linux-kernel - Re: [PATCH v10 06/26] virt: gunyah: msgq: Add hypercalls to send and receive messages

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Date:   Thu, 23 Feb 2023 18:15:10 -0600
From:   Alex Elder <alex.elder@...aro.org>
To:     Elliot Berman <quic_eberman@...cinc.com>,
        Alex Elder <elder@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v10 06/26] virt: gunyah: msgq: Add hypercalls to send and
 receive messages

On 2/14/23 3:23 PM, Elliot Berman wrote:
> Add hypercalls to send and receive messages on a Gunyah message queue.
> 
> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
> ---
>   arch/arm64/gunyah/gunyah_hypercall.c | 32 ++++++++++++++++++++++++++++
>   include/linux/gunyah.h               |  7 ++++++
>   2 files changed, 39 insertions(+)
> 
> diff --git a/arch/arm64/gunyah/gunyah_hypercall.c b/arch/arm64/gunyah/gunyah_hypercall.c
> index f30d06ee80cf..2ca9ab098ff6 100644
> --- a/arch/arm64/gunyah/gunyah_hypercall.c
> +++ b/arch/arm64/gunyah/gunyah_hypercall.c
> @@ -38,6 +38,8 @@ EXPORT_SYMBOL_GPL(arch_is_gunyah_guest);
>   						   fn)
>   
>   #define GH_HYPERCALL_HYP_IDENTIFY		GH_HYPERCALL(0x8000)
> +#define GH_HYPERCALL_MSGQ_SEND			GH_HYPERCALL(0x801B)
> +#define GH_HYPERCALL_MSGQ_RECV			GH_HYPERCALL(0x801C)
>   
>   /**
>    * gh_hypercall_hyp_identify() - Returns build information and feature flags
> @@ -57,5 +59,35 @@ 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_msgq_send(u64 capid, size_t size, uintptr_t buff, int tx_flags,
> +					bool *ready)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_hvc(GH_HYPERCALL_MSGQ_SEND, capid, size, buff, tx_flags, 0, &res);
> +
> +	if (res.a0 == GH_ERROR_OK)
> +		*ready = res.a1;
> +
> +	return res.a0;
> +}
> +EXPORT_SYMBOL_GPL(gh_hypercall_msgq_send);
> +
> +enum gh_error gh_hypercall_msgq_recv(u64 capid, uintptr_t buff, size_t size, size_t *recv_size,
> +					bool *ready)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_hvc(GH_HYPERCALL_MSGQ_RECV, capid, buff, size, 0, &res);
> +
> +	if (res.a0 == GH_ERROR_OK) {
> +		*recv_size = res.a1;

Is there any chance the 64-bit size is incompatible
with size_t?  (Too big?)

> +		*ready = res.a2;

		*ready = !!res.a2;

> +	}
> +
> +	return res.a0;
> +}
> +EXPORT_SYMBOL_GPL(gh_hypercall_msgq_recv);
> +
>   MODULE_LICENSE("GPL");
>   MODULE_DESCRIPTION("Gunyah Hypervisor Hypercalls");
> diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
> index 3fef2854c5e1..cb6df4eec5c2 100644
> --- a/include/linux/gunyah.h
> +++ b/include/linux/gunyah.h
> @@ -112,4 +112,11 @@ struct gh_hypercall_hyp_identify_resp {
>   
>   void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp *hyp_identity);
>   
> +#define GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH		BIT(0)
> +
> +enum gh_error gh_hypercall_msgq_send(u64 capid, size_t size, uintptr_t buff, int tx_flags,
> +					bool *ready);

Why uintptr_t?  Why not just pass a host pointer (void *)
and do whatever conversion is necessary inside the function?

					-Alex

> +enum gh_error gh_hypercall_msgq_recv(u64 capid, uintptr_t buff, size_t size, size_t *recv_size,
> +					bool *ready);
> +
>   #endif