On Thu, Sep 21, 2023, isaku.yamahata@xxxxxxxxx wrote: > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > Although kvm_gmem_punch_hole() keeps all pages in mapping on punching hole, > it's common expectation that pages are truncated. Truncate pages on > punching hole. As page contents can be encrypted, avoid zeroing partial > folio by refusing partial punch hole. > > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > --- > virt/kvm/guest_mem.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/guest_mem.c b/virt/kvm/guest_mem.c > index a819367434e9..01fb4ca861d0 100644 > --- a/virt/kvm/guest_mem.c > +++ b/virt/kvm/guest_mem.c > @@ -130,22 +130,32 @@ static void kvm_gmem_invalidate_end(struct kvm_gmem *gmem, pgoff_t start, > static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len) > { > struct list_head *gmem_list = &inode->i_mapping->private_list; > + struct address_space *mapping = inode->i_mapping; > pgoff_t start = offset >> PAGE_SHIFT; > pgoff_t end = (offset + len) >> PAGE_SHIFT; > struct kvm_gmem *gmem; > > + /* > + * punch hole may result in zeroing partial area. As pages can be > + * encrypted, prohibit zeroing partial area. > + */ > + if (offset & ~PAGE_MASK || len & ~PAGE_MASK) > + return -EINVAL; This should be unnecessary, kvm_gmem_fallocate() does if (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len)) return -EINVAL; before invoking kvm_gmem_punch_hole(). If that's not working, i.e. your test fails, then that code needs to be fixed. I'll run your test to double-check, but AFAICT this is unnecesary. > + > /* > * Bindings must stable across invalidation to ensure the start+end > * are balanced. > */ > - filemap_invalidate_lock(inode->i_mapping); > + filemap_invalidate_lock(mapping); > > list_for_each_entry(gmem, gmem_list, entry) { > kvm_gmem_invalidate_begin(gmem, start, end); > kvm_gmem_invalidate_end(gmem, start, end); > } > > - filemap_invalidate_unlock(inode->i_mapping); > + truncate_inode_pages_range(mapping, offset, offset + len - 1); The truncate needs to happen between begin() and end(), otherwise KVM can create mappings to the memory between end() and truncate(). > + > + filemap_invalidate_unlock(mapping); > > return 0; > } > -- > 2.25.1 >