[PATCH 1/1] OvmfPkg/PciHotPlugInitDxe: Do not reserve IO ports by default.

[PATCH 1/1] OvmfPkg/PciHotPlugInitDxe: Do not reserve IO ports by default.

[Gerd Hoffmann]

Flip the default for IO address space reservations for PCI(e) bridges
and root ports with hotplug support from TRUE to FALSE.

PCI(e) bridges will still get IO address space assigned in case:

  (a) Downstream devices actually need IO address space, or
  (b) Explicit configuration, using "qemu -device
      pcie-root-port,io-reserve=<size>".

In case IO address space is exhausted edk2 will stop assigning resources
to PCI(e) bridges.  This is not limited to IO resources, the affected
bridges will not get any memory resources assigned either.

This patch solves this issue by not handing out the scare IO address
space, which is in most cases not needed anyway.  Result is a more
consistent PCI configuration in virtual machine configurations with many
PCie root ports.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
index 6b2b6797b3b6..69903a600981 100644
--- a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
+++ b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
@@ -589,7 +589,7 @@ GetResourcePadding (
     return EFI_INVALID_PARAMETER;
   }
 
-  DefaultIo       = TRUE;
+  DefaultIo       = FALSE;
   DefaultMmio     = TRUE;
   DefaultPrefMmio = TRUE;
 
-- 
2.40.1

Re: [PATCH 1/1] OvmfPkg/PciHotPlugInitDxe: Do not reserve IO ports by default.

[Ard Biesheuvel]

On Tue, 16 May 2023 at 11:48, Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> Flip the default for IO address space reservations for PCI(e) bridges
> and root ports with hotplug support from TRUE to FALSE.
>
> PCI(e) bridges will still get IO address space assigned in case:
>
>   (a) Downstream devices actually need IO address space, or
>   (b) Explicit configuration, using "qemu -device
>       pcie-root-port,io-reserve=<size>".
>
> In case IO address space is exhausted edk2 will stop assigning resources
> to PCI(e) bridges.  This is not limited to IO resources, the affected
> bridges will not get any memory resources assigned either.
>
> This patch solves this issue by not handing out the scare IO address
> space, which is in most cases not needed anyway.  Result is a more
> consistent PCI configuration in virtual machine configurations with many
> PCie root ports.
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>  OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
> index 6b2b6797b3b6..69903a600981 100644
> --- a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
> +++ b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
> @@ -589,7 +589,7 @@ GetResourcePadding (
>      return EFI_INVALID_PARAMETER;
>    }
>
> -  DefaultIo       = TRUE;
> +  DefaultIo       = FALSE;
>    DefaultMmio     = TRUE;
>    DefaultPrefMmio = TRUE;
>
> --
> 2.40.1
>

Re: [PATCH 1/1] OvmfPkg/PciHotPlugInitDxe: Do not reserve IO ports by default.

[Ard Biesheuvel]

On Thu, 25 May 2023 at 17:47, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Tue, 16 May 2023 at 11:48, Gerd Hoffmann <kraxel@redhat.com> wrote:
> >
> > Flip the default for IO address space reservations for PCI(e) bridges
> > and root ports with hotplug support from TRUE to FALSE.
> >
> > PCI(e) bridges will still get IO address space assigned in case:
> >
> >   (a) Downstream devices actually need IO address space, or
> >   (b) Explicit configuration, using "qemu -device
> >       pcie-root-port,io-reserve=<size>".
> >
> > In case IO address space is exhausted edk2 will stop assigning resources
> > to PCI(e) bridges.  This is not limited to IO resources, the affected
> > bridges will not get any memory resources assigned either.
> >
> > This patch solves this issue by not handing out the scare IO address
> > space, which is in most cases not needed anyway.  Result is a more
> > consistent PCI configuration in virtual machine configurations with many
> > PCie root ports.
> >
> > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>
> Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
>

Merged as #4441

> > ---
> >  OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
> > index 6b2b6797b3b6..69903a600981 100644
> > --- a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
> > +++ b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
> > @@ -589,7 +589,7 @@ GetResourcePadding (
> >      return EFI_INVALID_PARAMETER;
> >    }
> >
> > -  DefaultIo       = TRUE;
> > +  DefaultIo       = FALSE;
> >    DefaultMmio     = TRUE;
> >    DefaultPrefMmio = TRUE;
> >
> > --
> > 2.40.1
> >