Re: [Qemu-devel] [PATCH for-3.0 v2 5/5] hw/intc/arm_gicv3_common: Move gicd shift bug handling to gicv3_post_load

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> The code currently in gicv3_gicd_no_migration_shift_bug_post_load()
> that handles migration from older QEMU versions with a particular
> bug is misplaced. We need to run this after migration in all cases,
> not just the cases where the "arm_gicv3/gicd_no_migration_shift_bug"
> subsection is present, so it must go in a post_load hook for the
> top level VMSD, not for the subsection. Move it.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  hw/intc/arm_gicv3_common.c | 77 ++++++++++++++++++--------------------
>  1 file changed, 37 insertions(+), 40 deletions(-)
> 
> diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
> index 8175889f1e7..52480c3b4cf 100644
> --- a/hw/intc/arm_gicv3_common.c
> +++ b/hw/intc/arm_gicv3_common.c
> @@ -29,6 +29,41 @@
>  #include "hw/arm/linux-boot-if.h"
>  #include "sysemu/kvm.h"
>  
> +
> +static void gicv3_gicd_no_migration_shift_bug_post_load(GICv3State *cs)
> +{
> +    if (cs->gicd_no_migration_shift_bug) {
> +        return;
> +    }
> +
> +    /* Older versions of QEMU had a bug in the handling of state save/restore
> +     * to the KVM GICv3: they got the offset in the bitmap arrays wrong,
> +     * so that instead of the data for external interrupts 32 and up
> +     * starting at bit position 32 in the bitmap, it started at bit
> +     * position 64. If we're receiving data from a QEMU with that bug,
> +     * we must move the data down into the right place.
> +     */
> +    memmove(cs->group, (uint8_t *)cs->group + GIC_INTERNAL / 8,
> +            sizeof(cs->group) - GIC_INTERNAL / 8);
> +    memmove(cs->grpmod, (uint8_t *)cs->grpmod + GIC_INTERNAL / 8,
> +            sizeof(cs->grpmod) - GIC_INTERNAL / 8);
> +    memmove(cs->enabled, (uint8_t *)cs->enabled + GIC_INTERNAL / 8,
> +            sizeof(cs->enabled) - GIC_INTERNAL / 8);
> +    memmove(cs->pending, (uint8_t *)cs->pending + GIC_INTERNAL / 8,
> +            sizeof(cs->pending) - GIC_INTERNAL / 8);
> +    memmove(cs->active, (uint8_t *)cs->active + GIC_INTERNAL / 8,
> +            sizeof(cs->active) - GIC_INTERNAL / 8);
> +    memmove(cs->edge_trigger, (uint8_t *)cs->edge_trigger + GIC_INTERNAL / 8,
> +            sizeof(cs->edge_trigger) - GIC_INTERNAL / 8);
> +
> +    /*
> +     * While this new version QEMU doesn't have this kind of bug as we fix it,
> +     * so it needs to set the flag to true to indicate that and it's necessary
> +     * for next migration to work from this new version QEMU.
> +     */
> +    cs->gicd_no_migration_shift_bug = true;
> +}
> +
>  static int gicv3_pre_save(void *opaque)
>  {
>      GICv3State *s = (GICv3State *)opaque;
> @@ -46,6 +81,8 @@ static int gicv3_post_load(void *opaque, int version_id)
>      GICv3State *s = (GICv3State *)opaque;
>      ARMGICv3CommonClass *c = ARM_GICV3_COMMON_GET_CLASS(s);
>  
> +    gicv3_gicd_no_migration_shift_bug_post_load(s);
> +
>      if (c->post_load) {
>          c->post_load(s);
>      }
> @@ -161,45 +198,6 @@ static int gicv3_pre_load(void *opaque)
>      return 0;
>  }
>  
> -static int gicv3_gicd_no_migration_shift_bug_post_load(void *opaque,
> -                                                       int version_id)
> -{
> -    GICv3State *cs = opaque;
> -
> -    if (cs->gicd_no_migration_shift_bug) {
> -        return 0;
> -    }
> -
> -    /* Older versions of QEMU had a bug in the handling of state save/restore
> -     * to the KVM GICv3: they got the offset in the bitmap arrays wrong,
> -     * so that instead of the data for external interrupts 32 and up
> -     * starting at bit position 32 in the bitmap, it started at bit
> -     * position 64. If we're receiving data from a QEMU with that bug,
> -     * we must move the data down into the right place.
> -     */
> -    memmove(cs->group, (uint8_t *)cs->group + GIC_INTERNAL / 8,
> -            sizeof(cs->group) - GIC_INTERNAL / 8);
> -    memmove(cs->grpmod, (uint8_t *)cs->grpmod + GIC_INTERNAL / 8,
> -            sizeof(cs->grpmod) - GIC_INTERNAL / 8);
> -    memmove(cs->enabled, (uint8_t *)cs->enabled + GIC_INTERNAL / 8,
> -            sizeof(cs->enabled) - GIC_INTERNAL / 8);
> -    memmove(cs->pending, (uint8_t *)cs->pending + GIC_INTERNAL / 8,
> -            sizeof(cs->pending) - GIC_INTERNAL / 8);
> -    memmove(cs->active, (uint8_t *)cs->active + GIC_INTERNAL / 8,
> -            sizeof(cs->active) - GIC_INTERNAL / 8);
> -    memmove(cs->edge_trigger, (uint8_t *)cs->edge_trigger + GIC_INTERNAL / 8,
> -            sizeof(cs->edge_trigger) - GIC_INTERNAL / 8);
> -
> -    /*
> -     * While this new version QEMU doesn't have this kind of bug as we fix it,
> -     * so it needs to set the flag to true to indicate that and it's necessary
> -     * for next migration to work from this new version QEMU.
> -     */
> -    cs->gicd_no_migration_shift_bug = true;
> -
> -    return 0;
> -}
> -
>  static bool needed_always(void *opaque)
>  {
>      return true;
> @@ -210,7 +208,6 @@ const VMStateDescription vmstate_gicv3_gicd_no_migration_shift_bug = {
>      .version_id = 1,
>      .minimum_version_id = 1,
>      .needed = needed_always,
> -    .post_load = gicv3_gicd_no_migration_shift_bug_post_load,
>      .fields = (VMStateField[]) {
>          VMSTATE_BOOL(gicd_no_migration_shift_bug, GICv3State),
>          VMSTATE_END_OF_LIST()
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK