Re: [RFC PATCH-for-8.0 09/10] hw/virtio: Extract vhost_user_ram_slots_max() to vhost-user-target.c

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Pierrick,

On 13/12/22 00:05, Philippe Mathieu-Daudé wrote:
> The current definition of VHOST_USER_MAX_RAM_SLOTS is
> target specific. By converting this definition to a runtime
> vhost_user_ram_slots_max() helper declared in a target
> specific unit, we can have the rest of vhost-user.c target
> independent.
> 
> To avoid variable length array or using the heap to store
> arrays of vhost_user_ram_slots_max() elements, we simply
> declare an array of the biggest VHOST_USER_MAX_RAM_SLOTS,
> and each target uses up to vhost_user_ram_slots_max()
> elements of it. Ensure arrays are big enough by adding an
> assertion in vhost_user_init().
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> RFC: Should I add VHOST_USER_MAX_RAM_SLOTS to vhost-user.h
>       or create an internal header for it?
> ---
>   hw/virtio/meson.build          |  1 +
>   hw/virtio/vhost-user-target.c  | 29 +++++++++++++++++++++++++++++
>   hw/virtio/vhost-user.c         | 26 +++++---------------------
>   include/hw/virtio/vhost-user.h |  7 +++++++
>   4 files changed, 42 insertions(+), 21 deletions(-)
>   create mode 100644 hw/virtio/vhost-user-target.c
> 
> diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
> index eb7ee8ea92..bf7e35fa8a 100644
> --- a/hw/virtio/meson.build
> +++ b/hw/virtio/meson.build
> @@ -11,6 +11,7 @@ if have_vhost
>     specific_virtio_ss.add(files('vhost.c', 'vhost-backend.c', 'vhost-iova-tree.c'))
>     if have_vhost_user
>       specific_virtio_ss.add(files('vhost-user.c'))
> +    specific_virtio_ss.add(files('vhost-user-target.c'))
>     endif
>     if have_vhost_vdpa
>       specific_virtio_ss.add(files('vhost-vdpa.c', 'vhost-shadow-virtqueue.c'))
> diff --git a/hw/virtio/vhost-user-target.c b/hw/virtio/vhost-user-target.c
> new file mode 100644
> index 0000000000..6a0d0f53d0
> --- /dev/null
> +++ b/hw/virtio/vhost-user-target.c
> @@ -0,0 +1,29 @@
> +/*
> + * vhost-user target-specific helpers
> + *
> + * Copyright (c) 2013 Virtual Open Systems Sarl.
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "hw/virtio/vhost-user.h"
> +
> +#if defined(TARGET_X86) || defined(TARGET_X86_64) || \
> +    defined(TARGET_ARM) || defined(TARGET_ARM_64)
> +#include "hw/acpi/acpi.h"
> +#elif defined(TARGET_PPC) || defined(TARGET_PPC64)
> +#include "hw/ppc/spapr.h"
> +#endif
> +
> +unsigned int vhost_user_ram_slots_max(void)
> +{
> +#if defined(TARGET_X86) || defined(TARGET_X86_64) || \
> +    defined(TARGET_ARM) || defined(TARGET_ARM_64)
> +    return ACPI_MAX_RAM_SLOTS;
> +#elif defined(TARGET_PPC) || defined(TARGET_PPC64)
> +    return SPAPR_MAX_RAM_SLOTS;
> +#else
> +    return 512;

Should vhost_user_ram_slots_max be another TargetInfo field?

> +#endif
> +}
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 8f635844af..21fc176725 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -41,24 +41,7 @@
>   #define VHOST_MEMORY_BASELINE_NREGIONS    8
>   #define VHOST_USER_F_PROTOCOL_FEATURES 30
>   #define VHOST_USER_SLAVE_MAX_FDS     8
> -
> -/*
> - * Set maximum number of RAM slots supported to
> - * the maximum number supported by the target
> - * hardware plaform.
> - */
> -#if defined(TARGET_X86) || defined(TARGET_X86_64) || \
> -    defined(TARGET_ARM) || defined(TARGET_ARM_64)
> -#include "hw/acpi/acpi.h"
> -#define VHOST_USER_MAX_RAM_SLOTS ACPI_MAX_RAM_SLOTS
> -
> -#elif defined(TARGET_PPC) || defined(TARGET_PPC64)
> -#include "hw/ppc/spapr.h"
> -#define VHOST_USER_MAX_RAM_SLOTS SPAPR_MAX_RAM_SLOTS
> -
> -#else
>   #define VHOST_USER_MAX_RAM_SLOTS 512
> -#endif
>   
>   /*
>    * Maximum size of virtio device config space
> @@ -935,7 +918,7 @@ static int vhost_user_add_remove_regions(struct vhost_dev *dev,
>   
>       if (track_ramblocks) {
>           memcpy(u->postcopy_client_bases, shadow_pcb,
> -               sizeof(uint64_t) * VHOST_USER_MAX_RAM_SLOTS);
> +               sizeof(uint64_t) * vhost_user_ram_slots_max());
>           /*
>            * Now we've registered this with the postcopy code, we ack to the
>            * client, because now we're in the position to be able to deal with
> @@ -956,7 +939,7 @@ static int vhost_user_add_remove_regions(struct vhost_dev *dev,
>   err:
>       if (track_ramblocks) {
>           memcpy(u->postcopy_client_bases, shadow_pcb,
> -               sizeof(uint64_t) * VHOST_USER_MAX_RAM_SLOTS);
> +               sizeof(uint64_t) * vhost_user_ram_slots_max());
>       }
>   
>       return ret;
> @@ -1030,7 +1013,7 @@ static int vhost_user_set_mem_table_postcopy(struct vhost_dev *dev,
>           }
>   
>           memset(u->postcopy_client_bases, 0,
> -               sizeof(uint64_t) * VHOST_USER_MAX_RAM_SLOTS);
> +               sizeof(uint64_t) * vhost_user_ram_slots_max());
>   
>           /*
>            * They're in the same order as the regions that were sent
> @@ -2169,7 +2152,7 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque,
>                   return -EINVAL;
>               }
>   
> -            u->user->memory_slots = MIN(ram_slots, VHOST_USER_MAX_RAM_SLOTS);
> +            u->user->memory_slots = MIN(ram_slots, vhost_user_ram_slots_max());
>           }
>       }
>   
> @@ -2649,6 +2632,7 @@ static void vhost_user_state_destroy(gpointer data)
>   
>   bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp)
>   {
> +    assert(vhost_user_ram_slots_max() <= VHOST_USER_MAX_RAM_SLOTS);
>       if (user->chr) {
>           error_setg(errp, "Cannot initialize vhost-user state");
>           return false;
> diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
> index 191216a74f..e13584ade8 100644
> --- a/include/hw/virtio/vhost-user.h
> +++ b/include/hw/virtio/vhost-user.h
> @@ -86,4 +86,11 @@ void vhost_user_async_close(DeviceState *d,
>                               CharBackend *chardev, struct vhost_dev *vhost,
>                               vu_async_close_fn cb);
>   
> +/**
> + * vhost_user_ram_slots_max()
> + *
> + * Return: maximum number of RAM slots supported by the target hardware plaform.
> + */
> +unsigned int vhost_user_ram_slots_max(void);
> +
>   #endif