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Fix PMM handling of 4K frames #335

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Merged
wipawel merged 4 commits into from
Nov 24, 2023
Merged

Fix PMM handling of 4K frames #335

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91f9ef4
mm/pmm: reorganize code to increase accessibility
wipawel Nov 24, 2023
27aadad
mm/pmm: use internal API for new frames array allocation
wipawel Nov 24, 2023
1413e01
mm,pmm: map percpu, idt and frames arrays in KERNEL_MAP area
wipawel Nov 24, 2023
2997618
mm/pmm: KTF must not run out of 4k frames at any point
wipawel Nov 24, 2023
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2 changes: 1 addition & 1 deletion arch/x86/traps.c
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Original file line number Diff line number Diff line change
Expand Up @@ -130,7 +130,7 @@ void init_traps(const cpu_t *cpu) {

BUG_ON(!percpu);

percpu->idt = get_free_page(GFP_KERNEL | GFP_USER);
percpu->idt = get_free_page(GFP_KERNEL_MAP | GFP_USER);
BUG_ON(!percpu->idt);

percpu->idt_ptr.size = (sizeof(idt_entry_t) * MAX_INT) - 1;
Expand Down
2 changes: 1 addition & 1 deletion common/percpu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ percpu_t *get_percpu_page(unsigned int cpu) {
/* Per CPU page must be identity mapped,
* because GDT descriptor has 32-bit base.
*/
percpu = get_free_page(GFP_IDENT | GFP_KERNEL | GFP_USER);
percpu = get_free_page(GFP_IDENT | GFP_KERNEL_MAP | GFP_USER);
BUG_ON(!percpu);
memset(percpu, 0, PAGE_SIZE);

Expand Down
139 changes: 83 additions & 56 deletions mm/pmm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ static frames_array_t early_frames;
static list_head_t free_frames[MAX_PAGE_ORDER + 1];
static list_head_t busy_frames[MAX_PAGE_ORDER + 1];

#define MIN_NUM_4K_FRAMES 2
static size_t frames_count[MAX_PAGE_ORDER + 1];

static spinlock_t lock = SPINLOCK_INIT;
Expand All @@ -64,6 +65,30 @@ static inline void init_frame(frame_t *frame) {
frame->flags.free = true;
}

static inline frame_t *reserve_frame(frame_t *frame) {
if (!frame)
return NULL;

if (frame->refcount++ == 0) {
list_unlink(&frame->list);
list_add(&frame->list, &busy_frames[frame->order]);
}

return frame;
}

static inline bool return_frame(frame_t *frame) {
ASSERT(is_frame_used(frame));

if (--frame->refcount == 0) {
list_unlink(&frame->list);
list_add(&frame->list, &free_frames[frame->order]);
return true;
}

return false;
}

static inline void init_frames_array(frames_array_t *array) {
memset(array, 0, sizeof(*array));
array->meta.free_count = ARRAY_SIZE(array->frames);
Expand All @@ -74,15 +99,16 @@ static inline void init_frames_array(frames_array_t *array) {

static frames_array_t *new_frames_array(void) {
frames_array_t *array;
frame_t *frame;

if (!boot_flags.virt) {
frame_t *frame = get_free_frame();
if (!frame)
goto error;
frame = reserve_frame(get_first_frame(free_frames, PAGE_ORDER_4K));
if (!frame)
goto error;

if (!boot_flags.virt)
array = (frames_array_t *) mfn_to_virt_kern(frame->mfn);
}
else {
array = get_free_page(GFP_KERNEL);
array = vmap_kern_4k(mfn_to_virt_map(frame->mfn), frame->mfn, L1_PROT);
if (!array)
goto error;
}
Expand Down Expand Up @@ -383,30 +409,6 @@ void init_pmm(void) {
display_frames();
}

static inline frame_t *reserve_frame(frame_t *frame) {
if (!frame)
return NULL;

if (frame->refcount++ == 0) {
list_unlink(&frame->list);
list_add(&frame->list, &busy_frames[frame->order]);
}

return frame;
}

static inline bool return_frame(frame_t *frame) {
ASSERT(is_frame_used(frame));

if (--frame->refcount == 0) {
list_unlink(&frame->list);
list_add(&frame->list, &free_frames[frame->order]);
return true;
}

return false;
}

static frame_t *_find_mfn_frame(list_head_t *list, mfn_t mfn, unsigned int order) {
frame_t *frame;

Expand Down Expand Up @@ -509,31 +511,6 @@ static frame_t *find_larger_frame(list_head_t *list, unsigned int order) {
return NULL;
}

/* Reserves and returns the first free frame fulfilling
* the condition specified by the callback.
* This function does not split larger frames.
*/
frame_t *get_free_frames_cond(free_frames_cond_t cb) {
spin_lock(&lock);
for_each_order (order) {
frame_t *frame;

if (list_is_empty(&free_frames[order]))
continue;

list_for_each_entry (frame, &free_frames[order], list) {
if (cb(frame)) {
reserve_frame(frame);
spin_unlock(&lock);
return frame;
}
}
}
spin_unlock(&lock);

return NULL;
}

static inline void relink_frame_to_order(frame_t *frame, unsigned int new_order) {
ASSERT(new_order <= MAX_PAGE_ORDER);

Expand Down Expand Up @@ -596,14 +573,62 @@ static void merge_frames(frame_t *first) {
merge_frames(first);
}

static inline bool enough_4k_frames(void) {
frame_t *frame;
int count = 0;

list_for_each_entry (frame, &free_frames[PAGE_ORDER_4K], list) {
if (++count >= MIN_NUM_4K_FRAMES)
return true;
}

return false;
}

static void try_create_4k_frames(void) {
while (!enough_4k_frames()) {
frame_t *frame = find_larger_frame(free_frames, PAGE_ORDER_4K);
if (!frame)
panic("No more frames available to create 4K frames");
split_frame(frame);
}
}

/* Reserves and returns the first free frame fulfilling
* the condition specified by the callback.
* This function does not split larger frames.
*/
frame_t *get_free_frames_cond(free_frames_cond_t cb) {
spin_lock(&lock);
try_create_4k_frames();
for_each_order (order) {
frame_t *frame;

list_for_each_entry (frame, &free_frames[order], list) {
if (cb(frame)) {
reserve_frame(frame);
spin_unlock(&lock);
return frame;
}
}
}
spin_unlock(&lock);

return NULL;
}

frame_t *get_free_frames(unsigned int order) {
frame_t *frame;

if (order > MAX_PAGE_ORDER)
return NULL;

spin_lock(&lock);
if (order == PAGE_ORDER_4K)
try_create_4k_frames();

while (list_is_empty(&free_frames[order])) {
BUG_ON(order == PAGE_ORDER_4K);
frame = find_larger_frame(free_frames, order);
if (!frame) {
spin_unlock(&lock);
Expand Down Expand Up @@ -643,7 +668,9 @@ void map_frames_array(void) {

list_for_each_entry (array, &frames, list) {
mfn_t mfn = virt_to_mfn(array);
void *va = IS_ADDR_SPACE_VA(array, VIRT_KERNEL_BASE) ? mfn_to_virt_kern(mfn)
: mfn_to_virt_map(mfn);

BUG_ON(!vmap_kern_4k(mfn_to_virt_kern(mfn), mfn, L1_PROT));
BUG_ON(!vmap_kern_4k(va, mfn, L1_PROT));
}
}