Re: [Xen-devel] [PATCH v6 2/2] xen: move TLB-flush filtering out into populate_physmap during vm creation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.09.16 at 04:31, <dongli.zhang@xxxxxxxxxx> wrote:
> This patch implemented parts of TODO left in commit id
> a902c12ee45fc9389eb8fe54eeddaf267a555c58 (More efficient TLB-flush
> filtering in alloc_heap_pages()). It moved TLB-flush filtering out into
> populate_physmap. Because of TLB-flush in alloc_heap_pages, it's very slow
> to create a guest with memory size of more than 100GB on host with 100+
> cpus.
> 
> This patch introduced a "MEMF_no_tlbflush" bit to memflags to indicate
> whether TLB-flush should be done in alloc_heap_pages or its caller
> populate_physmap.  Once this bit is set in memflags, alloc_heap_pages will
> ignore TLB-flush. To use this bit after vm is created might lead to
> security issue, that is, this would make pages accessible to the guest B,
> when guest A may still have a cached mapping to them.
> 
> Therefore, this patch also introduced a "creation_finished" field to struct
> domain to indicate whether this domain has ever got unpaused by hypervisor.
> MEMF_no_tlbflush can be set only during vm creation phase when
> creation_finished is still false before this domain gets unpaused for the
> first time.
> 
> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
with ...

> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -386,6 +386,12 @@ struct domain
>      bool_t           disable_migrate;
>      /* Is this guest being debugged by dom0? */
>      bool_t           debugger_attached;
> +    /*
> +     * Set to true at the very end of domain creation, when the domain is
> +     * unpaused for the first time by the systemcontroller.
> +     */
> +    bool creation_finished;

... blank padding added here to match the style of the surrounding
code. I'll try to remember to take care of this during commit, but I'd
appreciate if you'd look at neighboring code next time round.

Jan


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