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exec.c: refactor function flatview_add_to_dispatch()

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flatview_add_to_dispatch() registers page based on the condition of
*section*, which may looks like this:

    |s|PPPPPPP|s|

where s stands for subpage and P for page.

The procedure of this function could be described as:

    - register first subpage
    - register page
    - register last subpage

This means the procedure could be simplified into these three steps
instead of a loop iteration.

This patch refactors the function into three corresponding steps and
adds some comment to clarify it.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190311054252.6094-1-richardw.yang@linux.intel.com>
[Paolo: move exit before adjustment of remain.offset_within_*,
 otherwise int128_get64 fails when a region is 2^64 bytes long]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wei Yang 2019-03-11 13:42:52 +08:00 committed by Paolo Bonzini
parent e6c165f364
commit 494d199727
1 changed files with 32 additions and 18 deletions
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42
exec.c
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@ -1599,35 +1599,49 @@ static void register_multipage(FlatView *fv,
phys_page_set(d, start_addr >> TARGET_PAGE_BITS, num_pages, section_index);
}
/*
* The range in *section* may look like this:
*
* |s|PPPPPPP|s|
*
* where s stands for subpage and P for page.
*/
void flatview_add_to_dispatch(FlatView *fv, MemoryRegionSection *section)
{
MemoryRegionSection now = *section, remain = *section;
MemoryRegionSection remain = *section;
Int128 page_size = int128_make64(TARGET_PAGE_SIZE);
if (now.offset_within_address_space & ~TARGET_PAGE_MASK) {
uint64_t left = TARGET_PAGE_ALIGN(now.offset_within_address_space)
- now.offset_within_address_space;
/* register first subpage */
if (remain.offset_within_address_space & ~TARGET_PAGE_MASK) {
uint64_t left = TARGET_PAGE_ALIGN(remain.offset_within_address_space)
- remain.offset_within_address_space;
MemoryRegionSection now = remain;
now.size = int128_min(int128_make64(left), now.size);
register_subpage(fv, &now);
} else {
now.size = int128_zero();
if (int128_eq(remain.size, now.size)) {
return;
}
while (int128_ne(remain.size, now.size)) {
remain.size = int128_sub(remain.size, now.size);
remain.offset_within_address_space += int128_get64(now.size);
remain.offset_within_region += int128_get64(now.size);
now = remain;
if (int128_lt(remain.size, page_size)) {
register_subpage(fv, &now);
} else if (remain.offset_within_address_space & ~TARGET_PAGE_MASK) {
now.size = page_size;
register_subpage(fv, &now);
} else {
}
/* register whole pages */
if (int128_ge(remain.size, page_size)) {
MemoryRegionSection now = remain;
now.size = int128_and(now.size, int128_neg(page_size));
register_multipage(fv, &now);
if (int128_eq(remain.size, now.size)) {
return;
}
remain.size = int128_sub(remain.size, now.size);
remain.offset_within_address_space += int128_get64(now.size);
remain.offset_within_region += int128_get64(now.size);
}
/* register last subpage */
register_subpage(fv, &remain);
}
void qemu_flush_coalesced_mmio_buffer(void)