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SubjectRe: [PATCH v5 01/10] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg
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On 1/10/23 21:26, Janis Schoetterl-Glausch wrote:
> User space can use the MEM_OP ioctl to make storage key checked reads
> and writes to the guest, however, it has no way of performing atomic,
> key checked, accesses to the guest.
> Extend the MEM_OP ioctl in order to allow for this, by adding a cmpxchg
> mode. For now, support this mode for absolute accesses only.
>
> This mode can be use, for example, to set the device-state-change
> indicator and the adapter-local-summary indicator atomically.
>
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> ---
> include/uapi/linux/kvm.h | 7 +++
> arch/s390/kvm/gaccess.h | 3 ++
> arch/s390/kvm/gaccess.c | 102 +++++++++++++++++++++++++++++++++++++++
> arch/s390/kvm/kvm-s390.c | 41 +++++++++++++++-
> 4 files changed, 151 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 55155e262646..452f43c1cc34 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -583,6 +583,8 @@ struct kvm_s390_mem_op {
> struct {
> __u8 ar; /* the access register number */
> __u8 key; /* access key, ignored if flag unset */
> + __u8 pad1[6]; /* ignored */
> + __u64 old_addr; /* ignored if flag unset */

These 3 are only used for flag values >=4, no?
They aren't used for all flag values but for specific ones, right?


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