[PATCH v2] PC, KVM, CMA: Fix regression caused by wrong get_order() use

Alexey Kardashevskiy aik at ozlabs.ru
Thu Aug 14 15:03:07 EST 2014

fc95ca7284bc54953165cba76c3228bd2cdb9591 claims that there is no
functional change but this is not true as it calls get_order() (which
takes bytes) where it should have called ilog2() and the kernel stops
on VM_BUG_ON().

This replaces get_order() with order_base_2() (round-up version of ilog2).

Suggested-by: Paul Mackerras <paulus at samba.org>
Cc: Alexander Graf <agraf at suse.de>
Cc: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim at lge.com>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>

* s/ilog2/order_base_2/
* removed cc: <stable at vger.kernel.org> as I got wrong impression that v3.16 is

 arch/powerpc/kvm/book3s_hv_builtin.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
index 329d7fd..b9615ba 100644
--- a/arch/powerpc/kvm/book3s_hv_builtin.c
+++ b/arch/powerpc/kvm/book3s_hv_builtin.c
@@ -101,7 +101,7 @@ struct kvm_rma_info *kvm_alloc_rma()
 	ri = kmalloc(sizeof(struct kvm_rma_info), GFP_KERNEL);
 	if (!ri)
 		return NULL;
-	page = cma_alloc(kvm_cma, kvm_rma_pages, get_order(kvm_rma_pages));
+	page = cma_alloc(kvm_cma, kvm_rma_pages, order_base_2(kvm_rma_pages));
 	if (!page)
 		goto err_out;
 	atomic_set(&ri->use_count, 1);
@@ -135,12 +135,12 @@ struct page *kvm_alloc_hpt(unsigned long nr_pages)
 	unsigned long align_pages = HPT_ALIGN_PAGES;
-	VM_BUG_ON(get_order(nr_pages) < KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);
+	VM_BUG_ON(order_base_2(nr_pages) < KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);
 	/* Old CPUs require HPT aligned on a multiple of its size */
 	if (!cpu_has_feature(CPU_FTR_ARCH_206))
 		align_pages = nr_pages;
-	return cma_alloc(kvm_cma, nr_pages, get_order(align_pages));
+	return cma_alloc(kvm_cma, nr_pages, order_base_2(align_pages));

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