From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:36567) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gttTd-0001Jk-IV for qemu-devel@nongnu.org; Wed, 13 Feb 2019 07:17:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gttTc-0003Rk-8n for qemu-devel@nongnu.org; Wed, 13 Feb 2019 07:17:21 -0500 Received: from mail-wr1-f67.google.com ([209.85.221.67]:34378) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gttTa-0003Ej-7g for qemu-devel@nongnu.org; Wed, 13 Feb 2019 07:17:20 -0500 Received: by mail-wr1-f67.google.com with SMTP id f14so2270024wrg.1 for ; Wed, 13 Feb 2019 04:17:08 -0800 (PST) Date: Wed, 13 Feb 2019 13:17:03 +0100 From: Stefano Garzarella Message-ID: <20190213121703.zmzpgl4fvvsfg4pf@steredhat> References: <1550022537-27565-1-git-send-email-changpeng.liu@intel.com> <20190213080143.GE26332@stefanha-x1.localdomain> <20190213083227.xkih3ckbtiromd2v@steredhat> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190213083227.xkih3ckbtiromd2v@steredhat> Subject: Re: [Qemu-devel] [PATCH v4] virtio-blk: set correct config size for the host driver List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , Changpeng Liu , mst@redhat.com Cc: qemu-devel@nongnu.org, ldoktor@redhat.com, dgilbert@redhat.com, stefanha@redhat.com, Greg Kurz On Wed, Feb 13, 2019 at 09:32:27AM +0100, Stefano Garzarella wrote: > On Wed, Feb 13, 2019 at 04:01:43PM +0800, Stefan Hajnoczi wrote: > > On Wed, Feb 13, 2019 at 09:48:57AM +0800, Changpeng Liu wrote: > > > Commit caa1ee43 "vhost-user-blk: add discard/write zeroes features > > > support" added fields to struct virtio_blk_config. This changes > > > the size of the config space and breaks migration from QEMU 3.1 > > > and older: > > > > > > qemu-system-ppc64: get_pci_config_device: Bad config data: i=0x10 read: 41 device: 1 cmask: ff wmask: 80 w1cmask:0 > > > qemu-system-ppc64: Failed to load PCIDevice:config > > > qemu-system-ppc64: Failed to load virtio-blk:virtio > > > qemu-system-ppc64: error while loading state for instance 0x0 of device 'pci@800000020000000:01.0/virtio-blk' > > > qemu-system-ppc64: load of migration failed: Invalid argument > > > > > > Since virtio-blk doesn't support the "discard" and "write zeroes" > > > features, it shouldn't even expose the associated fields in the > > > config space actually. Just include all fields up to num_queues to > > > match QEMU 3.1 and older. > > > > > > Signed-off-by: Changpeng Liu > > > --- > > > hw/block/virtio-blk.c | 13 +++++++++---- > > > 1 file changed, 9 insertions(+), 4 deletions(-) > > > > Stefano: Please rebase your DISCARD/WRITE_ZEROES series onto this and > > check that the config space is correctly sized. Machine types before > > 4.0 shouldn't have these fields so that the config space size remains > > unchanged. > > Sure! > > Since I should set a correct config size checking if new features are > enabled or not at runtime, should be better to add a variable and an array > of sizes like in virtio-net? In my series "[PATCH v4 0/6] virtio-blk: add DISCARD and WRITE_ZEROES" I'm adding the host_features field in VirtIOBlock. Then, I could add something like the following patch (proof of concept) inspired by the virtio-net approach, that would be simplest to maintain when we will add new features. What do you think? Thanks, Stefano diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 843bb2bec8..84dcc1406c 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -28,6 +28,51 @@ #include "hw/virtio/virtio-bus.h" #include "hw/virtio/virtio-access.h" +/* + * Calculate the number of bytes up to and including the given 'field' of + * 'container'. + */ +#define endof(container, field) \ + (offsetof(container, field) + sizeof_field(container, field)) + +typedef struct VirtIOFeature { + uint64_t flags; + size_t end; +} VirtIOFeature; + +static VirtIOFeature feature_sizes[] = { + {.flags = 1ULL << VIRTIO_NET_F_SIZE_MAX, + .end = endof(struct virtio_blk_config, size_max)}, + {.flags = 1ULL << VIRTIO_NET_F_SEG_MAX, + .end = endof(struct virtio_blk_config, seg_max)}, + {.flags = 1ULL << VIRTIO_NET_F_GEOMETRY, + .end = endof(struct virtio_blk_config, geometry)}, + {.flags = 1ULL << VIRTIO_NET_F_BLK_SIZE, + .end = endof(struct virtio_blk_config, blk_size)}, + {.flags = 1ULL << VIRTIO_NET_F_TOPOLOGY, + .end = endof(struct virtio_blk_config, opt_io_size)}, + {.flags = 1ULL << VIRTIO_NET_F_CONFIG_WCE, + .end = endof(struct virtio_blk_config, wce)}, + {.flags = 1ULL << VIRTIO_NET_F_MQ, + .end = endof(struct virtio_blk_config, num_queues)}, + {} +}; + +static void virtio_blk_set_config_size(VirtIOBlock *s, uint64_t host_features) +{ + int i, config_size; + + config_size = endof(struct virtio_blk_config, capacity); + + for (i = 0; feature_sizes[i].flags != 0; i++) { + if (host_features & feature_sizes[i].flags) { + config_size = MAX(feature_sizes[i].end, config_size); + } + } + + s->config_size = config_size; +} + static void virtio_blk_init_request(VirtIOBlock *s, VirtQueue *vq, VirtIOBlockReq *req) { @@ -757,7 +802,7 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config) blkcfg.alignment_offset = 0; blkcfg.wce = blk_enable_write_cache(s->blk); virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues); - memcpy(config, &blkcfg, sizeof(struct virtio_blk_config)); + memcpy(config, &blkcfg, s->config_size); } static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config) @@ -765,7 +810,7 @@ static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config) VirtIOBlock *s = VIRTIO_BLK(vdev); struct virtio_blk_config blkcfg; - memcpy(&blkcfg, config, sizeof(blkcfg)); + memcpy(&blkcfg, config, s->config_size); aio_context_acquire(blk_get_aio_context(s->blk)); blk_set_enable_write_cache(s->blk, blkcfg.wce != 0); @@ -948,8 +993,9 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp) return; } - virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, - sizeof(struct virtio_blk_config)); + virtio_blk_set_config_size(s, s->host_features); + + virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, s->config_size); s->blk = conf->conf.blk; s->rq = NULL;