[patch] kvm: fix GFP_KERNEL alloc in atomic section bug

Subject: [patch] kvm: fix GFP_KERNEL alloc in atomic section bug
From: Ingo Molnar <mingo@xxxxxxx>

KVM does kmalloc() in an atomic section while having preemption disabled 
via vcpu_load(). Fix this by moving the ->*_msr setup from the 
vcpu_setup method to the vcpu_create method.

(This is also a small speedup for setting up a vcpu, which can in theory 
be more frequent than the vcpu_create method).

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 drivers/kvm/vmx.c |   32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

Index: linux/drivers/kvm/vmx.c
===================================================================
--- linux.orig/drivers/kvm/vmx.c
+++ linux/drivers/kvm/vmx.c
@@ -1094,14 +1094,6 @@ static int vmx_vcpu_setup(struct kvm_vcp
        rdmsrl(MSR_IA32_SYSENTER_EIP, a);
        vmcs_writel(HOST_IA32_SYSENTER_EIP, a);   /* 22.2.3 */
 
-       ret = -ENOMEM;
-       vcpu->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL);
-       if (!vcpu->guest_msrs)
-               goto out;
-       vcpu->host_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL);
-       if (!vcpu->host_msrs)
-               goto out_free_guest_msrs;
-
        for (i = 0; i < NR_VMX_MSR; ++i) {
                u32 index = vmx_msr_index[i];
                u32 data_low, data_high;
@@ -1155,8 +1147,6 @@ static int vmx_vcpu_setup(struct kvm_vcp
 
        return 0;
 
-out_free_guest_msrs:
-       kfree(vcpu->guest_msrs);
 out:
        return ret;
 }
@@ -1906,13 +1896,33 @@ static int vmx_create_vcpu(struct kvm_vc
 {
        struct vmcs *vmcs;
 
+       vcpu->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL);
+       if (!vcpu->guest_msrs)
+               return -ENOMEM;
+
+       vcpu->host_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL);
+       if (!vcpu->host_msrs)
+               goto out_free_guest_msrs;
+
        vmcs = alloc_vmcs();
        if (!vmcs)
-               return -ENOMEM;
+               goto out_free_msrs;
+
        vmcs_clear(vmcs);
        vcpu->vmcs = vmcs;
        vcpu->launched = 0;
+
        return 0;
+
+out_free_msrs:
+       kfree(vcpu->host_msrs);
+       vcpu->host_msrs = NULL;
+
+out_free_guest_msrs:
+       kfree(vcpu->guest_msrs);
+       vcpu->guest_msrs = NULL;
+
+       return -ENOMEM;
 }
 
 static struct kvm_arch_ops vmx_arch_ops = {


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