Re: [Qemu-devel] [PATCH] exec-obsolete: fix length handling

[Avi Kivity <avi@redhat.com>]

On 01/29/2012 03:16 PM, Blue Swirl wrote:
> On Sun, Jan 29, 2012 at 12:08, Avi Kivity <avi@redhat.com> wrote:
> > On 01/28/2012 08:13 PM, Blue Swirl wrote:
> >> Fix suspend/resume broken by off-by-one error in
> >> 59abb06198ee9471e29c970f294eae80c0b39be1.
> >>
> >> Adjust the loop so that it handles correctly the case
> >> start = (ram_addr_t)-TARGET_PAGE_SIZE, length = TARGET_PAGE_SIZE.
> >>
> >> Reported-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> >> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
> >> ---
> >>  exec-obsolete.h |   10 ++++------
> >>  1 files changed, 4 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/exec-obsolete.h b/exec-obsolete.h
> >> index 03cf35e..1bba970 100644
> >> --- a/exec-obsolete.h
> >> +++ b/exec-obsolete.h
> >> @@ -81,11 +81,10 @@ static inline void
> >> cpu_physical_memory_set_dirty_range(ram_addr_t start,
> >>                                                         int dirty_flags)
> >>  {
> >>      uint8_t *p;
> >> -    ram_addr_t addr, end;
> >> +    ram_addr_t cur;
> >>
> >> -    end = start + length;
> >>      p = ram_list.phys_dirty + (start >> TARGET_PAGE_BITS);
> >> -    for (addr = start; addr <= end; addr += TARGET_PAGE_SIZE) {
> >> +    for (cur = 0; cur < length; cur += TARGET_PAGE_SIZE) {
> >>          *p++ |= dirty_flags;
> >>      }
> >
> > I think this is still wrong - if length == 2 it will iterate once, but
> > we need two iterations if start == 0xfff.
>
> Yes, tricky. We could do something like
> for (cur = start & TARGET_PAGE_MASK; cur < length; cur += TARGET_PAGE_SIZE) {
> but I'll send a new patch with just s/<=/</.

That's broken too.

I have:

     uint8_t *p;
     ram_addr_t addr, end;
 
-    end = start + length;
+    end = (start + length - 1) | (TARGET_PAGE_SIZE - 1);
+    start &= TARGET_PAGE_MASK;
     p = ram_list.phys_dirty + (start >> TARGET_PAGE_BITS);
     for (addr = start; addr <= end; addr += TARGET_PAGE_SIZE) {
         *p++ |= dirty_flags;
@@ -98,7 +99,8 @@ static inline void
cpu_physical_memory_mask_dirty_range(ram_addr_t start,
     uint8_t *p;
     ram_addr_t addr, end;
 
-    end = start + length;
+    end = (start + length - 1) | (TARGET_PAGE_SIZE - 1);
+    start &= TARGET_PAGE_MASK;
     mask = ~dirty_flags;
     p = ram_list.phys_dirty + (start >> TARGET_PAGE_BITS);
     for (addr = start; addr <= end; addr += TARGET_PAGE_SIZE) {


And a non-terminating migration - not sure if this is the cause.

-- 
error compiling committee.c: too many arguments to function