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From c0d6740c1219f23f0b9a996f02c1ae9cf824b0b3 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Thu, 6 Dec 2018 17:12:28 +0000
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Subject: [PATCH 03/15] qcow2: Fix Coverity warning when calculating the
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refcount cache size
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20181206171240.5674-4-kwolf@redhat.com>
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Patchwork-id: 83295
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O-Subject: [RHEL-8.0 qemu-kvm PATCH 03/15] qcow2: Fix Coverity warning when calculating the refcount cache size
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Bugzilla: 1656507
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Alberto Garcia <berto@igalia.com>
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MIN_REFCOUNT_CACHE_SIZE is 4 and the cluster size is guaranteed to be
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at most 2MB, so the minimum refcount cache size (in bytes) is always
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going to fit in a 32-bit integer.
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Coverity doesn't know that, and since we're storing the result in a
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uint64_t (*refcount_cache_size) it thinks that we need the 64 bits and
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that we probably want to do a 64-bit multiplication to prevent the
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result from being truncated.
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This is a false positive in this case, but it's a fair warning.
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We could do a 64-bit multiplication to get rid of it, but since we
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know that a 32-bit variable is enough to store this value let's simply
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reuse min_refcount_cache, make it a normal int and stop doing casts.
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Reported-by: Peter Maydell <peter.maydell@linaro.org>
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Signed-off-by: Alberto Garcia <berto@igalia.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 7af5eea9b34ffb7a9a9fc25ba71998a02b76e159)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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block/qcow2.c | 5 ++---
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1 file changed, 2 insertions(+), 3 deletions(-)
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diff --git a/block/qcow2.c b/block/qcow2.c
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index 4b65e4c..a0f7234 100644
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--- a/block/qcow2.c
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+++ b/block/qcow2.c
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@@ -775,6 +775,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
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BDRVQcow2State *s = bs->opaque;
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uint64_t combined_cache_size;
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bool l2_cache_size_set, refcount_cache_size_set, combined_cache_size_set;
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+ int min_refcount_cache = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;
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combined_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_CACHE_SIZE);
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l2_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_L2_CACHE_SIZE);
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@@ -811,8 +812,6 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
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} else {
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uint64_t virtual_disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
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uint64_t max_l2_cache = virtual_disk_size / (s->cluster_size / 8);
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- uint64_t min_refcount_cache =
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- (uint64_t) MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;
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/* Assign as much memory as possible to the L2 cache, and
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* use the remainder for the refcount cache */
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@@ -832,7 +831,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
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* s->cluster_size);
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}
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if (!refcount_cache_size_set) {
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- *refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;
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+ *refcount_cache_size = min_refcount_cache;
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}
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}
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--
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1.8.3.1
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