| Message ID | 20190618112341.513-5-anthony.perard@citrix.com |
|---|---|
| State | New |
| Headers | show |
| Series | Fix build of Xen support + cleanup | expand |
On 6/18/19 1:23 PM, Anthony PERARD wrote: > Avoid using a variable length array. > > We allocate the `dirty_bitmap' buffer only once when we start tracking > for dirty bits. > Suggested-by: Paul Durrant <Paul.Durrant@citrix.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> > 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); > } >
> -----Original Message----- > From: Anthony PERARD [mailto:anthony.perard@citrix.com] > Sent: 18 June 2019 12:24 > To: qemu-devel@nongnu.org > Cc: Anthony Perard <anthony.perard@citrix.com>; Paul Durrant <Paul.Durrant@citrix.com>; Stefano > Stabellini <sstabellini@kernel.org>; xen-devel@lists.xenproject.org > Subject: [PATCH v2 4/4] xen: Avoid VLA > > 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> Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
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); }
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(-)