linux-kernel - [PATCH 3/4] reduce stack usage in kvm_arch_vcpu

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Date:	Mon,  4 Aug 2008 11:31:36 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...o.co.il>
Cc:	kvm-devel <kvm@...r.kernel.org>,
	Anthony Liguori <aliguori@...ibm.com>,
	linux-kernel@...r.kernel.org, Dave Hansen <dave@...ux.vnet.ibm.com>
Subject: [PATCH 3/4] reduce stack usage in kvm_arch_vcpu_ioctl()

This time it is kvm_arch_vcpu_ioctl().  Use dynamic
allocations to reduce its stack usage.

Signed-off-by: Dave Hansen <dave@...ux.vnet.ibm.com>
---
 arch/x86/kvm/x86.c |   20 +++++++++++++-------
 1 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9d77da1..3bbd123 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1303,13 +1303,16 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	struct kvm_vcpu *vcpu = filp->private_data;
 	void __user *argp = (void __user *)arg;
 	int r;
+	struct kvm_lapic_state *lapic = NULL;
 
 	switch (ioctl) {
 	case KVM_GET_LAPIC: {
-		struct kvm_lapic_state lapic;
+		lapic = kzalloc(sizeof(struct kvm_lapic_state), GFP_KERNEL);
 
-		memset(&lapic, 0, sizeof lapic);
-		r = kvm_vcpu_ioctl_get_lapic(vcpu, &lapic);
+		r = -ENOMEM;
+		if (!lapic)
+			goto out;
+		r = kvm_vcpu_ioctl_get_lapic(vcpu, lapic);
 		if (r)
 			goto out;
 		r = -EFAULT;
@@ -1319,12 +1322,14 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		break;
 	}
 	case KVM_SET_LAPIC: {
-		struct kvm_lapic_state lapic;
-
+		lapic = kmalloc(sizeof(struct kvm_lapic_state), GFP_KERNEL);
+		r = -ENOMEM;
+		if (!lapic)
+			goto out;
 		r = -EFAULT;
-		if (copy_from_user(&lapic, argp, sizeof lapic))
+		if (copy_from_user(lapic, argp, sizeof(struct kvm_lapic_state)))
 			goto out;
-		r = kvm_vcpu_ioctl_set_lapic(vcpu, &lapic);;
+		r = kvm_vcpu_ioctl_set_lapic(vcpu, lapic);
 		if (r)
 			goto out;
 		r = 0;
@@ -1422,6 +1427,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		r = -EINVAL;
 	}
 out:
+	kfree(lapic);
 	return r;
 }
 
-- 
1.5.4.3

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