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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.

Backports commit 494d199727ba248c96326b4e1c97f86eb11a5ec7 from qemu
This commit is contained in:
Wei Yang 2019-03-11 16:49:13 -04:00 committed by Lioncash
parent 963beb216d
commit 20994eca53
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GPG Key ID: 4E3C3CC1031BA9C7
1 changed files with 32 additions and 18 deletions
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50
qemu/exec.c
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@ -1105,35 +1105,49 @@ static void register_multipage(FlatView *fv,
phys_page_set(d, start_addr >> TARGET_PAGE_BITS, num_pages, section_index); 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) 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); Int128 page_size = int128_make64(TARGET_PAGE_SIZE);
if (now.offset_within_address_space & ~TARGET_PAGE_MASK) { /* register first subpage */
uint64_t left = TARGET_PAGE_ALIGN(now.offset_within_address_space) if (remain.offset_within_address_space & ~TARGET_PAGE_MASK) {
- now.offset_within_address_space; 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); now.size = int128_min(int128_make64(left), now.size);
register_subpage(fv, &now); register_subpage(fv, &now);
} else { if (int128_eq(remain.size, now.size)) {
now.size = int128_zero(); return;
} }
while (int128_ne(remain.size, now.size)) {
remain.size = int128_sub(remain.size, now.size); remain.size = int128_sub(remain.size, now.size);
remain.offset_within_address_space += int128_get64(now.size); remain.offset_within_address_space += int128_get64(now.size);
remain.offset_within_region += 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 {
now.size = int128_and(now.size, int128_neg(page_size));
register_multipage(fv, &now);
}
} }
/* 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);
} }
#ifdef __linux__ #ifdef __linux__