Re: [Qemu-devel] [PATCH] e1000e: Do not auto-clear ICR bits which aren't set in EIAC

[Jan Kiszka]

On 2018-06-12 20:11, Philippe Mathieu-Daudé wrote:
> Hi Jan,
> 
> On 06/12/2018 02:22 PM, Jan Kiszka wrote:
>> On 2018-05-22 09:00, Jan Kiszka wrote:
>>> On 2018-04-16 17:29, Peter Maydell wrote:
>>>> On 16 April 2018 at 16:25, Jan Kiszka <address@hidden> wrote:
>>>>> On 2018-04-01 23:17, Jan Kiszka wrote:
>>>>>> From: Jan Kiszka <address@hidden>
>>>>>>
>>>>>> The spec does not justify clearing of any E1000_ICR_OTHER_CAUSES when
>>>>>> E1000_ICR_OTHER is set in EIAC. In fact, removing this code fixes the
>>>>>> issue the Linux driver runs into since 4aea7a5c5e94 ("e1000e: Avoid
>>>>>> receiver overrun interrupt bursts") and was worked around by
>>>>>> 745d0bd3af99 ("e1000e: Remove Other from EIAC").
>>>>>>
>>>>>> Signed-off-by: Jan Kiszka <address@hidden>
>>>>>> ---
>>>>>>
>>>>>> This resolves the issue I reported on February 18 ("e1000e: MSI-X
>>>>>> problem with recent Linux drivers").
>>>>>>
>>>>>>  hw/net/e1000e_core.c | 4 ----
>>>>>>  1 file changed, 4 deletions(-)
>>>>>>
>>>>>> diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
>>>>>> index ecf9b15555..d38f025c0f 100644
>>>>>> --- a/hw/net/e1000e_core.c
>>>>>> +++ b/hw/net/e1000e_core.c
>>>>>> @@ -2022,10 +2022,6 @@ e1000e_msix_notify_one(E1000ECore *core, uint32_t 
>>>>>> cause, uint32_t int_cfg)
>>>>>>
>>>>>>      effective_eiac = core->mac[EIAC] & cause;
>>>>>>
>>>>>> -    if (effective_eiac == E1000_ICR_OTHER) {
>>>>>> -        effective_eiac |= E1000_ICR_OTHER_CAUSES;
>>>>>> -    }
>>>>>> -
>>>>>>      core->mac[ICR] &= ~effective_eiac;
>>>>>>
>>>>>>      if (!(core->mac[CTRL_EXT] & E1000_CTRL_EXT_IAME)) {
>>>>>>
>>>>>
>>>>> Ping for this - as well as https://patchwork.ozlabs.org/patch/895476.
>>>>>
>>>>> Given that q35 uses e1000e by default and many Linux kernel versions no
>>>>> longer work, this should likely go into upcoming and stable versions
>>>>
>>>> I'd rather not put it into 2.12 at this point in the release
>>>> cycle unless it's a regression from 2.11, I think.
>>>
>>> Second ping - nothing hit the repo so far, nor did I receive feedback.
>>>
>>
>> And another ping. For both.
>>
>> These days I had to help someone with a broken QEMU setup that failed
>> installing from network. It turned out that "modprobe e1000e IntMode=0"
>> was needed to workaround the issues my patches address.
> 
> What about the IMS register? It is set just after.
> 
> Looking at b38636b8372, can you test this patch?
> 
> -- >8 --
> diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
> index c93c4661ed..a484b68a5a 100644
> --- a/hw/net/e1000e_core.c
> +++ b/hw/net/e1000e_core.c
> @@ -2022,13 +2022,13 @@ e1000e_msix_notify_one(E1000ECore *core,
> uint32_t cause, uint32_t int_cfg)
> 
>      effective_eiac = core->mac[EIAC] & cause;
> 
> -    if (effective_eiac == E1000_ICR_OTHER) {
> -        effective_eiac |= E1000_ICR_OTHER_CAUSES;
> -    }
> -
>      core->mac[ICR] &= ~effective_eiac;
> 
>      if (!(core->mac[CTRL_EXT] & E1000_CTRL_EXT_IAME)) {
> +        if (effective_eiac == E1000_ICR_OTHER) {
> +            effective_eiac |= E1000_ICR_OTHER_CAUSES;
> +        }
> +
>          core->mac[IMS] &= ~effective_eiac;
>      }
>  }
> 

Before testing this: What would be the reasoning for this change?

I need to refresh my caches, the debugging session is now too long ago
again.

Jan

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