Re: [Xen-devel] [PATCH v8 4/6] arm/vm_event: get/set registers

[Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

On Wed, Jul 6, 2016 at 1:43 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 05.07.16 at 20:37, <tamas.lengyel@xxxxxxxxxxxx> wrote:
>> +struct vm_event_regs_arm64 {
>> +    uint64_t x0;
>> +    uint64_t x1;
>> +    uint64_t x2;
>> +    uint64_t x3;
>> +    uint64_t x4;
>> +    uint64_t x5;
>> +    uint64_t x6;
>> +    uint64_t x7;
>> +    uint64_t x8;
>> +    uint64_t x9;
>> +    uint64_t x10;
>> +    uint64_t x11;
>> +    uint64_t x12;
>> +    uint64_t x13;
>> +    uint64_t x14;
>> +    uint64_t x15;
>> +    uint64_t x16;
>> +    uint64_t x17;
>> +    uint64_t x18;
>> +    uint64_t x19;
>> +    uint64_t x20;
>> +    uint64_t x21;
>> +    uint64_t x22;
>> +    uint64_t x23;
>> +    uint64_t x24;
>> +    uint64_t x25;
>> +    uint64_t x26;
>> +    uint64_t x27;
>> +    uint64_t x28;
>> +    uint64_t x29;
>> +    uint64_t x30;
>> +    uint64_t pc;
>> +};
>
> Isn't the stack pointer a fully separate register in aarch64? Not
> making available something as essential as that seems wrong to
> me.
>

The register is available for access already, so unless there is an
actual use-case that requires it to be transmitted through vm_event I
don't see the point for transmitting it. So as I mentioned in my other
response, I'm inclined to reduce this patch to the bare essentials my
use-case requires at this point and leave the extensions up for the
future when - and if - it will be of use. Since this patch is just an
optimization, if transmitting such reduced set is not acceptable for
some reason, I'll forgo this patch entirely.

Thanks,
Tamas

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