> -----Original Message----- > From: Igor Mammedov [mailto:imamm...@redhat.com] > Sent: Friday, December 29, 2017 7:22 PM > To: Zhoujian (jay) <jianjay.z...@huawei.com> > Cc: qemu-devel@nongnu.org; Huangweidong (C) <weidong.hu...@huawei.com>; > m...@redhat.com; wangxin (U) <wangxinxin.w...@huawei.com>; Liuzhe (Cloud > Open Labs, NFV) <gary.liu...@huawei.com>; Gonglei (Arei) > <arei.gong...@huawei.com> > Subject: Re: [Qemu-devel] [PATCH v3] vhost: add used memslot number for > vhost-user and vhost-kernel separately > > On Fri, 29 Dec 2017 10:37:40 +0000 > "Zhoujian (jay)" <jianjay.z...@huawei.com> wrote: > > > Hi Igor, > > > > > -----Original Message----- > > > From: Igor Mammedov [mailto:imamm...@redhat.com] > > > Sent: Friday, December 29, 2017 5:31 PM > > > To: Zhoujian (jay) <jianjay.z...@huawei.com> > > > Cc: qemu-devel@nongnu.org; Huangweidong (C) > > > <weidong.hu...@huawei.com>; m...@redhat.com; wangxin (U) > > > <wangxinxin.w...@huawei.com>; Liuzhe (Cloud Open Labs, NFV) > > > <gary.liu...@huawei.com>; Gonglei (Arei) <arei.gong...@huawei.com> > > > Subject: Re: [Qemu-devel] [PATCH v3] vhost: add used memslot number > > > for vhost-user and vhost-kernel separately > > > > > > On Fri, 29 Dec 2017 10:35:11 +0800 > > > Jay Zhou <jianjay.z...@huawei.com> wrote: > > > > > > > Used_memslots is equal to dev->mem->nregions now, it is true for > > > > vhost kernel, but not for vhost user, which uses the memory > > > > regions that have file descriptor. In fact, not all of the memory > > > > regions have file descriptor. > > > > It is usefully in some scenarios, e.g. used_memslots is 8, and > > > > only > > > > 5 memory slots can be used by vhost user, it is failed to hotplug > > > > a new DIMM memory because vhost_has_free_slot just returned false, > > > > however we can hotplug it safely in fact. > > > > > > > > Meanwhile, instead of asserting in vhost_user_set_mem_table(), > > > > error number is used to gracefully prevent device to start. This > > > > fixed the VM crash issue. > > > > > > below mostly style related comments, otherwise patch looks good to > > > me > > > > > > > > Suggested-by: Igor Mammedov <imamm...@redhat.com> > > > > Signed-off-by: Jay Zhou <jianjay.z...@huawei.com> > > > > Signed-off-by: Zhe Liu <gary.liu...@huawei.com> > > > > --- > > > > hw/virtio/vhost-backend.c | 14 +++++++ > > > > hw/virtio/vhost-user.c | 84 > +++++++++++++++++++++++++++++--- > > > ------- > > > > hw/virtio/vhost.c | 16 ++++---- > > > > include/hw/virtio/vhost-backend.h | 4 ++ > > > > 4 files changed, 91 insertions(+), 27 deletions(-) > > > > > > > > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c > > > > index 7f09efa..866718c 100644 > > > > --- a/hw/virtio/vhost-backend.c > > > > +++ b/hw/virtio/vhost-backend.c > > > > @@ -15,6 +15,8 @@ > > > > #include "hw/virtio/vhost-backend.h" > > > > #include "qemu/error-report.h" > > > > > > > > +static unsigned int vhost_kernel_used_memslots; > > > > + > > > > static int vhost_kernel_call(struct vhost_dev *dev, unsigned long > > > > int > > > request, > > > > void *arg) { @@ -233,6 +235,16 @@ > > > > static void vhost_kernel_set_iotlb_callback(struct vhost_dev *dev, > > > > qemu_set_fd_handler((uintptr_t)dev->opaque, NULL, NULL, > > > > NULL); } > > > > > > > > +static void vhost_kernel_set_used_memslots(struct vhost_dev *dev) { > > > > + vhost_kernel_used_memslots = dev->mem->nregions; } > > > > + > > > > +static unsigned int vhost_kernel_get_used_memslots(void) > > > > +{ > > > > + return vhost_kernel_used_memslots; } > > > > + > > > > static const VhostOps kernel_ops = { > > > > .backend_type = VHOST_BACKEND_TYPE_KERNEL, > > > > .vhost_backend_init = vhost_kernel_init, @@ -264,6 +276,8 > > > > @@ static const VhostOps kernel_ops = { #endif /* > CONFIG_VHOST_VSOCK */ > > > > .vhost_set_iotlb_callback = vhost_kernel_set_iotlb_callback, > > > > .vhost_send_device_iotlb_msg = > > > > vhost_kernel_send_device_iotlb_msg, > > > > + .vhost_set_used_memslots = vhost_kernel_set_used_memslots, > > > > + .vhost_get_used_memslots = > > > > + vhost_kernel_get_used_memslots, > > > > }; > > > > > > > > int vhost_set_backend_type(struct vhost_dev *dev, > > > > VhostBackendType > > > > backend_type) diff --git a/hw/virtio/vhost-user.c > > > > b/hw/virtio/vhost-user.c index 093675e..0f913be 100644 > > > > --- a/hw/virtio/vhost-user.c > > > > +++ b/hw/virtio/vhost-user.c > > > > @@ -122,6 +122,8 @@ static VhostUserMsg m __attribute__ > > > > ((unused)); > > > > /* The version of the protocol we support */ > > > > #define VHOST_USER_VERSION (0x1) > > > > > > > > +static unsigned int vhost_user_used_memslots; > > > > + > > > > struct vhost_user { > > > > CharBackend *chr; > > > > int slave_fd; > > > > @@ -289,12 +291,53 @@ static int vhost_user_set_log_base(struct > > > vhost_dev *dev, uint64_t base, > > > > return 0; > > > > } > > > > > > > > +static int vhost_user_prepare_msg(struct vhost_dev *dev, > > > > +VhostUserMsg > > > *msg, > > > > + int *fds) { > > > > + int r = 0; > > > > + int i, fd; > > > > + size_t fd_num = 0; > > > fd_num is redundant > > > you can use msg->payload.memory.nregions as a counter > > > > If using msg->payload.memory.nregions as a counter, referencing the > > member of msg->payload.memory.regions will be like this: > > > > msg->payload.memory.regions[msg- > >payload.memory.nregions].userspace_addr = ... > > msg->payload.memory.regions[msg->payload.memory.nregions].memory_size > = ... > > > > which will make the line more longer... > > > > > > > > > + > > > > + for (i = 0; i < dev->mem->nregions; ++i) { > > > for (i = 0, msg->payload.memory.nregions = 0; ... > > > > > > > + struct vhost_memory_region *reg = dev->mem->regions + i; > > > > + ram_addr_t offset; > > > > + MemoryRegion *mr; > > > > + > > > > + assert((uintptr_t)reg->userspace_addr == reg- > >userspace_addr); > > > > + mr = memory_region_from_host((void *)(uintptr_t)reg- > > > >userspace_addr, > > > > + &offset); > > > > + fd = memory_region_get_fd(mr); > > > > + if (fd > 0) { > > > > + if (fd_num < VHOST_MEMORY_MAX_NREGIONS) { > > > instead of shifting below block to the right, I'd write it like this: > > > > Without this patch, the number of characters for these two lines > > > > msg.payload.memory.regions[fd_num].userspace_addr = reg- > >userspace_addr; > > msg.payload.memory.regions[fd_num].guest_phys_addr = > > reg->guest_phys_addr; > > > > are more than 80 already... > > > > > > > > if (msg->payload.memory.nregions == > > > VHOST_MEMORY_MAX_NREGIONS) { > > > return -1; > > > } > > > > msg->payload.memory.nregions as a counter for vhost-user setting mem > > msg->table, > > while fd_num as a counter for vhost_user_used_memslots, IIUC they can > > not be merged into one counter. > > > > If return -1 when > > msg->payload.memory.nregions == VHOST_MEMORY_MAX_NREGIONS, the > > vhost_user_used_memslots maybe not assigned correctly. fd_num should > > be added by one if fd > 0 regardless of whether > > msg->payload.memory.nregions equals to or larger than > VHOST_MEMORY_MAX_NREGIONS. > > why do you need to continue counting beyond VHOST_MEMORY_MAX_NREGIONS? >
I think they're two choices (1) stop continue counting beyond VHOST_MEMORY_MAX_NREGIONS, then vhost_user_used_memslots will never larger than 8 (2) continue counting beyond VHOST_MEMORY_MAX_NREGIONS, then "hdev->vhost_ops->vhost_get_used_memslots() > hdev->vhost_ops->vhost_backend_memslots_limit(hdev)" will have a chance to be true to fail backend intialization early, which keeps commit aebf81680b does which one do you prefer? Regards, Jay