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

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Date:   Fri, 24 Feb 2023 13:24:00 -0800
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Alex Elder <alex.elder@...aro.org>, 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 2/23/2023 4:15 PM, Alex Elder wrote:
> 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?)

This is safe because size of messages <= 240.

> 
>> +        *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
>