Re: [PATCH v5 10/15] KVM: s390: add functions to (un)register GISC with GISA

[Michael Mueller]

On 19.12.18 20:17, Michael Mueller wrote:
> Add the IAM (Interruption Alert Mask) to the architecture specific
> kvm struct. This mask in the GISA is used to define for which ISC
> a GIB alert can be issued.
>
> The functions kvm_s390_gisc_register() and kvm_s390_gisc_unregister()
> are used to (un)register a GISC (guest ISC) with a virtual machine and
> its GISA.
>
> Upon successful completion, kvm_s390_gisc_register() returns the
> ISC to be used for GIB alert interruptions. A negative return code
> indicates an error during registration.
>
> Theses functions will be used by other adapter types like AP and PCI to
> request pass-through interruption support.
>
> Signed-off-by: Michael Mueller <mimu@xxxxxxxxxxxxx>
> ---
>   arch/s390/include/asm/kvm_host.h |  9 ++++++
>   arch/s390/kvm/interrupt.c        | 66 ++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 75 insertions(+)

...

> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -229,6 +229,25 @@ static inline u8 int_word_to_isc(u32 int_word)
>    */
>   #define IPM_BIT_OFFSET (offsetof(struct kvm_s390_gisa, ipm) * BITS_PER_BYTE)
>   
> +static inline int set_iam(struct kvm_s390_gisa *gisa, u8 iam)

I will rename this one here as well to gisa_set_iam()

> +{
> +	u64 word0, _word0;
> +
> +	do {
> +		word0 = READ_ONCE(gisa->u64.word[0]);
> +		/* If the GISA is in the alert list, do nothing. */
> +		if ((u64)gisa != word0 >> 32)
> +			return -EBUSY;
> +		/*
> +		 * Try to set the IAM or loop, if the IPM has changed
> +		 * or the GISA has been inserted into the alert list.
> +		 */
> +		_word0 = (word0 & ~0xffUL) | iam;
> +	} while (cmpxchg(&gisa->u64.word[0], word0, _word0) != _word0);
> +
> +	return 0;
> +}
> +