From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60770) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1chHqZ-0007XI-Ns for qemu-devel@nongnu.org; Fri, 24 Feb 2017 10:31:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1chHqV-000835-O7 for qemu-devel@nongnu.org; Fri, 24 Feb 2017 10:31:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50698) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1chHqV-00082x-G2 for qemu-devel@nongnu.org; Fri, 24 Feb 2017 10:31:47 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8557881222 for ; Fri, 24 Feb 2017 15:31:47 +0000 (UTC) References: <20170206173306.20603-1-dgilbert@redhat.com> <20170206173306.20603-10-dgilbert@redhat.com> From: Laurent Vivier Message-ID: <4c0083ac-7b1d-ace6-d8f0-dfaa1686bd3b@redhat.com> Date: Fri, 24 Feb 2017 16:31:44 +0100 MIME-Version: 1.0 In-Reply-To: <20170206173306.20603-10-dgilbert@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 09/16] postcopy: Use temporary for placing zero huge pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, quintela@redhat.com Cc: aarcange@redhat.com On 06/02/2017 18:32, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > The kernel can't do UFFDIO_ZEROPAGE for huge pages, so we have > to allocate a temporary (always zero) page and use UFFDIO_COPYPAGE > on it. > > Signed-off-by: Dr. David Alan Gilbert > Reviewed-by: Juan Quintela > --- > include/migration/migration.h | 1 + > migration/postcopy-ram.c | 23 +++++++++++++++++++++-- > 2 files changed, 22 insertions(+), 2 deletions(-) > > diff --git a/include/migration/migration.h b/include/migration/migration.h > index c9c1d5f..bd399fc 100644 > --- a/include/migration/migration.h > +++ b/include/migration/migration.h > @@ -108,6 +108,7 @@ struct MigrationIncomingState { > QEMUFile *to_src_file; > QemuMutex rp_mutex; /* We send replies from multiple threads */ > void *postcopy_tmp_page; > + void *postcopy_tmp_zero_page; > > QEMUBH *bh; > > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index a8b7fed..4c736d2 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -324,6 +324,10 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) > munmap(mis->postcopy_tmp_page, mis->largest_page_size); > mis->postcopy_tmp_page = NULL; > } > + if (mis->postcopy_tmp_zero_page) { > + munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size); > + mis->postcopy_tmp_zero_page = NULL; > + } > trace_postcopy_ram_incoming_cleanup_exit(); > return 0; > } > @@ -593,8 +597,23 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, > return -e; > } > } else { > - /* TODO: The kernel can't use UFFDIO_ZEROPAGE for hugepages */ > - assert(0); > + /* The kernel can't use UFFDIO_ZEROPAGE for hugepages */ > + if (!mis->postcopy_tmp_zero_page) { > + mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size, > + PROT_READ | PROT_WRITE, > + MAP_PRIVATE | MAP_ANONYMOUS, > + -1, 0); > + if (mis->postcopy_tmp_zero_page == MAP_FAILED) { > + int e = errno; > + mis->postcopy_tmp_zero_page = NULL; > + error_report("%s: %s mapping large zero page", > + __func__, strerror(e)); > + return -e; > + } > + memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size); > + } > + return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, > + pagesize); > } It's sad to have to allocate 1 huge page just to zero them. Are you sure the kernel doesn't support UFFDIO_ZEROPAGE for huge page. It seems __mcopy_atomic() manages HUGETLB vma (it is called by mfill_zeropage(), called by userfaultfd_zeropage())? Anyway, the code looks good: Reviewed-by: Laurent Vivier