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Re: [libvirt] [PATCH] snapshot: ABI stability must include memory sizing



On 13.09.2011 22:27, Eric Blake wrote:
> Commit 973fcd8f introduced the ability for qemu to reject snapshot
> reversion on an ABI incompatibility; but the very example that was
> first proposed on-list[1] as a demonstration of an ABI incompatibility,
> namely that of changing the max memory allocation, was not being
> checked for, resulting in a cryptic failure when running with larger
> max mem than what the snapshot was created with:
> error: operation failed: Error -22 while loading VM state
> 
> This commit merely protects the three variables within mem that are
> referenced by qemu_command.c, rather than all 7 (the other 4 variables
> affect cgroup handling, but have no visible effect to the qemu guest).
> 
> [1] https://www.redhat.com/archives/libvir-list/2010-December/msg00331.html
> 
> * src/conf/domain_conf.c (virDomainDefCheckABIStability): Add
> memory sizing checks.
> ---
> 
> See also https://bugzilla.redhat.com/show_bug.cgi?id=735553#c5
> 
>  src/conf/domain_conf.c |   20 ++++++++++++++++++++
>  1 files changed, 20 insertions(+), 0 deletions(-)
> 
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 11755fe..996e0d5 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -8229,6 +8229,26 @@ bool virDomainDefCheckABIStability(virDomainDefPtr src,
>          goto cleanup;
>      }
> 
> +    if (src->mem.max_balloon != dst->mem.max_balloon) {
> +        virDomainReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                             _("Target domain max memory %ld does not match source %ld"),
> +                             dst->mem.max_balloon, src->mem.max_balloon);
> +        goto cleanup;
> +    }
> +    if (src->mem.cur_balloon != dst->mem.cur_balloon) {
> +        virDomainReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                             _("Target domain current memory %ld does not match source %ld"),
> +                             dst->mem.cur_balloon, src->mem.cur_balloon);
> +        goto cleanup;
> +    }
> +    if (src->mem.hugepage_backed != dst->mem.hugepage_backed) {
> +        virDomainReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                             _("Target domain huge page backing %ld does not match source %ld"),
> +                             dst->mem.hugepage_backed,
> +                             src->mem.hugepage_backed);
> +        goto cleanup;
> +    }
> +
>      if (src->vcpus != dst->vcpus) {
>          virDomainReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>                               _("Target domain vpu count %d does not match source %d"),

ACK

Michal


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