Re: [PATCH v7 14/27] KVM: Allow 2048-bit register access via ioctl interface

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On Fri, Mar 29, 2019 at 01:00:39PM +0000, Dave Martin wrote:
> The Arm SVE architecture defines registers that are up to 2048 bits
> in size (with some possibility of further future expansion).
> 
> In order to avoid the need for an excessively large number of
> ioctls when saving and restoring a vcpu's registers, this patch
> adds a #define to make support for individual 2048-bit registers
> through the KVM_{GET,SET}_ONE_REG ioctl interface official.  This
> will allow each SVE register to be accessed in a single call.
> 
> There are sufficient spare bits in the register id size field for
> this change, so there is no ABI impact, providing that
> KVM_GET_REG_LIST does not enumerate any 2048-bit register unless
> userspace explicitly opts in to the relevant architecture-specific
> features.
> 
> Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
> Reviewed-by: Alex Bennée <alex.bennee@xxxxxxxxxx>
> Tested-by: zhang.lei <zhang.lei@xxxxxxxxxxxxxx>
> ---
>  include/uapi/linux/kvm.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 6d4ea4b..dc77a5a 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1145,6 +1145,7 @@ struct kvm_dirty_tlb {
>  #define KVM_REG_SIZE_U256	0x0050000000000000ULL
>  #define KVM_REG_SIZE_U512	0x0060000000000000ULL
>  #define KVM_REG_SIZE_U1024	0x0070000000000000ULL
> +#define KVM_REG_SIZE_U2048	0x0080000000000000ULL
>  
>  struct kvm_reg_list {
>  	__u64 n; /* number of regs */
> -- 
> 2.1.4
>

Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
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