From 8633a6ea90f85aa86f251c6295888ac211f92a2a Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Fri, 20 Nov 2015 10:44:34 +0100 Subject: [PATCH 1/9] virtio: introduce virtio_map Message-id: <1448016282-257478-2-git-send-email-imammedo@redhat.com> Patchwork-id: 68406 O-Subject: [RHEV-7.2.z qemu-kvm-rhev PATCH 1/9] virtio: introduce virtio_map Bugzilla: 1288096 RH-Acked-by: Andrew Jones RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Michael S. Tsirkin From: Michael S. Tsirkin virtio_map_sg currently fails if one of the entries it's mapping is contigious in GPA but not HVA address space. Introduce virtio_map which handles this by splitting sg entries. This new API generally turns out to be a good idea since it's harder to misuse: at least in one case the existing one was used incorrectly. This will still fail if there's no space left in the sg, but luckily max queue size in use is currently 256, while max sg size is 1024, so we should be OK even is all entries happen to cross a single DIMM boundary. Won't work well with very small DIMM sizes, unfortunately: e.g. this will fail with 4K DIMMs where a single request might span a large number of DIMMs. Let's hope these are uncommon - at least we are not breaking things. Note: virtio-scsi calls virtio_map_sg on data loaded from network, and validates input, asserting on failure. Copy the validating code here - it will be dropped from virtio-scsi in a follow-up patch. Reported-by: Igor Mammedov Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefan Hajnoczi Reviewed-by: Igor Mammedov (cherry picked from commit 8059feee004111534c4c0652e2f0715e9b4e0754) Signed-off-by: Miroslav Rezanina --- hw/virtio/virtio.c | 56 ++++++++++++++++++++++++++++++++++++++-------- include/hw/virtio/virtio.h | 1 + 2 files changed, 48 insertions(+), 9 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 0832db9..3fe6a8b 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -434,28 +434,66 @@ int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes, return in_bytes <= in_total && out_bytes <= out_total; } -void virtqueue_map_sg(struct iovec *sg, hwaddr *addr, - size_t num_sg, int is_write) +static void virtqueue_map_iovec(struct iovec *sg, hwaddr *addr, + unsigned int *num_sg, unsigned int max_size, + int is_write) { unsigned int i; hwaddr len; - if (num_sg > VIRTQUEUE_MAX_SIZE) { - error_report("virtio: map attempt out of bounds: %zd > %d", - num_sg, VIRTQUEUE_MAX_SIZE); - exit(1); - } + /* Note: this function MUST validate input, some callers + * are passing in num_sg values received over the network. + */ + /* TODO: teach all callers that this can fail, and return failure instead + * of asserting here. + * When we do, we might be able to re-enable NDEBUG below. + */ +#ifdef NDEBUG +#error building with NDEBUG is not supported +#endif + assert(*num_sg <= max_size); - for (i = 0; i < num_sg; i++) { + for (i = 0; i < *num_sg; i++) { len = sg[i].iov_len; sg[i].iov_base = cpu_physical_memory_map(addr[i], &len, is_write); - if (sg[i].iov_base == NULL || len != sg[i].iov_len) { + if (!sg[i].iov_base) { error_report("virtio: error trying to map MMIO memory"); exit(1); } + if (len == sg[i].iov_len) { + continue; + } + if (*num_sg >= max_size) { + error_report("virtio: memory split makes iovec too large"); + exit(1); + } + memmove(sg + i + 1, sg + i, sizeof(*sg) * (*num_sg - i)); + memmove(addr + i + 1, addr + i, sizeof(*addr) * (*num_sg - i)); + assert(len < sg[i + 1].iov_len); + sg[i].iov_len = len; + addr[i + 1] += len; + sg[i + 1].iov_len -= len; + ++*num_sg; } } +/* Deprecated: don't use in new code */ +void virtqueue_map_sg(struct iovec *sg, hwaddr *addr, + size_t num_sg, int is_write) +{ + virtqueue_map_iovec(sg, addr, &num_sg, num_sg, is_write); +} + +void virtqueue_map(VirtQueueElement *elem) +{ + virtqueue_map_iovec(elem->in_sg, elem->in_addr, &elem->in_num, + MIN(ARRAY_SIZE(elem->in_sg), ARRAY_SIZE(elem->in_addr)), + 1); + virtqueue_map_iovec(elem->out_sg, elem->out_addr, &elem->out_num, + MIN(ARRAY_SIZE(elem->out_sg), ARRAY_SIZE(elem->out_addr)), + 0); +} + int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem) { unsigned int i, head, max; diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index d60ca9d..f5c5086 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -151,6 +151,7 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem, void virtqueue_map_sg(struct iovec *sg, hwaddr *addr, size_t num_sg, int is_write); +void virtqueue_map(VirtQueueElement *elem); int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem); int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes, unsigned int out_bytes); -- 1.8.3.1