Re: [RFC PATCH v12 14/33] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory
From: Yan Zhao <hidden>
Date: 2023-09-15 06:39:42
Also in:
kvm, kvm-riscv, kvmarm, linux-arm-kernel, linux-fsdevel, linux-mips, linux-mm, linux-riscv, linux-security-module, lkml
On Wed, Sep 13, 2023 at 06:55:12PM -0700, Sean Christopherson wrote:
+static struct folio *kvm_gmem_get_folio(struct file *file, pgoff_t index)
+{
+ struct folio *folio;
+
+ /* TODO: Support huge pages. */
+ folio = filemap_grab_folio(file->f_mapping, index);
+ if (IS_ERR_OR_NULL(folio))
+ return NULL;
+
+ /*
+ * Use the up-to-date flag to track whether or not the memory has been
+ * zeroed before being handed off to the guest. There is no backing
+ * storage for the memory, so the folio will remain up-to-date until
+ * it's removed.
+ *
+ * TODO: Skip clearing pages when trusted firmware will do it when
+ * assigning memory to the guest.
+ */
+ if (!folio_test_uptodate(folio)) {
+ unsigned long nr_pages = folio_nr_pages(folio);
+ unsigned long i;
+
+ for (i = 0; i < nr_pages; i++)
+ clear_highpage(folio_page(folio, i));
+
+ folio_mark_uptodate(folio);
+ }
+
+ /*
+ * Ignore accessed, referenced, and dirty flags. The memory is
+ * unevictable and there is no storage to write back to.
+ */
+ return folio;
+}If VFIO wants to map a private page, is it required to call this function for PFN?