From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53588) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ePmoH-0004Jw-3J for qemu-devel@nongnu.org; Fri, 15 Dec 2017 05:01:42 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ePmoC-0006Np-78 for qemu-devel@nongnu.org; Fri, 15 Dec 2017 05:01:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41420) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ePmoB-0006MP-Uh for qemu-devel@nongnu.org; Fri, 15 Dec 2017 05:01:36 -0500 Date: Fri, 15 Dec 2017 11:01:07 +0100 From: Igor Mammedov Message-ID: <20171215110107.10e7faa4@redhat.com> In-Reply-To: <20171214152010.GA4380@work-vm> References: <20171213180807.7066-1-dgilbert@redhat.com> <20171213180807.7066-2-dgilbert@redhat.com> <20171214153028.25c12b0e@redhat.com> <20171214152010.GA4380@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4 1/6] vhost: Move log_dirty check List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, maxime.coquelin@redhat.com, mst@redhat.com, groug@kaod.org On Thu, 14 Dec 2017 15:20:10 +0000 "Dr. David Alan Gilbert" wrote: > * Igor Mammedov (imammedo@redhat.com) wrote: > > On Wed, 13 Dec 2017 18:08:02 +0000 > > "Dr. David Alan Gilbert (git)" wrote: > > > > > From: "Dr. David Alan Gilbert" > > > > > > Move the log_dirty check into vhost_section. > > > > > > Signed-off-by: Dr. David Alan Gilbert > > > --- > > > hw/virtio/trace-events | 3 +++ > > > hw/virtio/vhost.c | 20 +++++++++++++------- > > > 2 files changed, 16 insertions(+), 7 deletions(-) > > > > > > diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events > > > index 775461ae98..4a493bcd46 100644 > > > --- a/hw/virtio/trace-events > > > +++ b/hw/virtio/trace-events > > > @@ -1,5 +1,8 @@ > > > # See docs/devel/tracing.txt for syntax documentation. > > > > > > +# hw/virtio/vhost.c > > > +vhost_section(const char *name, int r) "%s:%d" > > > + > > > # hw/virtio/virtio.c > > > virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned out_num) "elem %p size %zd in_num %u out_num %u" > > > virtqueue_fill(void *vq, const void *elem, unsigned int len, unsigned int idx) "vq %p elem %p len %u idx %u" > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > > > index e4290ce93d..e923219e63 100644 > > > --- a/hw/virtio/vhost.c > > > +++ b/hw/virtio/vhost.c > > > @@ -27,6 +27,7 @@ > > > #include "hw/virtio/virtio-access.h" > > > #include "migration/blocker.h" > > > #include "sysemu/dma.h" > > > +#include "trace.h" > > > > > > /* enabled until disconnected backend stabilizes */ > > > #define _VHOST_DEBUG 1 > > > @@ -567,18 +568,12 @@ static void vhost_set_memory(MemoryListener *listener, > > > memory_listener); > > > hwaddr start_addr = section->offset_within_address_space; > > > ram_addr_t size = int128_get64(section->size); > > > - bool log_dirty = > > > - memory_region_get_dirty_log_mask(section->mr) & ~(1 << DIRTY_MEMORY_MIGRATION); > > > int s = offsetof(struct vhost_memory, regions) + > > > (dev->mem->nregions + 1) * sizeof dev->mem->regions[0]; > > > void *ram; > > > > > > dev->mem = g_realloc(dev->mem, s); > > > > > > - if (log_dirty) { > > > - add = false; > > > - } > > > - > > > assert(size); > > > > > > /* Optimize no-change case. At least cirrus_vga does this a lot at this time. */ > > > @@ -611,8 +606,19 @@ static void vhost_set_memory(MemoryListener *listener, > > > > > > static bool vhost_section(MemoryRegionSection *section) > > > { > > > - return memory_region_is_ram(section->mr) && > > > + bool result; > > > + bool log_dirty = memory_region_get_dirty_log_mask(section->mr) & > > > + ~(1 << DIRTY_MEMORY_MIGRATION); > > > + result = memory_region_is_ram(section->mr) && > > > !memory_region_is_rom(section->mr); > > > + > > > + /* Vhost doesn't handle any block which is doing dirty-tracking other > > > + * than migration; this typically fires on VGA areas. > > > + */ > > > + result &= !log_dirty; > > before patch even if log_dirty, vhost_set_memory will still proceed > > and may remove dirty section from memmap and set memory_changed = true > > > > but with this patch it will just ignore such section, > > I'm not sure it's right (it might be right with new approach add/nop > > but then this patch should go after new code in place and old one > > if gone). > > I thought about that, but then I came to the conclusion that the whole > idea is that we're supposed to be ignoring these regions - so why > should they cause any change to the behaviour of vhost at all? > Thus this way seems safer. Could it happen that, while being deleted section could become dirty at the same time? if that could happen then region_del won't process section and won't call unref on it either. one more reason to operate on tmp_mem_sections and then unconditionally unref old mem_sections at commit time at the right time (after set mem table). > > Dave > > > > + > > > + trace_vhost_section(section->mr->name, result); > > > + return result; > > > } > > > > > > static void vhost_begin(MemoryListener *listener) > > > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK