RE: [PATCH v3 06/47] igb: Clear IMS bits when committing ICR access

[Sriram Yagnaraman]

> -----Original Message-----
> From: Akihiko Odaki <akihiko.odaki@daynix.com>
> Sent: Monday, 24 April 2023 12:52
> To: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
> Cc: Jason Wang <jasowang@redhat.com>; Dmitry Fleytman
> <dmitry.fleytman@gmail.com>; Michael S . Tsirkin <mst@redhat.com>; Alex
> Bennée <alex.bennee@linaro.org>; Philippe Mathieu-Daudé
> <philmd@linaro.org>; Thomas Huth <thuth@redhat.com>; Wainer dos Santos
> Moschetta <wainersm@redhat.com>; Beraldo Leal <bleal@redhat.com>;
> Cleber Rosa <crosa@redhat.com>; Laurent Vivier <lvivier@redhat.com>; Paolo
> Bonzini <pbonzini@redhat.com>; qemu-devel@nongnu.org; Tomasz Dzieciol
> <t.dzieciol@partner.samsung.com>
> Subject: Re: [PATCH v3 06/47] igb: Clear IMS bits when committing ICR access
> 
> On 2023/04/24 18:29, Sriram Yagnaraman wrote:
> >> -----Original Message-----
> >> From: Akihiko Odaki <akihiko.odaki@daynix.com>
> >> Sent: Sunday, 23 April 2023 06:18
> >> Cc: Sriram Yagnaraman <sriram.yagnaraman@est.tech>; Jason Wang
> >> <jasowang@redhat.com>; Dmitry Fleytman <dmitry.fleytman@gmail.com>;
> >> Michael S . Tsirkin <mst@redhat.com>; Alex Bennée
> >> <alex.bennee@linaro.org>; Philippe Mathieu-Daudé <philmd@linaro.org>;
> >> Thomas Huth <thuth@redhat.com>; Wainer dos Santos Moschetta
> >> <wainersm@redhat.com>; Beraldo Leal <bleal@redhat.com>; Cleber Rosa
> >> <crosa@redhat.com>; Laurent Vivier <lvivier@redhat.com>; Paolo
> >> Bonzini <pbonzini@redhat.com>; qemu-devel@nongnu.org; Tomasz
> Dzieciol
> >> <t.dzieciol@partner.samsung.com>; Akihiko Odaki
> >> <akihiko.odaki@daynix.com>
> >> Subject: [PATCH v3 06/47] igb: Clear IMS bits when committing ICR
> >> access
> >>
> >> The datasheet says contradicting statements regarding ICR accesses so
> >> it is not reliable to determine the behavior of ICR accesses.
> >> However, e1000e does clear IMS bits when reading ICR accesses and
> >> Linux also expects ICR accesses will clear IMS bits according to:
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tr
> >> ee/drivers/
> >> net/ethernet/intel/igb/igb_main.c?h=v6.2#n8048
> >>
> >> Fixes: 3a977deebe ("Intrdocue igb device emulation")
> >> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> >> ---
> >>   hw/net/igb_core.c | 8 ++++----
> >>   1 file changed, 4 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/hw/net/igb_core.c b/hw/net/igb_core.c index
> >> 96a118b6c1..eaca5bd2b6 100644
> >> --- a/hw/net/igb_core.c
> >> +++ b/hw/net/igb_core.c
> >> @@ -2452,16 +2452,16 @@ igb_set_ims(IGBCore *core, int index,
> >> uint32_t
> >> val)  static void igb_commit_icr(IGBCore *core)  {
> >>       /*
> >> -     * If GPIE.NSICR = 0, then the copy of IAM to IMS will occur only if 
> >> at
> >> +     * If GPIE.NSICR = 0, then the clear of IMS will occur only if
> >> + at
> >>        * least one bit is set in the IMS and there is a true interrupt as
> >>        * reflected in ICR.INTA.
> >>        */
> >>       if ((core->mac[GPIE] & E1000_GPIE_NSICR) ||
> >>           (core->mac[IMS] && (core->mac[ICR] & E1000_ICR_INT_ASSERTED))) {
> >> -        igb_set_ims(core, IMS, core->mac[IAM]);
> >> -    } else {
> >> -        igb_update_interrupt_state(core);
> >> +        igb_clear_ims_bits(core, core->mac[IAM]);
> >>       }
> >> +
> >> +    igb_update_interrupt_state(core);
> >>   }
> >>
> >>   static void igb_set_icr(IGBCore *core, int index, uint32_t val)
> >> --
> >> 2.40.0
> >
> > Reviewed-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
> >
> > An additional question, should ICR be cleared if an actual interrupt was
> asserted?
> > (According to 7.3.2.11 GPIE: Non Selective Interrupt clear on read:
> > When set, every read of ICR clears it. When this bit is cleared, an ICR read
> causes it to be cleared only if an actual interrupt was asserted or IMS = 0b.)
> Something like this?
> 
> That is handled in igb_commit_icr(), which is renamed to igb_nsicr() in patch
> "igb: Notify only new interrupts".
> 

Mm, I must be missing something, but I still don't see the ICR bits being 
cleared igb_commit_icr/igb_nsicr(). 
For e.g. e1000e_mac_icr_read does this explicitly:
    if ((core->mac[ICR] & E1000_ICR_ASSERTED) &&
        (core->mac[CTRL_EXT] & E1000_CTRL_EXT_IAME)) {
        trace_e1000e_irq_icr_clear_iame();
        core->mac[ICR] = 0;
        trace_e1000e_irq_icr_process_iame();
        e1000e_clear_ims_bits(core, core->mac[IAM]);
    }


> >
> > diff --git a/hw/net/igb_core.c b/hw/net/igb_core.c index
> > eaca5bd2b6..aaaf80e4a3 100644
> > --- a/hw/net/igb_core.c
> > +++ b/hw/net/igb_core.c
> > @@ -2529,6 +2529,9 @@ igb_mac_icr_read(IGBCore *core, int index)
> >       } else if (core->mac[IMS] == 0) {
> >           trace_e1000e_irq_icr_clear_zero_ims();
> >           core->mac[ICR] = 0;
> > +    } else if (core->mac[ICR] & E1000_ICR_INT_ASSERTED) {
> > +        e1000e_irq_icr_clear_iame();
> > +        core->mac[ICR] = 0;
> >       } else if (!msix_enabled(core->owner)) {
> >           trace_e1000e_irq_icr_clear_nonmsix_icr_read();
> >           core->mac[ICR] = 0;