From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f200.google.com (mail-pl1-f200.google.com [209.85.214.200]) by kanga.kvack.org (Postfix) with ESMTP id A2B4D6B026A for ; Thu, 1 Nov 2018 06:45:58 -0400 (EDT) Received: by mail-pl1-f200.google.com with SMTP id s23-v6so3794561plq.7 for ; Thu, 01 Nov 2018 03:45:58 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id h4-v6sor27048937plk.55.2018.11.01.03.45.57 for (Google Transport Security); Thu, 01 Nov 2018 03:45:57 -0700 (PDT) Date: Thu, 1 Nov 2018 21:45:52 +1100 From: Balbir Singh Subject: Re: [RFC PATCH v1 2/4] kvmppc: Add support for shared pages in HMM driver Message-ID: <20181101104552.GE16399@350D> References: <20181022051837.1165-1-bharata@linux.ibm.com> <20181022051837.1165-3-bharata@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181022051837.1165-3-bharata@linux.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Bharata B Rao Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, linux-mm@kvack.org, paulus@au1.ibm.com, benh@linux.ibm.com, aneesh.kumar@linux.vnet.ibm.com, jglisse@redhat.com, linuxram@us.ibm.com On Mon, Oct 22, 2018 at 10:48:35AM +0530, Bharata B Rao wrote: > A secure guest will share some of its pages with hypervisor (Eg. virtio > bounce buffers etc). Support shared pages in HMM driver. > > Signed-off-by: Bharata B Rao > --- > arch/powerpc/kvm/book3s_hv_hmm.c | 69 ++++++++++++++++++++++++++++++-- > 1 file changed, 65 insertions(+), 4 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv_hmm.c b/arch/powerpc/kvm/book3s_hv_hmm.c > index a2ee3163a312..09b8e19b7605 100644 > --- a/arch/powerpc/kvm/book3s_hv_hmm.c > +++ b/arch/powerpc/kvm/book3s_hv_hmm.c > @@ -50,6 +50,7 @@ struct kvmppc_hmm_page_pvt { > struct hlist_head *hmm_hash; > unsigned int lpid; > unsigned long gpa; > + bool skip_page_out; > }; > > struct kvmppc_hmm_migrate_args { > @@ -278,6 +279,65 @@ static unsigned long kvmppc_gpa_to_hva(struct kvm *kvm, unsigned long gpa, > return hva; > } > > +/* > + * Shares the page with HV, thus making it a normal page. > + * > + * - If the page is already secure, then provision a new page and share > + * - If the page is a normal page, share the existing page > + * > + * In the former case, uses the HMM fault handler to release the HMM page. > + */ > +static unsigned long > +kvmppc_share_page(struct kvm *kvm, unsigned long gpa, > + unsigned long addr, unsigned long page_shift) > +{ > + So this is a special flag passed via the hypercall to say this page can be skipped from page_out from secure memory? Who has the master copy of the page at this point? In which case the question is Why did we get a fault on the page which resulted in the fault migration ops being called? What category of pages are considered shared? Balbir