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Re: [PATCH v5 05/12] arm/sve: save/restore SVE context switch
- To: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Thu, 20 Apr 2023 08:33:18 +0000
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Chen <Wei.Chen@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Thu, 20 Apr 2023 08:33:54 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH v5 05/12] arm/sve: save/restore SVE context switch
Hi Luca,
> On 20 Apr 2023, at 09:58, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
>
>>>
>>> Hi Bertrand,
>>>
>>> These are the changes I’m doing to this patch to address your comment, are
>>> you ok with them?
>>>
>>> diff --git a/xen/arch/arm/arm64/sve.c b/xen/arch/arm/arm64/sve.c
>>> index f0eab18dc384..1fef466ba0aa 100644
>>> --- a/xen/arch/arm/arm64/sve.c
>>> +++ b/xen/arch/arm/arm64/sve.c
>>> @@ -91,35 +91,35 @@ int sve_context_init(struct vcpu *v)
>>> if ( !ctx )
>>> return -ENOMEM;
>>>
>>> - v->arch.vfp.sve_context = ctx;
>>> + /* Point to the end of Z0-Z31 memory, just before FFR memory */
>>> + v->arch.vfp.sve_zreg_ctx_end = ctx +
>>> + (sve_zreg_ctx_size(sve_vl_bits) / sizeof(uint64_t));
>>>
>>> return 0;
>>> }
>>>
>>> void sve_context_free(struct vcpu *v)
>>> {
>>> - XFREE(v->arch.vfp.sve_context);
>>> + unsigned int sve_vl_bits = sve_decode_vl(v->domain->arch.sve_vl);
>>> +
>>> + /* Point back to the beginning of Z0-Z31 + FFR memory */
>>> + v->arch.vfp.sve_zreg_ctx_end = v->arch.vfp.sve_zreg_ctx_end -
>>> + (sve_zreg_ctx_size(sve_vl_bits) / sizeof(uint64_t));
>>
>> Please use a local variable here instead.
>>
>> For the rest all good yes, it makes the save/restore code simpler :-)
>>
>
> I did at the beginning, but then I realised XFREE would set to NULL the local
> variable instead,
> I could open code it and call xfree on the local variable and put
> v->arch.vfp.sve_zreg_ctx_end
> to NULL afterwards, but Julien asked me to use XFREE.
>
> What is your preference here?
>
I did not realised XFREE was actually also setting it to NULL.
Then i would keep your code but use -= instead.
Cheers
Bertrand
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