linux-kernel - Re: [PATCH v10 03/26] gunyah: Common types and error codes for Gunyah hypercalls

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Date:   Wed, 1 Mar 2023 17:40:26 -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>
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>,
        Catalin Marinas <catalin.marinas@....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 03/26] gunyah: Common types and error codes for Gunyah
 hypercalls



On 2/23/2023 1:58 PM, Alex Elder wrote:
> On 2/14/23 3:12 PM, Elliot Berman wrote:
>> Add architecture-independent standard error codes, types, and macros for
>> Gunyah hypercalls.
>>
>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
>> ---
>>   include/linux/gunyah.h | 82 ++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 82 insertions(+)
>>   create mode 100644 include/linux/gunyah.h
>>
>> diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
>> new file mode 100644
>> index 000000000000..59ef4c735ae8
>> --- /dev/null
>> +++ b/include/linux/gunyah.h
>> @@ -0,0 +1,82 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All 
>> rights reserved.
>> + */
>> +
>> +#ifndef _LINUX_GUNYAH_H
>> +#define _LINUX_GUNYAH_H
>> +
>> +#include <linux/errno.h>
>> +#include <linux/limits.h>
>> +
>> +/******************************************************************************/
>> +/* Common arch-independent definitions for Gunyah 
>> hypercalls                  */
>> +#define GH_CAPID_INVAL    U64_MAX
>> +#define GH_VMID_ROOT_VM    0xff
>> +
>> +enum gh_error {
>> +    GH_ERROR_OK            = 0,
>> +    GH_ERROR_UNIMPLEMENTED        = -1,
>> +    GH_ERROR_RETRY            = -2,
> 
> Do you expect this type to have a particular size?
> Since you specify negative values, it matters, and
> it's possible that this forces it to be a 4-byte value
> (though I'm not sure what the rules are).  In other
> words, UNIMPLEMENTED could conceivably have value 0xff
> or 0xffffffff.  I'm not even sure you can tell whether
> an enum is interpreted as signed or unsigned.

I'm not a C expert, but my understanding is that enums are signed. 
Gunyah will be returning a signed 64-bit register, however there's no 
intention to go beyond 32 bits of error codes since we want to work on 
32-bit architectures.

> 
> It's not usually a good thing to do, but this *could*
> be a case where you do a typedef to represent this as
> a signed value of a certain bit width.  (But don't do
> that unless someone else says that's worth doing.)
> 
>                      -Alex
> 
>> +
>> +    GH_ERROR_ARG_INVAL        = 1,
>> +    GH_ERROR_ARG_SIZE        = 2,
>> +    GH_ERROR_ARG_ALIGN        = 3,
>> +
>> +    GH_ERROR_NOMEM            = 10,
>> +
>> +    GH_ERROR_ADDR_OVFL        = 20,
>> +    GH_ERROR_ADDR_UNFL        = 21,
>> +    GH_ERROR_ADDR_INVAL        = 22,
>> +
>> +    GH_ERROR_DENIED            = 30,
>> +    GH_ERROR_BUSY            = 31,
>> +    GH_ERROR_IDLE            = 32,
>> +
>> +    GH_ERROR_IRQ_BOUND        = 40,
>> +    GH_ERROR_IRQ_UNBOUND        = 41,
>> +
>> +    GH_ERROR_CSPACE_CAP_NULL    = 50,
>> +    GH_ERROR_CSPACE_CAP_REVOKED    = 51,
>> +    GH_ERROR_CSPACE_WRONG_OBJ_TYPE    = 52,
>> +    GH_ERROR_CSPACE_INSUF_RIGHTS    = 53,
>> +    GH_ERROR_CSPACE_FULL        = 54,
>> +
>> +    GH_ERROR_MSGQUEUE_EMPTY        = 60,
>> +    GH_ERROR_MSGQUEUE_FULL        = 61,
>> +};
>> +
>> +/**
>> + * gh_remap_error() - Remap Gunyah hypervisor errors into a Linux 
>> error code
>> + * @gh_error: Gunyah hypercall return value
>> + */
>> +static inline int gh_remap_error(enum gh_error gh_error)
>> +{
>> +    switch (gh_error) {
>> +    case GH_ERROR_OK:
>> +        return 0;
>> +    case GH_ERROR_NOMEM:
>> +        return -ENOMEM;
>> +    case GH_ERROR_DENIED:
>> +    case GH_ERROR_CSPACE_CAP_NULL:
>> +    case GH_ERROR_CSPACE_CAP_REVOKED:
>> +    case GH_ERROR_CSPACE_WRONG_OBJ_TYPE:
>> +    case GH_ERROR_CSPACE_INSUF_RIGHTS:
>> +    case GH_ERROR_CSPACE_FULL:
>> +        return -EACCES;
>> +    case GH_ERROR_BUSY:
>> +    case GH_ERROR_IDLE:
>> +    case GH_ERROR_IRQ_BOUND:
>> +    case GH_ERROR_IRQ_UNBOUND:
>> +    case GH_ERROR_MSGQUEUE_FULL:
>> +    case GH_ERROR_MSGQUEUE_EMPTY:
> 
> Is an empty message queue really busy?
> 

Changed to -EIO.

>> +        return -EBUSY;
>> +    case GH_ERROR_UNIMPLEMENTED:
>> +    case GH_ERROR_RETRY:
>> +        return -EOPNOTSUPP;
>> +    default:
>> +        return -EINVAL;
>> +    }
>> +}
>> +
>> +#endif
>