[PATCH v6 09/21] KVM: s390: vsie: Replace radix_tree with xarray addr_to_page

[Christoph Schlameuss <schlameuss@linux.ibm.com>]

The underlying implementation of radix_tree is xarray since v4.20.
Changing to the xarray API directly relaxes some of the locking
obligations and provides more symmetry with the next vsie changes in
the series.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host_s390.h |  2 +-
 arch/s390/kvm/s390/vsie.c             | 40 ++++++++++++++---------------------
 2 files changed, 17 insertions(+), 25 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host_s390.h b/arch/s390/include/asm/kvm_host_s390.h
index 6fdac144ca3a..82bfcc2bec74 100644
--- a/arch/s390/include/asm/kvm_host_s390.h
+++ b/arch/s390/include/asm/kvm_host_s390.h
@@ -575,7 +575,7 @@ struct vsie_page;
 
 struct kvm_s390_vsie {
 	struct mutex mutex;
-	struct radix_tree_root addr_to_page;
+	struct xarray addr_to_page;
 	int page_count;
 	int next;
 	struct vsie_page *pages[KVM_MAX_VCPUS];
diff --git a/arch/s390/kvm/s390/vsie.c b/arch/s390/kvm/s390/vsie.c
index e7005bade757..75676f493ab2 100644
--- a/arch/s390/kvm/s390/vsie.c
+++ b/arch/s390/kvm/s390/vsie.c
@@ -56,8 +56,7 @@ struct vsie_page {
 	gpa_t sdnx_gpa;				/* 0x0250 */
 	/*
 	 * guest address of the original SCB. Remains set for free vsie
-	 * pages, so we can properly look them up in our addr_to_page
-	 * radix tree.
+	 * pages, so we can properly look them up in our addr_to_page map.
 	 */
 	gpa_t scb_gpa;				/* 0x0258 */
 	/* the shadow gmap in use by the vsie_page */
@@ -1532,19 +1531,15 @@ static struct vsie_page *get_vsie_page(struct kvm *kvm, unsigned long addr)
 	struct vsie_page *vsie_page;
 	int nr_vcpus;
 
-	rcu_read_lock();
-	vsie_page = radix_tree_lookup(&kvm->arch.vsie.addr_to_page, addr >> SCB_ALIGNMENT_SHIFT);
-	rcu_read_unlock();
-	if (vsie_page) {
-		if (try_get_vsie_page(vsie_page)) {
-			if (vsie_page->scb_gpa == addr)
-				return vsie_page;
-			/*
-			 * We raced with someone reusing + putting this vsie
-			 * page before we grabbed it.
-			 */
-			put_vsie_page(vsie_page);
-		}
+	vsie_page = xa_load(&kvm->arch.vsie.addr_to_page, addr >> SCB_ALIGNMENT_SHIFT);
+	if (vsie_page && try_get_vsie_page(vsie_page)) {
+		if (vsie_page->scb_gpa == addr)
+			return vsie_page;
+		/*
+		 * We raced with someone reusing + putting this vsie
+		 * page before we grabbed it.
+		 */
+		put_vsie_page(vsie_page);
 	}
 
 	/*
@@ -1573,15 +1568,15 @@ static struct vsie_page *get_vsie_page(struct kvm *kvm, unsigned long addr)
 			kvm->arch.vsie.next %= nr_vcpus;
 		}
 		if (vsie_page->scb_gpa != ULONG_MAX)
-			radix_tree_delete(&kvm->arch.vsie.addr_to_page,
-					  vsie_page->scb_gpa >> SCB_ALIGNMENT_SHIFT);
+			xa_erase(&kvm->arch.vsie.addr_to_page,
+				 vsie_page->scb_gpa >> SCB_ALIGNMENT_SHIFT);
 		/* Mark it as invalid until it resides in the tree. */
 		vsie_page->scb_gpa = ULONG_MAX;
 	}
 
 	/* Double use of the same address or allocation failure. */
-	if (radix_tree_insert(&kvm->arch.vsie.addr_to_page, addr >> SCB_ALIGNMENT_SHIFT,
-			      vsie_page)) {
+	if (xa_insert(&kvm->arch.vsie.addr_to_page, addr >> SCB_ALIGNMENT_SHIFT, vsie_page,
+		      GFP_KERNEL_ACCOUNT)) {
 		put_vsie_page(vsie_page);
 		mutex_unlock(&kvm->arch.vsie.mutex);
 		return NULL;
@@ -1660,7 +1655,7 @@ int kvm_s390_handle_vsie(struct kvm_vcpu *vcpu)
 void kvm_s390_vsie_init(struct kvm *kvm)
 {
 	mutex_init(&kvm->arch.vsie.mutex);
-	INIT_RADIX_TREE(&kvm->arch.vsie.addr_to_page, GFP_KERNEL_ACCOUNT);
+	xa_init_flags(&kvm->arch.vsie.addr_to_page, XA_FLAGS_ACCOUNT);
 }
 
 /* Destroy the vsie data structures. To be called when a vm is destroyed. */
@@ -1676,12 +1671,9 @@ void kvm_s390_vsie_destroy(struct kvm *kvm)
 			if (vsie_page->gmap_cache.gmap)
 				release_gmap_shadow(vsie_page);
 		kvm->arch.vsie.pages[i] = NULL;
-		/* free the radix tree entry */
-		if (vsie_page->scb_gpa != ULONG_MAX)
-			radix_tree_delete(&kvm->arch.vsie.addr_to_page,
-					  vsie_page->scb_gpa >> SCB_ALIGNMENT_SHIFT);
 		free_vsie_page(vsie_page);
 	}
+	xa_destroy(&kvm->arch.vsie.addr_to_page);
 	kvm->arch.vsie.page_count = 0;
 	mutex_unlock(&kvm->arch.vsie.mutex);
 }

-- 
2.55.0