linux-kernel - [tip:core/smp] xen: Add xen_pin_vcpu() to support calling functions on a dedicated pCPU

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Date:   Mon, 5 Sep 2016 06:29:14 -0700
From:   tip-bot for Juergen Gross <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, linux-kernel@...r.kernel.org, mingo@...nel.org,
        tglx@...utronix.de, jgross@...e.com, peterz@...radead.org,
        david.vrabel@...rix.com, torvalds@...ux-foundation.org
Subject: [tip:core/smp] xen: Add xen_pin_vcpu() to support calling functions
 on a dedicated pCPU

Commit-ID:  99bc67536d04bcb9133546284acfb15d033b8bfe
Gitweb:     http://git.kernel.org/tip/99bc67536d04bcb9133546284acfb15d033b8bfe
Author:     Juergen Gross <jgross@...e.com>
AuthorDate: Mon, 29 Aug 2016 08:48:45 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 5 Sep 2016 13:52:40 +0200

xen: Add xen_pin_vcpu() to support calling functions on a dedicated pCPU

Some hardware models (e.g. Dell Studio 1555 laptops) require calls to
the firmware to be issued on CPU 0 only. As Dom0 might have to use
these calls, add xen_pin_vcpu() to achieve this functionality.

In case either the domain doesn't have the privilege to make the
related hypercall or the hypervisor isn't supporting it, issue a
warning once and disable further pinning attempts.

Signed-off-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: David Vrabel <david.vrabel@...rix.com>
Cc: Douglas_Warzecha@...l.com
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: akataria@...are.com
Cc: boris.ostrovsky@...cle.com
Cc: chrisw@...s-sol.org
Cc: hpa@...or.com
Cc: jdelvare@...e.com
Cc: jeremy@...p.org
Cc: linux@...ck-us.net
Cc: pali.rohar@...il.com
Cc: rusty@...tcorp.com.au
Cc: virtualization@...ts.linux-foundation.org
Cc: xen-devel@...ts.xenproject.org
Link: http://lkml.kernel.org/r/1472453327-19050-5-git-send-email-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/xen/enlighten.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b86ebb1..bc9aaba 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1925,6 +1925,45 @@ static void xen_set_cpu_features(struct cpuinfo_x86 *c)
 	}
 }
 
+static void xen_pin_vcpu(int cpu)
+{
+	static bool disable_pinning;
+	struct sched_pin_override pin_override;
+	int ret;
+
+	if (disable_pinning)
+		return;
+
+	pin_override.pcpu = cpu;
+	ret = HYPERVISOR_sched_op(SCHEDOP_pin_override, &pin_override);
+
+	/* Ignore errors when removing override. */
+	if (cpu < 0)
+		return;
+
+	switch (ret) {
+	case -ENOSYS:
+		pr_warn("Unable to pin on physical cpu %d. In case of problems consider vcpu pinning.\n",
+			cpu);
+		disable_pinning = true;
+		break;
+	case -EPERM:
+		WARN(1, "Trying to pin vcpu without having privilege to do so\n");
+		disable_pinning = true;
+		break;
+	case -EINVAL:
+	case -EBUSY:
+		pr_warn("Physical cpu %d not available for pinning. Check Xen cpu configuration.\n",
+			cpu);
+		break;
+	case 0:
+		break;
+	default:
+		WARN(1, "rc %d while trying to pin vcpu\n", ret);
+		disable_pinning = true;
+	}
+}
+
 const struct hypervisor_x86 x86_hyper_xen = {
 	.name			= "Xen",
 	.detect			= xen_platform,
@@ -1933,6 +1972,7 @@ const struct hypervisor_x86 x86_hyper_xen = {
 #endif
 	.x2apic_available	= xen_x2apic_para_available,
 	.set_cpu_features       = xen_set_cpu_features,
+	.pin_vcpu               = xen_pin_vcpu,
 };
 EXPORT_SYMBOL(x86_hyper_xen);