[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v9] vhost: used_memslots refactoring
|
From: |
Zhoujian (jay) |
|
Subject: |
Re: [Qemu-devel] [PATCH v9] vhost: used_memslots refactoring |
|
Date: |
Tue, 20 Mar 2018 14:45:09 +0000 |
> -----Original Message-----
> From: Michael S. Tsirkin [mailto:address@hidden
> Sent: Tuesday, March 20, 2018 8:36 PM
> To: Zhoujian (jay) <address@hidden>
> Cc: address@hidden; address@hidden; Huangweidong (C)
> <address@hidden>; wangxin (U) <address@hidden>; Gonglei
> (Arei) <address@hidden>; Liuzhe (Ahriy, Euler) <address@hidden>
> Subject: Re: [PATCH v9] vhost: used_memslots refactoring
>
> On Tue, Mar 20, 2018 at 03:39:17AM +0000, Zhoujian (jay) wrote:
> >
> >
> > > -----Original Message-----
> > > From: Michael S. Tsirkin [mailto:address@hidden
> > > Sent: Tuesday, March 20, 2018 10:51 AM
> > > To: Zhoujian (jay) <address@hidden>
> > > Cc: address@hidden; address@hidden; Huangweidong (C)
> > > <address@hidden>; wangxin (U)
> > > <address@hidden>; Gonglei
> > > (Arei) <address@hidden>; Liuzhe (Ahriy, Euler)
> > > <address@hidden>
> > > Subject: Re: [PATCH v9] vhost: used_memslots refactoring
> > >
> > > On Tue, Mar 20, 2018 at 02:09:34AM +0000, Zhoujian (jay) wrote:
> > > > Hi Michael,
> > > >
> > > > > -----Original Message-----
> > > > > From: Michael S. Tsirkin [mailto:address@hidden
> > > > > Sent: Tuesday, March 20, 2018 9:34 AM
> > > > > To: Zhoujian (jay) <address@hidden>
> > > > > Cc: address@hidden; address@hidden; Huangweidong (C)
> > > > > <address@hidden>; wangxin (U)
> > > > > <address@hidden>; Gonglei
> > > > > (Arei) <address@hidden>; Liuzhe (Ahriy, Euler)
> > > > > <address@hidden>
> > > > > Subject: Re: [PATCH v9] vhost: used_memslots refactoring
> > > > >
> > > > > On Mon, Mar 05, 2018 at 05:12:49PM +0800, Jay Zhou wrote:
> > > > > > Used_memslots is shared by vhost kernel and user, it is equal
> > > > > > to
> > > > > > dev->mem->nregions, which is correct for vhost kernel, but not
> > > > > > dev->mem->for
> > > > > > vhost user, the latter one uses memory regions that have file
> > > > > > descriptor. E.g. a VM has a vhost-user NIC and 8(vhost user
> > > > > > memslot upper limit) memory slots, it will be failed to
> > > > > > hotplug a new DIMM device since vhost_has_free_slot() finds no
> > > > > > free slot left. It should be successful if only part of memory
> > > > > > slots have file descriptor, so setting used memslots for
> > > > > > vhost-user and vhost-
> > > kernel respectively.
> > > > >
> > > > >
> > > > > Below should go after ---
> > > >
> > > > Thanks for reminding.
> > > >
> > > > >
> > > > > > v7 ... v9:
> > > > > > - rebased on the master
> > > > > > v2 ... v6:
> > > > > > - delete the "used_memslots" global variable, and add it
> > > > > > for vhost-user and vhost-kernel separately
> > > > > > - refine the function, commit log
> > > > > > - used_memslots refactoring
> > > > > >
> > > > > > Signed-off-by: Igor Mammedov <address@hidden>
> > > > > > Signed-off-by: Jay Zhou <address@hidden>
> > > > > > Signed-off-by: Liuzhe <address@hidden>
> > > > >
> > > > > When built with clang this causes runtime warnings (during make
> > > > > check) about misaligned access to structures.
> > > > >
> > > > > The issue is that vhost_user_prepare_msg requests
> > > > > VhostUserMemory which compiler assumes but is then used with a
> > > > > pointer into a packed structure - where fields are not aligned.
> > > >
> > > > Sorry I missed the patch you have sent to fix the alignment, I
> > > > have replied to that thread.
> > > >
> > > > >
> > > > >
> > > > > > ---
> > > > > > hw/virtio/vhost-backend.c | 15 +++++++-
> > > > > > hw/virtio/vhost-user.c | 77 ++++++++++++++++++++++++++-
> ----
> > > ----
> > > > > ----
> > > > > > hw/virtio/vhost.c | 13 +++----
> > > > > > include/hw/virtio/vhost-backend.h | 6 ++-
> > > > > > 4 files changed, 75 insertions(+), 36 deletions(-)
> > > > > >
> > > > > > diff --git a/hw/virtio/vhost-backend.c
> > > > > > b/hw/virtio/vhost-backend.c index 7f09efa..59def69 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) { @@ -62,6 +64,11 @@
> > > > > > static int vhost_kernel_memslots_limit(struct vhost_dev *dev)
> > > > > > return limit;
> > > > > > }
> > > > > >
> > > > > > +static bool vhost_kernel_has_free_memslots(struct vhost_dev *dev)
> {
> > > > > > + return vhost_kernel_used_memslots <
> > > > > > +vhost_kernel_memslots_limit(dev); }
> > > > > > +
> > > > > > static int vhost_kernel_net_set_backend(struct vhost_dev *dev,
> > > > > > struct
> > > > > > vhost_vring_file
> > > > > > *file) { @@ -233,11 +240,16 @@ 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 const VhostOps kernel_ops = {
> > > > > > .backend_type = VHOST_BACKEND_TYPE_KERNEL,
> > > > > > .vhost_backend_init = vhost_kernel_init,
> > > > > > .vhost_backend_cleanup = vhost_kernel_cleanup,
> > > > > > - .vhost_backend_memslots_limit =
> vhost_kernel_memslots_limit,
> > > > > > + .vhost_backend_has_free_memslots =
> > > > > > + vhost_kernel_has_free_memslots,
> > > > > > .vhost_net_set_backend = vhost_kernel_net_set_backend,
> > > > > > .vhost_scsi_set_endpoint = vhost_kernel_scsi_set_endpoint,
> > > > > > .vhost_scsi_clear_endpoint =
> > > > > > vhost_kernel_scsi_clear_endpoint, @@ -264,6 +276,7 @@ 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,
> > > > > > };
> > > > > >
> > > > > > 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 41ff5cf..ef14249 100644
> > > > > > --- a/hw/virtio/vhost-user.c
> > > > > > +++ b/hw/virtio/vhost-user.c
> > > > > > @@ -163,6 +163,8 @@ static VhostUserMsg m __attribute__
> > > > > > ((unused));
> > > > > > /* The version of the protocol we support */
> > > > > > #define VHOST_USER_VERSION (0x1)
> > > > > >
> > > > > > +static bool vhost_user_free_memslots = true;
> > > > > > +
> > > > > > struct vhost_user {
> > > > > > CharBackend *chr;
> > > > > > int slave_fd;
> > > > > > @@ -330,12 +332,43 @@ 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,
> > > > > > +VhostUserMemory
> > > > > *mem,
> > > > > > + int *fds) {
> > > > > > + int i, fd;
> > > > > > +
> > > > > > + vhost_user_free_memslots = true;
> > > > > > + for (i = 0, mem->nregions = 0; i < dev->mem->nregions; ++i) {
> > > > > > + 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 (mem->nregions == VHOST_MEMORY_MAX_NREGIONS) {
> > > > > > + vhost_user_free_memslots = false;
> > > > > > + return -1;
> > > > > > + }
> > > > > > +
> > > > > > + mem->regions[mem->nregions].userspace_addr = reg-
> > > > > >userspace_addr;
> > > > > > + mem->regions[mem->nregions].memory_size = reg-
> >memory_size;
> > > > > > + mem->regions[mem->nregions].guest_phys_addr =
> > > > > > + reg-
> > > > > >guest_phys_addr;
> > > > > > + mem->regions[mem->nregions].mmap_offset = offset;
> > > > > > + fds[mem->nregions++] = fd;
> > > > > > + }
> > > > > > + }
> > > > > > +
> > > > > > + return 0;
> > > > > > +}
> > > > > > +
> > > > > > static int vhost_user_set_mem_table(struct vhost_dev *dev,
> > > > > > struct vhost_memory *mem) {
> > > > > > int fds[VHOST_MEMORY_MAX_NREGIONS];
> > > > > > - int i, fd;
> > > > > > - size_t fd_num = 0;
> > > > > > + size_t fd_num;
> > > > > > bool reply_supported =
> > > > > > virtio_has_feature(dev->protocol_features,
> > > > > >
> > > > > > VHOST_USER_PROTOCOL_F_REPLY_ACK);
> > > > > >
> > > > > > @@ -348,29 +381,12 @@ static int
> > > > > > vhost_user_set_mem_table(struct vhost_dev
> > > > > *dev,
> > > > > > msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> > > > > > }
> > > > > >
> > > > > > - for (i = 0; i < dev->mem->nregions; ++i) {
> > > > > > - 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) {
> > > > > > - error_report("Failed preparing vhost-user memory
> table
> > > > > msg");
> > > > > > - return -1;
> > > > > > - }
> > > > > > - msg.payload.memory.regions[fd_num].userspace_addr =
> reg-
> > > > > >userspace_addr;
> > > > > > - msg.payload.memory.regions[fd_num].memory_size = reg-
> > > > > >memory_size;
> > > > > > - msg.payload.memory.regions[fd_num].guest_phys_addr =
> reg-
> > > > > >guest_phys_addr;
> > > > > > - msg.payload.memory.regions[fd_num].mmap_offset =
> offset;
> > > > > > - fds[fd_num++] = fd;
> > > > > > - }
> > > > > > + if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0)
> {
> > > > > > + error_report("Failed preparing vhost-user memory table
> msg");
> > > > > > + return -1;
> > > > > > }
> > > > > >
> > > > > > - msg.payload.memory.nregions = fd_num;
> > > > > > + fd_num = msg.payload.memory.nregions;
> > > > > >
> > > > > > if (!fd_num) {
> > > > > > error_report("Failed initializing vhost-user memory map, "
> > > > > > @@ -886,9 +902,9 @@ static int vhost_user_get_vq_index(struct
> > > > > > vhost_dev
> > > > > *dev, int idx)
> > > > > > return idx;
> > > > > > }
> > > > > >
> > > > > > -static int vhost_user_memslots_limit(struct vhost_dev *dev)
> > > > > > +static bool vhost_user_has_free_memslots(struct vhost_dev
> > > > > > +*dev)
> > > > > > {
> > > > > > - return VHOST_MEMORY_MAX_NREGIONS;
> > > > > > + return vhost_user_free_memslots;
> > > > > > }
> > > > > >
> > > > > > static bool vhost_user_requires_shm_log(struct vhost_dev
> > > > > > *dev) @@
> > > > > > -1156,11 +1172,19 @@ vhost_user_crypto_close_session(struct
> > > > > > vhost_dev *dev,
> > > > > uint64_t session_id)
> > > > > > return 0;
> > > > > > }
> > > > > >
> > > > > > +static void vhost_user_set_used_memslots(struct vhost_dev *dev) {
> > > > > > + int fds[VHOST_MEMORY_MAX_NREGIONS];
> > > > > > + VhostUserMsg msg;
> > > > > > +
> > > > > > + vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> > > > >
> > > > > Oops. This is something I don't understand.
> > > > >
> > > > > Why is the message prepared here and then discarded?
> > > > >
> > > >
> > > > The purpose of vhost_user_set_used_memslots() is to set the
> > > > boolean value of vhost_user_free_memslots, which indicating
> > > > whether there're free memeslots for vhost user. Since there're
> > > > code duplicating inside
> > > > vhost_user_set_used_memslots() and vhost_user_set_mem_table(),
> > > > Igor suggested that we could create a new function to avoid duplicating.
> > > > Here, the value of VhostUserMsg is not needed by the caller
> > > > vhost_user_set_used_memslots(), so we just discarded.
> > > >
> > > > Regards,
> > > > Jay
> > >
> > >
> > > I think I misunderstood the meaning of that variable.
> > > It seems to be set when there are more slots than supported.
> >
> > Yes.
> >
> > >
> > > What vhost_user_free_memslots implies is that it is set when there
> > > are no free slots, even if existing config fits.
> > >
> > > A better name would be vhost_user_out_of_memslots maybe?
> >
> > vhost_user_free_memslots is set TRUE by default, if there are more
> > slots than supported it is set to FALSE.
> > vhost_user_out_of_memslots is another option, I think it should be set
> > FALSE by default, if there are more slots than supported it is set to TRUE.
> >
> > Since two functions vhost_has_free_slot() and the callback
> > vhost_backend_has_free_memslots() are using this variable, the name
> > vhost_user_free_memslots seems a little matching to these function
> > names.
>
> So vhost_has_free_slot is actually slightly wrong after your patch too.
It should be set to FALSE if the number of slots is equal to the limit, indeed.
Regards,
Jay
>
>
> > If you still prefer vhost_user_out_of_memslots, pls let me know.
> >
> > >
> > >
> > > And I missed the fact that it (as well as the prepare call) can
> > > actually fail when out of slots.
> > > Shouldn't it return status too?
> >
> > vhost_user_free_memslots is always set to false when prepare call
> > failed, this is what vhost_user_set_used_memslots() wants to do, so
> > e.g. when we hotplug memory DIMM devices, it will return false while
> calling vhost_has_free_slot().
> >
> > So, I think vhost_user_set_used_memslots() doesn't need to handle or
> > care about the return status of vhost_user_prepare_msg(), the return
> > value is only useful to another caller vhost_user_set_mem_table()
> >
> > Regards,
> > Jay
>
> So function names are a problem here I think. If the function has an
> important side effect it should be reflected in the name. Or we could add a
> wrapper which does the right thing.
>
> --
> MST