From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E83C3E7D0AB for ; Thu, 21 Sep 2023 21:09:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231406AbjIUVJb (ORCPT ); Thu, 21 Sep 2023 17:09:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231802AbjIUVJP (ORCPT ); Thu, 21 Sep 2023 17:09:15 -0400 Received: from mail-pl1-x649.google.com (mail-pl1-x649.google.com [IPv6:2607:f8b0:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42844CDBE6 for ; Thu, 21 Sep 2023 13:37:03 -0700 (PDT) Received: by mail-pl1-x649.google.com with SMTP id d9443c01a7336-1c448ba292dso11513395ad.3 for ; Thu, 21 Sep 2023 13:37:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1695328622; x=1695933422; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=aP7hpifj13TY/cmxy/VtYAtAKQo7n6lxac2QUYqGXnE=; b=aCsMPYSruNk/9yL3kVNkQ67ftw0JWLNZ8Ei5Se2KTIg1H7jjRUX8tAcarx71wgV4rV CenTLjy5vBKKNjV9P5bNNTnh9mjsay+f6OqT/Q+zYJApi0UEV/WySiVMfXEJQREQ8zuU 7RHX7Pk/c5pUD3oTAAvaG8+elXyX1j5ckWUOXLOkxGYf7owt5uRSY4L9zDaydEsT19NZ pPaKAZiwOjyww1gX5GeGEJn3s1zBcUep+Qn3T0S0AMYZFHc/aI0vOG/EySkgNkQnBqu4 BgQPy7AlJg+zQiaNx1gFJf/SFWCfZnrnH9J3+5kTRmGIahPoQ5ZDY0A2je7Kw9p0rV1x HOdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695328622; x=1695933422; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=aP7hpifj13TY/cmxy/VtYAtAKQo7n6lxac2QUYqGXnE=; b=Ou0VWoQ67OOJFCkpWS+l5OL5C+HZe/wV1fzsyeVVUEfKc4mlW1W29SsOgawK5CUPw9 lJO1fblOJLypRU90I3EF2ZVKPN/08DA5hSC1yxWlW5fuHm1h6UAVISk+4gfkhEUXB7o9 vtaKVwuNlLI6ozGadtEm4MRGZP0tmotPuEvq8VJtJpH4KSvy1/VZpKfYeBdghuFq4MZH JEbKbKXcDVbn83C8EWLo/9NJcHCUyup/0EeLQWSzQWBUQcG3gamdMvGi2HjrdhHCKnUu F4cislTAavIl5Ca2Ls9qCOggYN/deP1m1ut/DH8rkHZPRDSVkJIUSXK93S1+HRKlQa86 6DDQ== X-Gm-Message-State: AOJu0YxB+191LXPoeMYABFkT8Di8uIeINlJQqKkb5ZUExoX7wlc7iF1P LsTiHBvn1ihYf+SdgMzpAl9ctlLCaac= X-Google-Smtp-Source: AGHT+IEWJRg13o8CQmL28cdN0w6eaHgxHhAvKYngOPLn2gpdCakJVl0UPMB+5b2YBqkaLGEngQ4iwIMDAII= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:903:1c7:b0:1b8:3c5e:2289 with SMTP id e7-20020a17090301c700b001b83c5e2289mr84379plh.2.1695328622355; Thu, 21 Sep 2023 13:37:02 -0700 (PDT) Date: Thu, 21 Sep 2023 13:37:01 -0700 In-Reply-To: Mime-Version: 1.0 References: Message-ID: Subject: Re: [RFC PATCH v2 1/6] KVM: gmem: Truncate pages on punch hole From: Sean Christopherson To: isaku.yamahata@intel.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com, Michael Roth , Paolo Bonzini , erdemaktas@google.com, Sagi Shahar , David Matlack , Kai Huang , Zhi Wang , chen.bo@intel.com, linux-coco@lists.linux.dev, Chao Peng , Ackerley Tng , Vishal Annapurve , Yuan Yao , Jarkko Sakkinen , Xu Yilun , Quentin Perret , wei.w.wang@intel.com, Fuad Tabba Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 21, 2023, isaku.yamahata@intel.com wrote: > From: Isaku Yamahata > > 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 > --- > 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 >