Re: [PATCH v4 24/27] hw/intc/ioapic: Remove IOAPICCommonState::version field

[Zhao Liu]

On Thu, May 08, 2025 at 03:35:47PM +0200, Philippe Mathieu-Daudé wrote:
> Date: Thu,  8 May 2025 15:35:47 +0200
> From: Philippe Mathieu-Daudé <philmd@linaro.org>
> Subject: [PATCH v4 24/27] hw/intc/ioapic: Remove IOAPICCommonState::version
>  field
> X-Mailer: git-send-email 2.47.1
> 
> The IOAPICCommonState::version integer was only set
> in the hw_compat_2_7[] array, via the 'version=0x11'
> property. We removed all machines using that array,
> lets remove that property, simplify by only using the
> default version (defined as IOAPIC_VER_DEF).
> 
> For the record, this field was introduced in commit
> 20fd4b7b6d9 ("x86: ioapic: add support for explicit EOI"):
> 
>  >   Some old Linux kernels (upstream before v4.0), or any released RHEL
>  >   kernels has problem in sending APIC EOI when IR is enabled.
>  >   Meanwhile, many of them only support explicit EOI for IOAPIC, which
>  >   is only introduced in IOAPIC version 0x20. This patch provide a way
>  >   to boost QEMU IOAPIC to version 0x20, in order for QEMU to correctly
>  >   receive EOI messages.
>  >
>  >   Without boosting IOAPIC version to 0x20, kernels before commit
>  >   d32932d ("x86/irq: Convert IOAPIC to use hierarchical irqdomain
>  >   interfaces") will have trouble enabling both IR and level-triggered
>  >   interrupt devices (like e1000).
>  >
>  >   To upgrade IOAPIC to version 0x20, we need to specify:
>  >
>  >     -global ioapic.version=0x20
>  >
>  >   To be compatible with old systems, 0x11 will still be the default
>  >   IOAPIC version. Here 0x11 and 0x20 are the only versions to be
>  >   supported.
>  >
>  >   One thing to mention: this patch only applies to emulated IOAPIC. It
>  >   does not affect kernel IOAPIC behavior.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
> ---
>  hw/intc/ioapic_internal.h |  3 +--
>  hw/intc/ioapic.c          | 18 ++----------------
>  hw/intc/ioapic_common.c   |  2 +-
>  3 files changed, 4 insertions(+), 19 deletions(-)

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>