lkml.org 
[lkml]   [2023]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH 3/7] iommu/vt-d: Support Enhanced Command Interface
    From
    On 2023/1/13 21:55, Baolu Lu wrote:
    >> +/*
    >> + * Function to submit a command to the enhanced command interface. The
    >> + * valid enhanced command descriptions are defined in Table 47 of the
    >> + * VT-d spec. The VT-d hardware implementation may support some but not
    >> + * all commands, which can be determined by checking the Enhanced
    >> + * Command Capability Register.
    >> + *
    >> + * Return values:
    >> + *  - 0: Command successful without any error;
    >> + *  - Negative: software error value;
    >> + *  - Nonzero positive: failure status code defined in Table 48.
    >> + */
    >> +int ecmd_submit_sync(struct intel_iommu *iommu, u8 ecmd,
    >> +             u64 oa, bool has_ob, u64 ob)
    >> +{
    >> +    unsigned long flags;
    >> +    u64 res;
    >> +    int ret;
    >> +
    >> +    if (!cap_ecmds(iommu->cap))
    >> +        return -ENODEV;
    >> +
    >> +    raw_spin_lock_irqsave(&iommu->register_lock, flags);
    >> +
    >> +    res = dmar_readq(iommu->reg + DMAR_ECRSP_REG);
    >> +    if (res & DMA_ECMD_ECRSP_IP) {
    >> +        ret = -EBUSY;
    >> +        goto err;
    >> +    }
    >> +
    >> +    if (has_ob)
    >> +        dmar_writeq(iommu->reg + DMAR_ECEO_REG, ob);
    >
    > The ecmds that require a Operand B are statically defined in the spec,
    > right? What will it look like if we define a static ignore_ob(ecmd)?

    Or simply remove has_ob parameter? The least case is an unnecessary
    write to a register. It's fine as far as I can see since we should avoid
    using it in any critical path.

    --
    Best regards,
    baolu

    \
     
     \ /
      Last update: 2023-03-26 23:39    [W:2.170 / U:0.908 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site