commit 10589a4699bb978c781ce73bbae8ca942c5250c9
author Marcelo Tosatti <mtosatti@redhat.com> Thu Dec 20 19:18:22 2007 -0500
committer Avi Kivity <avi@qumranet.com> Wed Jan 30 18:01:20 2008 +0200
tree 5585ed87fff0a2ba259fcc6f998022481da75f68
parent 774ead3ad9bcbc05ef6aaebb9bdf8b4c3126923b

KVM: MMU: Concurrent guest walkers

Do not hold kvm->lock mutex across the entire pagefault code,
only acquire it in places where it is necessary, such as mmu
hash list, active list, rmap and parent pte handling.

Allow concurrent guest walkers by switching walk_addr() to use
mmap_sem in read-mode.

And get rid of the lockless __gfn_to_page.

[avi: move kvm_mmu_pte_write() locking inside the function]
[avi: add locking for real mode]
[avi: fix cmpxchg locking]

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/vmx.c

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d1167fc..c39493f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1432,27 +1432,34 @@
 {
 	gfn_t fn = rmode_tss_base(kvm) >> PAGE_SHIFT;
 	u16 data = 0;
+	int ret = 0;
 	int r;
 
+	down_read(&current->mm->mmap_sem);
 	r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE);
 	if (r < 0)
-		return 0;
+		goto out;
 	data = TSS_BASE_SIZE + TSS_REDIRECTION_SIZE;
 	r = kvm_write_guest_page(kvm, fn++, &data, 0x66, sizeof(u16));
 	if (r < 0)
-		return 0;
+		goto out;
 	r = kvm_clear_guest_page(kvm, fn++, 0, PAGE_SIZE);
 	if (r < 0)
-		return 0;
+		goto out;
 	r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE);
 	if (r < 0)
-		return 0;
+		goto out;
 	data = ~0;
-	r = kvm_write_guest_page(kvm, fn, &data, RMODE_TSS_SIZE - 2 * PAGE_SIZE - 1,
-			sizeof(u8));
+	r = kvm_write_guest_page(kvm, fn, &data,
+				 RMODE_TSS_SIZE - 2 * PAGE_SIZE - 1,
+				 sizeof(u8));
 	if (r < 0)
-		return 0;
-	return 1;
+		goto out;
+
+	ret = 1;
+out:
+	up_read(&current->mm->mmap_sem);
+	return ret;
 }
 
 static void seg_setup(int seg)
@@ -1471,6 +1478,7 @@
 	int r = 0;
 
 	mutex_lock(&kvm->lock);
+	down_write(&current->mm->mmap_sem);
 	if (kvm->arch.apic_access_page)
 		goto out;
 	kvm_userspace_mem.slot = APIC_ACCESS_PAGE_PRIVATE_MEMSLOT;
@@ -1482,6 +1490,7 @@
 		goto out;
 	kvm->arch.apic_access_page = gfn_to_page(kvm, 0xfee00);
 out:
+	up_write(&current->mm->mmap_sem);
 	mutex_unlock(&kvm->lock);
 	return r;
 }