From: Anthony PERARD <anthony.perard@citrix.com>
To: <qemu-devel@nongnu.org>
Cc: Anthony PERARD <anthony.perard@citrix.com>,
xen-devel@lists.xenproject.org,
Paul Durrant <paul.durrant@citrix.com>,
Stefano Stabellini <sstabellini@kernel.org>
Subject: [Xen-devel] [PATCH v2 4/4] xen: Avoid VLA
Date: Tue, 18 Jun 2019 12:23:41 +0100 [thread overview]
Message-ID: <20190618112341.513-5-anthony.perard@citrix.com> (raw)
In-Reply-To: <20190618112341.513-1-anthony.perard@citrix.com>
Avoid using a variable length array.
We allocate the `dirty_bitmap' buffer only once when we start tracking
for dirty bits.
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
Notes:
v2:
- Allocate the bitmap buffer only once when we start tracking dirty bits.
(instead of at every function call)
Was suggested by Peter here:
<CAFEAcA88+A2oCkQnxKDEdpmfCZSmPzWMBg01wDDV68bMZoY5Jg@mail.gmail.com>
"should we try to stop using variable length arrays?"
hw/i386/xen/xen-hvm.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index ae3deb4ef3..469f1260a4 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -119,6 +119,8 @@ typedef struct XenIOState {
DeviceListener device_listener;
hwaddr free_phys_offset;
const XenPhysmap *log_for_dirtybit;
+ /* Buffer used by xen_sync_dirty_bitmap */
+ unsigned long *dirty_bitmap;
Notifier exit;
Notifier suspend;
@@ -464,6 +466,8 @@ static int xen_remove_from_physmap(XenIOState *state,
QLIST_REMOVE(physmap, list);
if (state->log_for_dirtybit == physmap) {
state->log_for_dirtybit = NULL;
+ g_free(state->dirty_bitmap);
+ state->dirty_bitmap = NULL;
}
g_free(physmap);
@@ -614,7 +618,7 @@ static void xen_sync_dirty_bitmap(XenIOState *state,
{
hwaddr npages = size >> TARGET_PAGE_BITS;
const int width = sizeof(unsigned long) * 8;
- unsigned long bitmap[DIV_ROUND_UP(npages, width)];
+ size_t bitmap_size = DIV_ROUND_UP(npages, width);
int rc, i, j;
const XenPhysmap *physmap = NULL;
@@ -626,13 +630,14 @@ static void xen_sync_dirty_bitmap(XenIOState *state,
if (state->log_for_dirtybit == NULL) {
state->log_for_dirtybit = physmap;
+ state->dirty_bitmap = g_new(unsigned long, bitmap_size);
} else if (state->log_for_dirtybit != physmap) {
/* Only one range for dirty bitmap can be tracked. */
return;
}
rc = xen_track_dirty_vram(xen_domid, start_addr >> TARGET_PAGE_BITS,
- npages, bitmap);
+ npages, state->dirty_bitmap);
if (rc < 0) {
#ifndef ENODATA
#define ENODATA ENOENT
@@ -646,8 +651,8 @@ static void xen_sync_dirty_bitmap(XenIOState *state,
return;
}
- for (i = 0; i < ARRAY_SIZE(bitmap); i++) {
- unsigned long map = bitmap[i];
+ for (i = 0; i < bitmap_size; i++) {
+ unsigned long map = state->dirty_bitmap[i];
while (map != 0) {
j = ctzl(map);
map &= ~(1ul << j);
@@ -677,6 +682,8 @@ static void xen_log_stop(MemoryListener *listener, MemoryRegionSection *section,
if (old & ~new & (1 << DIRTY_MEMORY_VGA)) {
state->log_for_dirtybit = NULL;
+ g_free(state->dirty_bitmap);
+ state->dirty_bitmap = NULL;
/* Disable dirty bit tracking */
xen_track_dirty_vram(xen_domid, 0, 0, NULL);
}
--
Anthony PERARD
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Xen-devel@lists.xenproject.org
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next prev parent reply other threads:[~2019-06-18 11:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-18 11:23 [Xen-devel] [PATCH v2 0/4] Fix build of Xen support + cleanup Anthony PERARD
2019-06-18 11:23 ` [Xen-devel] [PATCH v2 1/4] xen: Fix build with public headers Anthony PERARD
2019-06-18 12:14 ` [Xen-devel] [Qemu-devel] " Daniel P. Berrangé
2019-06-20 14:44 ` Anthony PERARD
2019-06-18 11:23 ` [Xen-devel] [PATCH v2 2/4] xen: Import other xen/io/*.h Anthony PERARD
2019-06-18 11:23 ` [Xen-devel] [PATCH v2 3/4] xen: Drop includes of xen/hvm/params.h Anthony PERARD
2019-06-18 11:51 ` Paul Durrant
2019-06-18 11:23 ` Anthony PERARD [this message]
2019-06-18 11:35 ` [Xen-devel] [Qemu-devel] [PATCH v2 4/4] xen: Avoid VLA Philippe Mathieu-Daudé
2019-06-18 11:52 ` [Xen-devel] " Paul Durrant
2019-06-18 12:00 ` [Xen-devel] [PATCH v2 0/4] Fix build of Xen support + cleanup no-reply
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