[RFC] iommu: Use put_pages_list

From: Matthew Wilcox (Oracle)
Date: Thu Sep 30 2021 - 12:26:39 EST

page->freelist is for the use of slab. We already have the ability
to free a list of pages in the core mm, but it requires the use of a
list_head and for the pages to be chained together through page->lru.
Switch the iommu code over to using free_pages_list().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
drivers/iommu/amd/io_pgtable.c | 99 +++++++++++++++-------------------
drivers/iommu/dma-iommu.c | 11 +---
drivers/iommu/intel/iommu.c | 89 +++++++++++-------------------
include/linux/iommu.h | 3 +-
4 files changed, 77 insertions(+), 125 deletions(-)

diff --git a/drivers/iommu/amd/io_pgtable.c b/drivers/iommu/amd/io_pgtable.c
index 182c93a43efd..8dfa6ee58b76 100644
--- a/drivers/iommu/amd/io_pgtable.c
+++ b/drivers/iommu/amd/io_pgtable.c
@@ -74,49 +74,37 @@ static u64 *first_pte_l7(u64 *pte, unsigned long *page_size,
*
****************************************************************************/

-static void free_page_list(struct page *freelist)
-{
- while (freelist != NULL) {
- unsigned long p = (unsigned long)page_address(freelist);
-
- freelist = freelist->freelist;
- free_page(p);
- }
-}
-
-static struct page *free_pt_page(unsigned long pt, struct page *freelist)
+static void free_pt_page(unsigned long pt, struct list_head *list)
{
struct page *p = virt_to_page((void *)pt);

- p->freelist = freelist;
-
- return p;
+ list_add_tail(&p->lru, list);
}

#define DEFINE_FREE_PT_FN(LVL, FN) \
-static struct page *free_pt_##LVL (unsigned long __pt, struct page *freelist) \
-{ \
- unsigned long p; \
- u64 *pt; \
- int i; \
- \
- pt = (u64 *)__pt; \
- \
- for (i = 0; i < 512; ++i) { \
- /* PTE present? */ \
- if (!IOMMU_PTE_PRESENT(pt[i])) \
- continue; \
- \
- /* Large PTE? */ \
- if (PM_PTE_LEVEL(pt[i]) == 0 || \
- PM_PTE_LEVEL(pt[i]) == 7) \
- continue; \
- \
- p = (unsigned long)IOMMU_PTE_PAGE(pt[i]); \
- freelist = FN(p, freelist); \
- } \
- \
- return free_pt_page((unsigned long)pt, freelist); \
+static void free_pt_##LVL (unsigned long __pt, struct list_head *list) \
+{ \
+ unsigned long p; \
+ u64 *pt; \
+ int i; \
+ \
+ pt = (u64 *)__pt; \
+ \
+ for (i = 0; i < 512; ++i) { \
+ /* PTE present? */ \
+ if (!IOMMU_PTE_PRESENT(pt[i])) \
+ continue; \
+ \
+ /* Large PTE? */ \
+ if (PM_PTE_LEVEL(pt[i]) == 0 || \
+ PM_PTE_LEVEL(pt[i]) == 7) \
+ continue; \
+ \
+ p = (unsigned long)IOMMU_PTE_PAGE(pt[i]); \
+ FN(p, list); \
+ } \
+ \
+ free_pt_page((unsigned long)pt, list); \
}

DEFINE_FREE_PT_FN(l2, free_pt_page)
@@ -125,36 +113,33 @@ DEFINE_FREE_PT_FN(l4, free_pt_l3)
DEFINE_FREE_PT_FN(l5, free_pt_l4)
DEFINE_FREE_PT_FN(l6, free_pt_l5)

-static struct page *free_sub_pt(unsigned long root, int mode,
- struct page *freelist)
+static void free_sub_pt(unsigned long root, int mode, struct list_head *list)
{
switch (mode) {
case PAGE_MODE_NONE:
case PAGE_MODE_7_LEVEL:
break;
case PAGE_MODE_1_LEVEL:
- freelist = free_pt_page(root, freelist);
+ free_pt_page(root, list);
break;
case PAGE_MODE_2_LEVEL:
- freelist = free_pt_l2(root, freelist);
+ free_pt_l2(root, list);
break;
case PAGE_MODE_3_LEVEL:
- freelist = free_pt_l3(root, freelist);
+ free_pt_l3(root, list);
break;
case PAGE_MODE_4_LEVEL:
- freelist = free_pt_l4(root, freelist);
+ free_pt_l4(root, list);
break;
case PAGE_MODE_5_LEVEL:
- freelist = free_pt_l5(root, freelist);
+ free_pt_l5(root, list);
break;
case PAGE_MODE_6_LEVEL:
- freelist = free_pt_l6(root, freelist);
+ free_pt_l6(root, list);
break;
default:
BUG();
}
-
- return freelist;
}

void amd_iommu_domain_set_pgtable(struct protection_domain *domain,
@@ -362,7 +347,7 @@ static u64 *fetch_pte(struct amd_io_pgtable *pgtable,
return pte;
}

-static struct page *free_clear_pte(u64 *pte, u64 pteval, struct page *freelist)
+static void free_clear_pte(u64 *pte, u64 pteval, struct list_head *list)
{
unsigned long pt;
int mode;
@@ -373,12 +358,12 @@ static struct page *free_clear_pte(u64 *pte, u64 pteval, struct page *freelist)
}

if (!IOMMU_PTE_PRESENT(pteval))
- return freelist;
+ return;

pt = (unsigned long)IOMMU_PTE_PAGE(pteval);
mode = IOMMU_PTE_MODE(pteval);

- return free_sub_pt(pt, mode, freelist);
+ free_sub_pt(pt, mode, list);
}

/*
@@ -392,7 +377,7 @@ static int iommu_v1_map_page(struct io_pgtable_ops *ops, unsigned long iova,
phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
{
struct protection_domain *dom = io_pgtable_ops_to_domain(ops);
- struct page *freelist = NULL;
+ LIST_HEAD(freelist);
bool updated = false;
u64 __pte, *pte;
int ret, i, count;
@@ -412,9 +397,9 @@ static int iommu_v1_map_page(struct io_pgtable_ops *ops, unsigned long iova,
goto out;

for (i = 0; i < count; ++i)
- freelist = free_clear_pte(&pte[i], pte[i], freelist);
+ free_clear_pte(&pte[i], pte[i], &freelist);

- if (freelist != NULL)
+ if (!list_empty(&freelist))
updated = true;

if (count > 1) {
@@ -449,7 +434,7 @@ static int iommu_v1_map_page(struct io_pgtable_ops *ops, unsigned long iova,
}

/* Everything flushed out, free pages now */
- free_page_list(freelist);
+ put_pages_list(&freelist);

return ret;
}
@@ -511,7 +496,7 @@ static void v1_free_pgtable(struct io_pgtable *iop)
{
struct amd_io_pgtable *pgtable = container_of(iop, struct amd_io_pgtable, iop);
struct protection_domain *dom;
- struct page *freelist = NULL;
+ LIST_HEAD(freelist);
unsigned long root;

if (pgtable->mode == PAGE_MODE_NONE)
@@ -530,9 +515,9 @@ static void v1_free_pgtable(struct io_pgtable *iop)
pgtable->mode > PAGE_MODE_6_LEVEL);

root = (unsigned long)pgtable->root;
- freelist = free_sub_pt(root, pgtable->mode, freelist);
+ free_sub_pt(root, pgtable->mode, &freelist);

- free_page_list(freelist);
+ put_pages_list(&freelist);
}

static struct io_pgtable *v1_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 896bea04c347..16742d9d8a1a 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -66,14 +66,7 @@ early_param("iommu.forcedac", iommu_dma_forcedac_setup);

static void iommu_dma_entry_dtor(unsigned long data)
{
- struct page *freelist = (struct page *)data;
-
- while (freelist) {
- unsigned long p = (unsigned long)page_address(freelist);
-
- freelist = freelist->freelist;
- free_page(p);
- }
+ put_pages_list((struct list_head *)data);
}

static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
@@ -481,7 +474,7 @@ static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie,
else if (gather && gather->queued)
queue_iova(iovad, iova_pfn(iovad, iova),
size >> iova_shift(iovad),
- (unsigned long)gather->freelist);
+ (unsigned long)&gather->freelist);
else
free_iova_fast(iovad, iova_pfn(iovad, iova),
size >> iova_shift(iovad));
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index d75f59ae28e6..eaaff646e1b4 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1186,35 +1186,30 @@ static void dma_pte_free_pagetable(struct dmar_domain *domain,
know the hardware page-walk will no longer touch them.
The 'pte' argument is the *parent* PTE, pointing to the page that is to
be freed. */
-static struct page *dma_pte_list_pagetables(struct dmar_domain *domain,
- int level, struct dma_pte *pte,
- struct page *freelist)
+static void dma_pte_list_pagetables(struct dmar_domain *domain,
+ int level, struct dma_pte *pte,
+ struct list_head *list)
{
struct page *pg;

pg = pfn_to_page(dma_pte_addr(pte) >> PAGE_SHIFT);
- pg->freelist = freelist;
- freelist = pg;
+ list_add_tail(&pg->lru, list);

if (level == 1)
- return freelist;
+ return;

pte = page_address(pg);
do {
if (dma_pte_present(pte) && !dma_pte_superpage(pte))
- freelist = dma_pte_list_pagetables(domain, level - 1,
- pte, freelist);
+ dma_pte_list_pagetables(domain, level - 1, pte, list);
pte++;
} while (!first_pte_in_page(pte));
-
- return freelist;
}

-static struct page *dma_pte_clear_level(struct dmar_domain *domain, int level,
- struct dma_pte *pte, unsigned long pfn,
- unsigned long start_pfn,
- unsigned long last_pfn,
- struct page *freelist)
+static void dma_pte_clear_level(struct dmar_domain *domain, int level,
+ struct dma_pte *pte, unsigned long pfn,
+ unsigned long start_pfn, unsigned long last_pfn,
+ struct list_head *list)
{
struct dma_pte *first_pte = NULL, *last_pte = NULL;

@@ -1235,7 +1230,7 @@ static struct page *dma_pte_clear_level(struct dmar_domain *domain, int level,
/* These suborbinate page tables are going away entirely. Don't
bother to clear them; we're just going to *free* them. */
if (level > 1 && !dma_pte_superpage(pte))
- freelist = dma_pte_list_pagetables(domain, level - 1, pte, freelist);
+ dma_pte_list_pagetables(domain, level - 1, pte, list);

dma_clear_pte(pte);
if (!first_pte)
@@ -1243,10 +1238,10 @@ static struct page *dma_pte_clear_level(struct dmar_domain *domain, int level,
last_pte = pte;
} else if (level > 1) {
/* Recurse down into a level that isn't *entirely* obsolete */
- freelist = dma_pte_clear_level(domain, level - 1,
- phys_to_virt(dma_pte_addr(pte)),
- level_pfn, start_pfn, last_pfn,
- freelist);
+ dma_pte_clear_level(domain, level - 1,
+ phys_to_virt(dma_pte_addr(pte)),
+ level_pfn, start_pfn, last_pfn,
+ list);
}
next:
pfn += level_size(level);
@@ -1255,47 +1250,28 @@ static struct page *dma_pte_clear_level(struct dmar_domain *domain, int level,
if (first_pte)
domain_flush_cache(domain, first_pte,
(void *)++last_pte - (void *)first_pte);
-
- return freelist;
}

/* We can't just free the pages because the IOMMU may still be walking
the page tables, and may have cached the intermediate levels. The
pages can only be freed after the IOTLB flush has been done. */
-static struct page *domain_unmap(struct dmar_domain *domain,
- unsigned long start_pfn,
- unsigned long last_pfn,
- struct page *freelist)
+static void domain_unmap(struct dmar_domain *domain, unsigned long start_pfn,
+ unsigned long last_pfn, struct list_head *list)
{
BUG_ON(!domain_pfn_supported(domain, start_pfn));
BUG_ON(!domain_pfn_supported(domain, last_pfn));
BUG_ON(start_pfn > last_pfn);

/* we don't need lock here; nobody else touches the iova range */
- freelist = dma_pte_clear_level(domain, agaw_to_level(domain->agaw),
- domain->pgd, 0, start_pfn, last_pfn,
- freelist);
+ dma_pte_clear_level(domain, agaw_to_level(domain->agaw),
+ domain->pgd, 0, start_pfn, last_pfn, list);

/* free pgd */
if (start_pfn == 0 && last_pfn == DOMAIN_MAX_PFN(domain->gaw)) {
struct page *pgd_page = virt_to_page(domain->pgd);
- pgd_page->freelist = freelist;
- freelist = pgd_page;
-
+ list_add_tail(&pgd_page->lru, list);
domain->pgd = NULL;
}
-
- return freelist;
-}
-
-static void dma_free_pagelist(struct page *freelist)
-{
- struct page *pg;
-
- while ((pg = freelist)) {
- freelist = pg->freelist;
- free_pgtable_page(page_address(pg));
- }
}

/* iommu handling */
@@ -1972,11 +1948,10 @@ static void domain_exit(struct dmar_domain *domain)
domain_remove_dev_info(domain);

if (domain->pgd) {
- struct page *freelist;
+ LIST_HEAD(pages);

- freelist = domain_unmap(domain, 0,
- DOMAIN_MAX_PFN(domain->gaw), NULL);
- dma_free_pagelist(freelist);
+ domain_unmap(domain, 0, DOMAIN_MAX_PFN(domain->gaw), &pages);
+ put_pages_list(&pages);
}

free_domain_mem(domain);
@@ -4068,19 +4043,17 @@ static int intel_iommu_memory_notifier(struct notifier_block *nb,
{
struct dmar_drhd_unit *drhd;
struct intel_iommu *iommu;
- struct page *freelist;
+ LIST_HEAD(pages);

- freelist = domain_unmap(si_domain,
- start_vpfn, last_vpfn,
- NULL);
+ domain_unmap(si_domain, start_vpfn, last_vpfn, &pages);

rcu_read_lock();
for_each_active_iommu(iommu, drhd)
iommu_flush_iotlb_psi(iommu, si_domain,
start_vpfn, mhp->nr_pages,
- !freelist, 0);
+ list_empty(&pages), 0);
rcu_read_unlock();
- dma_free_pagelist(freelist);
+ put_pages_list(&pages);
}
break;
}
@@ -5087,8 +5060,7 @@ static size_t intel_iommu_unmap(struct iommu_domain *domain,
start_pfn = iova >> VTD_PAGE_SHIFT;
last_pfn = (iova + size - 1) >> VTD_PAGE_SHIFT;

- gather->freelist = domain_unmap(dmar_domain, start_pfn,
- last_pfn, gather->freelist);
+ domain_unmap(dmar_domain, start_pfn, last_pfn, &gather->freelist);

if (dmar_domain->max_addr == iova + size)
dmar_domain->max_addr = iova;
@@ -5124,9 +5096,10 @@ static void intel_iommu_tlb_sync(struct iommu_domain *domain,

for_each_domain_iommu(iommu_id, dmar_domain)
iommu_flush_iotlb_psi(g_iommus[iommu_id], dmar_domain,
- start_pfn, nrpages, !gather->freelist, 0);
+ start_pfn, nrpages,
+ list_empty(&gather->freelist), 0);

- dma_free_pagelist(gather->freelist);
+ put_pages_list(&gather->freelist);
}

static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index d2f3435e7d17..de0c57a567c8 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -186,7 +186,7 @@ struct iommu_iotlb_gather {
unsigned long start;
unsigned long end;
size_t pgsize;
- struct page *freelist;
+ struct list_head freelist;
bool queued;
};

@@ -399,6 +399,7 @@ static inline void iommu_iotlb_gather_init(struct iommu_iotlb_gather *gather)
{
*gather = (struct iommu_iotlb_gather) {
.start = ULONG_MAX,
+ .freelist = LIST_HEAD_INIT(gather->freelist),
};
}

--
2.32.0