From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chas Williams <3chas3@gmail.com>
Subject: Re: [PATCH v3] bus/pci: forbid VA as IOVA mode if IOMMU
 address width too small
Date: Fri, 12 Jan 2018 17:46:25 -0500
Message-ID: <CAG2-GknMwMoKqA2y4asyUT4eUkzfsDfL1dCfOOasreTOFPeYHg@mail.gmail.com>
References: <20180112102220.20061-1-maxime.coquelin@redhat.com>
 <89c16dd0-3938-f9ae-cc9f-189388abc0a9@intel.com>
 <f5a652bc-9b59-2358-497d-74d36178ad20@redhat.com>
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Cc: "Burakov, Anatoly" <anatoly.burakov@intel.com>, dev@dpdk.org,
 stable@dpdk.org,
 Jianfeng Tan <jianfeng.tan@intel.com>, "Zhang, Qi Z" <qi.z.zhang@intel.com>,
 Stephen Hemminger <stephen@networkplumber.org>,
 santosh.shukla@caviumnetworks.com,
 Thomas Monjalon <thomas@monjalon.net>, peterx@redhat.com
To: Maxime Coquelin <maxime.coquelin@redhat.com>
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Tested-by: Chas Williams <chas@att.com>

On Fri, Jan 12, 2018 at 8:18 AM, Maxime Coquelin <maxime.coquelin@redhat.com
> wrote:

> Hi Anatoly,
>
>
> On 01/12/2018 12:10 PM, Burakov, Anatoly wrote:
>
>> <snip>
>>
>> +#if defined(RTE_ARCH_X86)
>>> +static bool
>>> +pci_one_device_iommu_support_va(struct rte_pci_device *dev)
>>> +{
>>> +#define VTD_CAP_MGAW_SHIFT    16
>>> +#define VTD_CAP_MGAW_MASK    (0x3fULL << VTD_CAP_MGAW_SHIFT)
>>> +#define X86_VA_WIDTH 47 /* From Documentation/x86/x86_64/mm.txt */
>>> +    struct rte_pci_addr *addr = &dev->addr;
>>> +    char filename[PATH_MAX];
>>> +    FILE *fp;
>>> +    uint64_t mgaw, vtd_cap_reg = 0;
>>> +
>>> +    snprintf(filename, sizeof(filename),
>>> +         "%s/" PCI_PRI_FMT "/iommu/intel-iommu/cap",
>>> +         rte_pci_get_sysfs_path(), addr->domain, addr->bus, addr->devid,
>>> +         addr->function);
>>> +    if (access(filename, F_OK) == -1) {
>>> +        /* We don't have an Intel IOMMU, assume VA supported*/
>>> +        return true;
>>> +    }
>>> +
>>> +    /* We have an intel IOMMU */
>>> +    fp = fopen(filename, "r");
>>> +    if (fp == NULL) {
>>> +        RTE_LOG(ERR, EAL, "%s(): can't open %s\n", __func__, filename);
>>> +        return false;
>>> +    }
>>> +
>>> +    if (fscanf(fp, "%lx", &vtd_cap_reg) != 1) {
>>> +        RTE_LOG(ERR, EAL, "%s(): can't read %s\n", __func__, filename);
>>> +        fclose(fp);
>>> +        return false;
>>> +    }
>>> +
>>> +    fclose(fp);
>>>
>>
>> Hi Maxime,
>>
>> You probably want to use eal_parse_sysfs_value() for this.
>>
>
> I initially planned to use it, but the sysfs value is hexadecimal, but
> not prefixed with "0x". For example:
>
> # cat /sys/devices/pci0000\:00/0000\:00\:02.0/iommu/intel-iommu/cap
> 1c0000c40660462
>
> So strtoul() assumes the value is decimal in this case, as explained in
> its man page:
>
> "
> DESCRIPTION
> <snip\>
> If base is zero or 16, the string may then include a "0x" prefix, and
> the number will be read in base 16; otherwise, a zero base is taken as
> 10 (decimal)
> "
>
> Thanks,
> Maxime
>