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Kernel: Allow specifying a physical alignment when allocating

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Some drivers may require allocating contiguous physical pages with
a specific alignment for the physical address.
This commit is contained in:
Tom 2020-12-05 22:49:24 -07:00 • committed by Andreas Kling
parent d5472426ec
commit affb4ef01b
6 changed files with 29 additions and 23 deletions
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20
Kernel/VM/PhysicalRegion.cpp
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@ -65,7 +65,7 @@ unsigned PhysicalRegion::finalize_capacity()
return size();
}
NonnullRefPtrVector<PhysicalPage> PhysicalRegion::take_contiguous_free_pages(size_t count, bool supervisor)
NonnullRefPtrVector<PhysicalPage> PhysicalRegion::take_contiguous_free_pages(size_t count, bool supervisor, size_t physical_alignment)
{
ASSERT(m_pages);
ASSERT(m_used != m_pages);
@ -73,18 +73,19 @@ NonnullRefPtrVector<PhysicalPage> PhysicalRegion::take_contiguous_free_pages(siz
NonnullRefPtrVector<PhysicalPage> physical_pages;
physical_pages.ensure_capacity(count);
auto first_contiguous_page = find_contiguous_free_pages(count);
auto first_contiguous_page = find_contiguous_free_pages(count, physical_alignment);
for (size_t index = 0; index < count; index++)
physical_pages.append(PhysicalPage::create(m_lower.offset(PAGE_SIZE * (index + first_contiguous_page)), supervisor));
return physical_pages;
}
unsigned PhysicalRegion::find_contiguous_free_pages(size_t count)
unsigned PhysicalRegion::find_contiguous_free_pages(size_t count, size_t physical_alignment)
{
ASSERT(count != 0);
ASSERT(physical_alignment % PAGE_SIZE == 0);
// search from the last page we allocated
auto range = find_and_allocate_contiguous_range(count);
auto range = find_and_allocate_contiguous_range(count, physical_alignment / PAGE_SIZE);
ASSERT(range.has_value());
return range.value();
}
@ -118,16 +119,21 @@ Optional<unsigned> PhysicalRegion::find_one_free_page()
return page_index;
}
Optional<unsigned> PhysicalRegion::find_and_allocate_contiguous_range(size_t count)
Optional<unsigned> PhysicalRegion::find_and_allocate_contiguous_range(size_t count, unsigned alignment)
{
ASSERT(count != 0);
size_t found_pages_count = 0;
auto first_index = m_bitmap.find_longest_range_of_unset_bits(count, found_pages_count);
// TODO: Improve how we deal with alignment != 1
auto first_index = m_bitmap.find_longest_range_of_unset_bits(count + alignment - 1, found_pages_count);
if (!first_index.has_value())
return {};
auto page = first_index.value();
if (count == found_pages_count) {
if (alignment != 1) {
auto lower_page = m_lower.get() / PAGE_SIZE;
page = ((lower_page + page + alignment - 1) & ~(alignment - 1)) - lower_page;
}
if (found_pages_count >= count) {
m_bitmap.set_range<true>(page, count);
m_used += count;
m_free_hint = first_index.value() + count + 1; // Just a guess