[Xen-devel] [PATCH v3 38/41] powerpc: convert put_page() to put_user_page*()

[john.hubbard@xxxxxxxxx]

From: John Hubbard <jhubbard@xxxxxxxxxx>

For pages that were retained via get_user_pages*(), release those pages
via the new put_user_page*() routines, instead of via put_page() or
release_pages().

This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
("mm: introduce put_user_page*(), placeholder versions").

Note that this effectively changes the code's behavior in
mm_iommu_unpin(): it now ultimately calls set_page_dirty_lock(),
instead of set_page_dirty(). This is probably more accurate.

As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [1]

[1] https://lore.kernel.org/r/20190723153640.GB720@xxxxxx

Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 arch/powerpc/kvm/book3s_64_mmu_hv.c    |  4 ++--
 arch/powerpc/kvm/book3s_64_mmu_radix.c | 19 ++++++++++++++-----
 arch/powerpc/kvm/e500_mmu.c            |  3 +--
 arch/powerpc/mm/book3s64/iommu_api.c   | 11 +++++------
 4 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c 
b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 9a75f0e1933b..18646b738ce1 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -731,7 +731,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct 
kvm_vcpu *vcpu,
                 * we have to drop the reference on the correct tail
                 * page to match the get inside gup()
                 */
-               put_page(pages[0]);
+               put_user_page(pages[0]);
        }
        return ret;
 
@@ -1206,7 +1206,7 @@ void kvmppc_unpin_guest_page(struct kvm *kvm, void *va, 
unsigned long gpa,
        unsigned long gfn;
        int srcu_idx;
 
-       put_page(page);
+       put_user_page(page);
 
        if (!dirty)
                return;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c 
b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 2d415c36a61d..f53273fbfa2d 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -821,8 +821,12 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
         */
        if (!ptep) {
                local_irq_enable();
-               if (page)
-                       put_page(page);
+               if (page) {
+                       if (upgrade_write)
+                               put_user_page(page);
+                       else
+                               put_page(page);
+               }
                return RESUME_GUEST;
        }
        pte = *ptep;
@@ -870,9 +874,14 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
                *levelp = level;
 
        if (page) {
-               if (!ret && (pte_val(pte) & _PAGE_WRITE))
-                       set_page_dirty_lock(page);
-               put_page(page);
+               bool dirty = !ret && (pte_val(pte) & _PAGE_WRITE);
+               if (upgrade_write)
+                       put_user_pages_dirty_lock(&page, 1, dirty);
+               else {
+                       if (dirty)
+                               set_page_dirty_lock(page);
+                       put_page(page);
+               }
        }
 
        /* Increment number of large pages if we (successfully) inserted one */
diff --git a/arch/powerpc/kvm/e500_mmu.c b/arch/powerpc/kvm/e500_mmu.c
index 2d910b87e441..67bb8d59d4b1 100644
--- a/arch/powerpc/kvm/e500_mmu.c
+++ b/arch/powerpc/kvm/e500_mmu.c
@@ -850,8 +850,7 @@ int kvm_vcpu_ioctl_config_tlb(struct kvm_vcpu *vcpu,
  free_privs_first:
        kfree(privs[0]);
  put_pages:
-       for (i = 0; i < num_pages; i++)
-               put_page(pages[i]);
+       put_user_pages(pages, num_pages);
  free_pages:
        kfree(pages);
        return ret;
diff --git a/arch/powerpc/mm/book3s64/iommu_api.c 
b/arch/powerpc/mm/book3s64/iommu_api.c
index b056cae3388b..e126193ba295 100644
--- a/arch/powerpc/mm/book3s64/iommu_api.c
+++ b/arch/powerpc/mm/book3s64/iommu_api.c
@@ -170,9 +170,8 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, 
unsigned long ua,
        return 0;
 
 free_exit:
-       /* free the reference taken */
-       for (i = 0; i < pinned; i++)
-               put_page(mem->hpages[i]);
+       /* free the references taken */
+       put_user_pages(mem->hpages, pinned);
 
        vfree(mem->hpas);
        kfree(mem);
@@ -203,6 +202,7 @@ static void mm_iommu_unpin(struct 
mm_iommu_table_group_mem_t *mem)
 {
        long i;
        struct page *page = NULL;
+       bool dirty = false;
 
        if (!mem->hpas)
                return;
@@ -215,10 +215,9 @@ static void mm_iommu_unpin(struct 
mm_iommu_table_group_mem_t *mem)
                if (!page)
                        continue;
 
-               if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
-                       SetPageDirty(page);
+               dirty = mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY;
 
-               put_page(page);
+               put_user_pages_dirty_lock(&page, 1, dirty);
                mem->hpas[i] = 0;
        }
 }
-- 
2.22.0


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