From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51763) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VErFr-0003rq-8q for qemu-devel@nongnu.org; Wed, 28 Aug 2013 21:42:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VErFm-0000GX-3S for qemu-devel@nongnu.org; Wed, 28 Aug 2013 21:42:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50209) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VErFl-0000GB-SK for qemu-devel@nongnu.org; Wed, 28 Aug 2013 21:42:30 -0400 Message-ID: <1377740545.10408.145.camel@ul30vt.home> From: Alex Williamson Date: Wed, 28 Aug 2013 19:42:25 -0600 In-Reply-To: <521E9DF5.9080709@ozlabs.ru> References: <1377170965-9905-1-git-send-email-aik@ozlabs.ru> <1377170965-9905-4-git-send-email-aik@ozlabs.ru> <1377703099.10408.71.camel@ul30vt.home> <521E9DF5.9080709@ozlabs.ru> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3 3/3] vfio: Fix 128 bit handling List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Kardashevskiy Cc: Paolo Bonzini , qemu-devel@nongnu.org, Peter Maydell On Thu, 2013-08-29 at 11:03 +1000, Alexey Kardashevskiy wrote: > On 08/29/2013 01:18 AM, Alex Williamson wrote: > > On Thu, 2013-08-22 at 21:29 +1000, Alexey Kardashevskiy wrote: > >> Upcoming VFIO on SPAPR PPC64 support will initialize the IOMMU > >> memory region with UINT64_MAX (2^64 bytes) size so int128_get64() > >> will assert. > >> > >> The patch takes care of this check. The existing type1 IOMMU code > >> is not expected to map all 64 bits of RAM so the patch does not > >> touch that part. > >> > >> Signed-off-by: Alexey Kardashevskiy > >> --- > >> Changes: > >> v2: > >> * used new function int128_exts64() > >> --- > >> hw/misc/vfio.c | 11 ++++++++--- > >> 1 file changed, 8 insertions(+), 3 deletions(-) > >> > >> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c > >> index dfe3a80..3878fc7 100644 > >> --- a/hw/misc/vfio.c > >> +++ b/hw/misc/vfio.c > >> @@ -1920,6 +1920,7 @@ static void vfio_listener_region_add(MemoryListener *listener, > >> VFIOContainer *container = container_of(listener, VFIOContainer, > >> iommu_data.listener); > >> hwaddr iova, end; > >> + Int128 llend; > >> void *vaddr; > >> int ret; > >> > >> @@ -1940,13 +1941,17 @@ static void vfio_listener_region_add(MemoryListener *listener, > >> } > >> > >> iova = TARGET_PAGE_ALIGN(section->offset_within_address_space); > >> - end = (section->offset_within_address_space + int128_get64(section->size)) & > >> - TARGET_PAGE_MASK; > >> + llend = int128_make64(section->offset_within_address_space); > >> + llend = int128_add(llend, section->size); > >> + llend = int128_and(llend, int128_exts64(TARGET_PAGE_MASK)); > >> > >> - if (iova >= end) { > >> + if (int128_ge(int128_make64(iova), llend)) { > >> return; > >> } > >> > >> + end = (section->offset_within_address_space + int128_get64(section->size)) & > >> + TARGET_PAGE_MASK; > >> + > > > > I'm confused, we build an Int128 version of end above for the > > comparison, why isn't this just: > > > > end = int128_get64(llend); > > > section->size for IOMMU memory region I have on spapr-vfio is 2^64 so > int128_get64() fails. But you're leaving code that does int128_get64(section->size)... how does that not assert? This patch is not maintainable. We're seemingly calculating the same value twice with no comment as to why. A hwaddr type end should be calculated from the Int128 rather than paying attention to rollover in one place but not another. Thanks, Alex