Re: [PATCH 2/3] hw/net: e1000e: Correct the initial value of VET register

[Bin Meng]

On Fri, Jul 2, 2021 at 1:47 PM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2021/7/2 下午12:43, Bin Meng 写道:
> > On Fri, Jul 2, 2021 at 11:29 AM Jason Wang <jasowang@redhat.com> wrote:
> >>
> >> 在 2021/7/1 下午5:46, Bin Meng 写道:
> >>> From: Christina Wang <christina.wang@windriver.com>
> >>>
> >>> The initial value of VLAN Ether Type (VET) register is 0x8100, as per
> >>> the manual and real hardware.
> >>>
> >>> While Linux e1000e driver always writes VET register to 0x8100, it is
> >>> not always the case for everyone. Drivers relying on the reset value
> >>> of VET won't be able to transmit and receive VLAN frames in QEMU.
> >>>
> >>> Unlike e1000 in QEMU, e1000e uses a field 'vet' in "struct E1000Core"
> >>> to cache the value of VET register, but the cache only gets updated
> >>> when VET register is written. To always get a consistent VET value
> >>> no matter VET is written or remains its reset value, drop the 'vet'
> >>> field and use 'core->mac[VET]' directly.
> >>>
> >>> Reported-by: Markus Carlstedt <markus.carlstedt@windriver.com>
> >>> Signed-off-by: Christina Wang <christina.wang@windriver.com>
> >>> Signed-off-by: Bin Meng <bin.meng@windriver.com>
> >>> Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
> >>> ---
> >>>
> >>>    hw/net/e1000e_core.h |  2 --
> >>>    hw/net/e1000e.c      |  6 ++----
> >>>    hw/net/e1000e_core.c | 11 ++++++-----
> >>>    3 files changed, 8 insertions(+), 11 deletions(-)
> >>>
> >>> diff --git a/hw/net/e1000e_core.h b/hw/net/e1000e_core.h
> >>> index 4ddb4d2c39..07d722bc68 100644
> >>> --- a/hw/net/e1000e_core.h
> >>> +++ b/hw/net/e1000e_core.h
> >>> @@ -105,8 +105,6 @@ struct E1000Core {
> >>>        uint32_t itr_guest_value;
> >>>        uint32_t eitr_guest_value[E1000E_MSIX_VEC_NUM];
> >>>
> >>> -    uint16_t vet;
> >>> -
> >>>        uint8_t permanent_mac[ETH_ALEN];
> >>>
> >>>        NICState *owner_nic;
> >>> diff --git a/hw/net/e1000e.c b/hw/net/e1000e.c
> >>> index a8a77eca95..1797e4a7cb 100644
> >>> --- a/hw/net/e1000e.c
> >>> +++ b/hw/net/e1000e.c
> >>> @@ -602,8 +602,8 @@ static const VMStateDescription 
> >>> e1000e_vmstate_intr_timer = {
> >>>
> >>>    static const VMStateDescription e1000e_vmstate = {
> >>>        .name = "e1000e",
> >>> -    .version_id = 1,
> >>> -    .minimum_version_id = 1,
> >>> +    .version_id = 2,
> >>> +    .minimum_version_id = 2,
> >>>        .pre_save = e1000e_pre_save,
> >>>        .post_load = e1000e_post_load,
> >>>        .fields = (VMStateField[]) {
> >>> @@ -645,8 +645,6 @@ static const VMStateDescription e1000e_vmstate = {
> >>>            VMSTATE_UINT32_ARRAY(core.eitr_guest_value, E1000EState,
> >>>                                 E1000E_MSIX_VEC_NUM),
> >>>
> >>> -        VMSTATE_UINT16(core.vet, E1000EState),
> >>
> >> This is not the suggested way. We'd better not bump version in this case.
> >>
> >> How about update vet during post_load?
> > But core.vet is removed in this patch. Not sure how to handle this?
>
>
> Keep using core.vet, sync core.vet with mac[VET] during post_load.
>

But keeping using core.vet in the e1000e_core.c will cause mismatch
with mac[VET] as the commit message says.

We can still keep the 'vet' field in the "struct E1000Core", and keep
the "VMSTATE_UINT16(core.vet, E1000EState)" here, but it is useless in
the new code.

Regards,
Bin