Messages in this thread | | | Subject | Re: [RFC 1/2] vhost: IFC VF hardware operation layer | From | Zhu Lingshan <> | Date | Tue, 22 Oct 2019 14:48:43 +0800 |
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On 10/22/2019 9:32 AM, Jason Wang wrote: > > On 2019/10/22 上午12:31, Simon Horman wrote: >> On Mon, Oct 21, 2019 at 05:55:33PM +0800, Zhu, Lingshan wrote: >>> On 10/16/2019 5:53 PM, Simon Horman wrote: >>>> Hi Zhu, >>>> >>>> thanks for your patch. >>>> >>>> On Wed, Oct 16, 2019 at 09:10:40AM +0800, Zhu Lingshan wrote: >> ... >> >>>>> +static void ifcvf_read_dev_config(struct ifcvf_hw *hw, u64 offset, >>>>> + void *dst, int length) >>>>> +{ >>>>> + int i; >>>>> + u8 *p; >>>>> + u8 old_gen, new_gen; >>>>> + >>>>> + do { >>>>> + old_gen = ioread8(&hw->common_cfg->config_generation); >>>>> + >>>>> + p = dst; >>>>> + for (i = 0; i < length; i++) >>>>> + *p++ = ioread8((u8 *)hw->dev_cfg + offset + i); >>>>> + >>>>> + new_gen = ioread8(&hw->common_cfg->config_generation); >>>>> + } while (old_gen != new_gen); >>>> Would it be wise to limit the number of iterations of the loop above? >>> Thanks but I don't quite get it. This is used to make sure the function >>> would get the latest config. >> I am worried about the possibility that it will loop forever. >> Could that happen? >> >> ... > > > My understanding is that the function here is similar to virtio config > generation [1]. So this can only happen for a buggy hardware. > > Thanks > > [1] > https://docs.oasis-open.org/virtio/virtio/v1.1/csprd01/virtio-v1.1-csprd01.html > Section 2.4.1 Yes! > > >> >>>>> +static void io_write64_twopart(u64 val, u32 *lo, u32 *hi) >>>>> +{ >>>>> + iowrite32(val & ((1ULL << 32) - 1), lo); >>>>> + iowrite32(val >> 32, hi); >>>>> +} >>>> I see this macro is also in virtio_pci_modern.c >>>> >>>> Assuming lo and hi aren't guaranteed to be sequential >>>> and thus iowrite64_hi_lo() cannot be used perhaps >>>> it would be good to add a common helper somewhere. >>> Thanks, I will try after this IFC patchwork, I will cc you. >> Thanks. >> >> ... >
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