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Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment |
Date: |
Tue, 13 Jun 2023 04:51:15 -0400 |
On Tue, Jun 13, 2023 at 09:46:53AM +0200, Bernhard Beschow wrote:
> On Mon, Jun 12, 2023 at 3:01 PM Igor Mammedov <imammedo@redhat.com> wrote:
>
> On Sun, 11 Jun 2023 12:33:59 +0200
> Bernhard Beschow <shentey@gmail.com> wrote:
>
> > Fixes the following clangd warning (-Winitializer-overrides):
> >
> > q35.c:297:19: Initializer overrides prior initialization of this
> subobject
> > q35.c:292:19: previous initialization is here
> >
> > Settle on native endian which causes the least overhead.
> indeed it doesn't matter which way we read all ones, so that should work.
> but does it really matter (I mean the overhead/what workload)?
> If not, I'd prefer explicit LE as it's now to be consistent
> the the rest of memops on Q35.
>
>
> I got a comment from Michael about this in [1], so I've changed it. I don't
> mind changing it either way.
>
> Best regards,
> Bernhard
>
> [1] https://patchew.org/QEMU/20230214131441.101760-1-shentey@gmail.com/
> 20230214131441.101760-3-shentey@gmail.com/#
> 20230301164339-mutt-send-email-mst@kernel.org
Hmm it's not terribly important, and the optimization is trivial,
but yes people tend to copy code, good point. Maybe add a comment?
/*
* Note: don't copy this! normally use DEVICE_LITTLE_ENDIAN. This only
* works because we don't allow writes and always read all-ones.
*/
>
> >
> > Fixes: bafc90bdc594 ("q35: implement TSEG")
> > Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> > ---
> > hw/pci-host/q35.c | 1 -
> > 1 file changed, 1 deletion(-)
> >
> > diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
> > index fd18920e7f..859c197f25 100644
> > --- a/hw/pci-host/q35.c
> > +++ b/hw/pci-host/q35.c
> > @@ -290,7 +290,6 @@ static const MemoryRegionOps blackhole_ops = {
> > .valid.max_access_size = 4,
> > .impl.min_access_size = 4,
> > .impl.max_access_size = 4,
> > - .endianness = DEVICE_LITTLE_ENDIAN,
> > };
> >
> > /* PCIe MMCFG */
>
>
- [PATCH 00/15] Q35 and I440FX host bridge QOM cleanup, Bernhard Beschow, 2023/06/11
- [PATCH 01/15] hw/i386/pc_q35: Resolve redundant q35_host variable, Bernhard Beschow, 2023/06/11
- [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, Bernhard Beschow, 2023/06/11
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, Igor Mammedov, 2023/06/12
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, Bernhard Beschow, 2023/06/13
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment,
Michael S. Tsirkin <=
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, BALATON Zoltan, 2023/06/13
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, Igor Mammedov, 2023/06/13
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, Philippe Mathieu-Daudé, 2023/06/13
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, Michael S. Tsirkin, 2023/06/13
- Re: [PATCH 02/15] hw/pci-host/q35: Fix double, contradicting .endianness assignment, Bernhard Beschow, 2023/06/13
[PATCH 03/15] hw/pci-host/q35: Initialize PCMachineState::bus in board code, Bernhard Beschow, 2023/06/11
[PATCH 04/15] hw/pci/pci_host: Introduce PCI_HOST_BYPASS_IOMMU macro, Bernhard Beschow, 2023/06/11