:43 ` [PATCH 2/9] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h> Usama Arif
2023-02-01 20:43 ` [PATCH 3/9] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU Usama Arif
2023-02-01 20:43 ` Usama Arif [this message]
2023-02-01 20:43 ` [PATCH 5/9] x86/smpboot: Split up native_cpu_up into separate phases and document them Usama Arif
2023-02-01 20:43 ` [PATCH 6/9] x86/smpboot: Support parallel startup of secondary CPUs Usama Arif
2023-02-01 20:43 ` [PATCH 7/9] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Usama Arif
2023-02-01 20:43 ` [PATCH 8/9] x86/mtrr: Avoid repeated save of MTRRs on boot-time CPU bringup Usama Arif
2023-02-01 20:43 ` [PATCH 9/9] x86/smpboot: Serialize topology updates for secondary bringup Usama Arif
2023-02-02 10:02 ` [PATCH 0/9] Parallel CPU bringup for x86_64 David Woodhouse
2023-02-02 21:59   ` Usama Arif

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