Re: [Minios-devel] [UNIKRAFT PATCH v2 2/5] plat/*: Set current thread on IRQ stack

[Florian Schmidt <Florian.Schmidt@xxxxxxxxx>]

Hi Costin,

I was personally wondering whether this might be easier done by simply 
having a global variable "current_thread" or something like that (and 
then, eventually, with SMP, a per-cpu variable), because it means you 
don't have to implement platform-specific handlers for this. But on the 
other side, this is how the current setup works for normal threads, so I 
think this is fine. It can always be reconsidered at a later point.
Reviewed-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>

On 5/29/19 6:56 AM, Costin Lupu wrote:
> Current thread address is saved on the top of the current thread stack.
> This patch extends this behavior for the interrupt stack in order to
> access the current thread address from interrupt context as well.
>
> Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
> ---
>   include/uk/plat/memory.h | 6 ++++++
>   plat/kvm/memory.c        | 6 ++++++
>   plat/linuxu/memory.c     | 5 +++++
>   plat/xen/memory.c        | 7 +++++++
>   4 files changed, 24 insertions(+)
>
> diff --git a/include/uk/plat/memory.h b/include/uk/plat/memory.h
> index 1bb15685..4c4e4dc4 100644
> --- a/include/uk/plat/memory.h
> +++ b/include/uk/plat/memory.h
> @@ -158,6 +158,12 @@ int ukplat_memallocator_set(struct uk_alloc *a);
>    */
>   struct uk_alloc *ukplat_memallocator_get(void);
>   
> +/**
> + * Sets the current thread address on top of kernel stack
> + * @param thread_addr Current thread address
> + */
> +void ukplat_stack_set_current_thread(void *thread_addr);
> +
>   #ifdef __cplusplus
>   }
>   #endif
> diff --git a/plat/kvm/memory.c b/plat/kvm/memory.c
> index 7f2fb46a..e96bad2c 100644
> --- a/plat/kvm/memory.c
> +++ b/plat/kvm/memory.c
> @@ -178,3 +178,9 @@ int _ukplat_mem_mappings_init(void)
>   {
>         return 0;
>   }
> +
> +void ukplat_stack_set_current_thread(void *thread_addr)
> +{
> +       *((unsigned long *) _libkvmplat_cfg.bstack.end) =
> +               (unsigned long) thread_addr;
> +}
> diff --git a/plat/linuxu/memory.c b/plat/linuxu/memory.c
> index 35d0d95c..8bfb645d 100644
> --- a/plat/linuxu/memory.c
> +++ b/plat/linuxu/memory.c
> @@ -74,3 +74,8 @@ int _ukplat_mem_mappings_init(void)
>   {
>         return 0;
>   }
> +
> +void ukplat_stack_set_current_thread(void *thread_addr __unused)
> +{
> +       /* For now, signals use the current process stack */
> +}
> diff --git a/plat/xen/memory.c b/plat/xen/memory.c
> index cb1c3552..8f170dd3 100644
> --- a/plat/xen/memory.c
> +++ b/plat/xen/memory.c
> @@ -148,3 +148,10 @@ int _ukplat_mem_mappings_init(void)
>   #endif
>         return 0;
>   }
> +
> +void ukplat_stack_set_current_thread(void *thread_addr)
> +{
> +       /* TODO revisit for HVM */
> +       extern char irqstack[];
> +       *((unsigned long *) irqstack) = (unsigned long) thread_addr;
> +}
--
Dr. Florian Schmidt
フローリアン・シュミット
Research Scientist,
Systems and Machine Learning Group
NEC Laboratories Europe
Kurfürsten-Anlage 36, D-69115 Heidelberg
Tel.     +49 (0)6221 4342-265
Fax:     +49 (0)6221 4342-155
e-mail:  florian.schmidt@xxxxxxxxx
============================================================
Registered at Amtsgericht Mannheim, Germany, HRB728558

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