Re: [PATCH v11 23/26] virt: gunyah: Add hypercalls for sending doorbell

[Alex Elder <elder@linaro.org>]

On 3/3/23 7:06 PM, Elliot Berman wrote:
> Gunyah doorbells allow two virtual machines to signal each other using
> interrupts. Add the hypercalls needed to assert the interrupt.
> 
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>

One minor suggestion below.	-Alex

> ---
>   arch/arm64/gunyah/gunyah_hypercall.c | 25 +++++++++++++++++++++++++
>   include/linux/gunyah.h               |  3 +++
>   2 files changed, 28 insertions(+)
> 
> diff --git a/arch/arm64/gunyah/gunyah_hypercall.c b/arch/arm64/gunyah/gunyah_hypercall.c
> index f01f5cec4d23..0f1cdb706e91 100644
> --- a/arch/arm64/gunyah/gunyah_hypercall.c
> +++ b/arch/arm64/gunyah/gunyah_hypercall.c
> @@ -41,6 +41,8 @@ EXPORT_SYMBOL_GPL(arch_is_gh_guest);
>   						   fn)
>   
>   #define GH_HYPERCALL_HYP_IDENTIFY		GH_HYPERCALL(0x8000)
> +#define GH_HYPERCALL_BELL_SEND			GH_HYPERCALL(0x8012)
> +#define GH_HYPERCALL_BELL_SET_MASK		GH_HYPERCALL(0x8015)
>   #define GH_HYPERCALL_MSGQ_SEND			GH_HYPERCALL(0x801B)
>   #define GH_HYPERCALL_MSGQ_RECV			GH_HYPERCALL(0x801C)
>   #define GH_HYPERCALL_VCPU_RUN			GH_HYPERCALL(0x8065)
> @@ -63,6 +65,29 @@ void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp *hyp_identi
>   }
>   EXPORT_SYMBOL_GPL(gh_hypercall_hyp_identify);
>   
> +enum gh_error gh_hypercall_bell_send(u64 capid, u64 new_flags, u64 *old_flags)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_hvc(GH_HYPERCALL_BELL_SEND, capid, new_flags, 0, &res);
> +
> +	if (res.a0 == GH_ERROR_OK)
> +		*old_flags = res.a1;

At least one caller doesn't care about the result.  So you could
accept a null pointer as the old_flags argument, and in that case
just don't assign it.

> +
> +	return res.a0;
> +}
> +EXPORT_SYMBOL_GPL(gh_hypercall_bell_send);
> +
> +enum gh_error gh_hypercall_bell_set_mask(u64 capid, u64 enable_mask, u64 ack_mask)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_hvc(GH_HYPERCALL_BELL_SET_MASK, capid, enable_mask, ack_mask, 0, &res);
> +
> +	return res.a0;
> +}
> +EXPORT_SYMBOL_GPL(gh_hypercall_bell_set_mask);
> +
>   enum gh_error gh_hypercall_msgq_send(u64 capid, size_t size, void *buff, int tx_flags, bool *ready)
>   {
>   	struct arm_smccc_res res;
> diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
> index 37f1e2c822ce..63395dacc1a8 100644
> --- a/include/linux/gunyah.h
> +++ b/include/linux/gunyah.h
> @@ -169,6 +169,9 @@ struct gh_hypercall_hyp_identify_resp {
>   
>   void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp *hyp_identity);
>   
> +enum gh_error gh_hypercall_bell_send(u64 capid, u64 new_flags, u64 *old_flags);
> +enum gh_error gh_hypercall_bell_set_mask(u64 capid, u64 enable_mask, u64 ack_mask);
> +
>   #define GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH		BIT(0)
>   
>   enum gh_error gh_hypercall_msgq_send(u64 capid, size_t size, void *buff, int tx_flags, bool *ready);