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Re: [libvirt] [PATCH] virDomainDefCheckABIStabilityFlags: Check for memoryBacking



On Thu, May 18, 2017 at 10:05:55 +0200, Michal Privoznik wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1450349
> 
> Problem is, memoryBacking is part of guest ABI. Therefore
> changing it on migration/restore from an image can lead
> qemu/guest to rejecting the image.
> 
> At the same time, move other partial checks of virDomainMemtune
> into the same function: virDomainMemtuneCheckABIStability.
> 
> Signed-off-by: Michal Privoznik <mprivozn redhat com>
> ---
>  src/conf/domain_conf.c | 101 ++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 75 insertions(+), 26 deletions(-)
> 
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 9eba70a95..89b93f4ad 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -19786,6 +19786,80 @@ virDomainTPMDefCheckABIStability(virDomainTPMDefPtr src,
>      return virDomainDeviceInfoCheckABIStability(&src->info, &dst->info);
>  }
>  
> +
> +static bool
> +virDomainMemtuneCheckABIStability(const virDomainDef *src,
> +                                  const virDomainDef *dst,
> +                                  unsigned int flags)
> +{
> +    if (virDomainDefGetMemoryInitial(src) != virDomainDefGetMemoryInitial(dst)) {
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       _("Target domain max memory %lld "
> +                         "does not match source %lld"),
> +                       virDomainDefGetMemoryInitial(dst),
> +                       virDomainDefGetMemoryInitial(src));
> +        return false;
> +    }
> +
> +    if (!(flags & VIR_DOMAIN_DEF_ABI_CHECK_SKIP_VOLATILE) &&
> +        src->mem.cur_balloon != dst->mem.cur_balloon) {
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       _("Target domain current memory %lld "
> +                         "does not match source %lld"),
> +                       dst->mem.cur_balloon,
> +                       src->mem.cur_balloon);
> +        return false;
> +    }
> +
> +    if (src->mem.max_memory != dst->mem.max_memory) {
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       _("Target maximum memory size '%llu' "
> +                         "doesn't match source '%llu'"),
> +                       dst->mem.max_memory,
> +                       src->mem.max_memory);
> +        return false;
> +    }
> +
> +    if (src->mem.memory_slots != dst->mem.memory_slots) {
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       _("Target domain memory slots "
> +                         "count '%u' doesn't match source '%u'"),
> +                       dst->mem.memory_slots,
> +                       src->mem.memory_slots);
> +        return false;
> +    }
> +
> +    if (src->mem.source != dst->mem.source) {
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       _("Target memoryBacking source '%s' doesn't "
> +                         "match source memoryBacking source'%s'"),
> +                       virDomainMemorySourceTypeToString(dst->mem.source),
> +                       virDomainMemorySourceTypeToString(src->mem.source));
> +        return false;
> +    }
AFAIK this is guest ABI only because qemu uses this to generate
hugepages rather than regular memory, not that it would be guest ABI
per se.

> +
> +    if (src->mem.access != dst->mem.access) {
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       _("Target memoryBacking access '%s' doesn't "
> +                         "match access memoryBacking access'%s'"),
> +                       virDomainMemoryAccessTypeToString(dst->mem.access),
> +                       virDomainMemoryAccessTypeToString(src->mem.access));
> +        return false;

Same here, shared access does not really transform to guest ABI.

> +    }
> +
> +    if (src->mem.allocation != dst->mem.allocation) {
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       _("Target memoryBacking allocation '%s' doesn't "
> +                         "match allocation memoryBacking allocation'%s'"),
> +                       virDomainMemoryAllocationTypeToString(dst->mem.allocation),
> +                       virDomainMemoryAllocationTypeToString(src->mem.allocation));
> +        return false;

This is definitely not guest ABI.


Note that there's a difference between guest ABI and differences in
configurations which are rejected by qemu.

I think we need a mechanism to deal with these in a different way
because it's possible that other hypervisors will have different ideas
on the compatibility of these options.

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