On Mon, Jul 25, 2016 at 07:36:24PM +0800, Peter Xu wrote:
> IOMMU IR and IOAPIC legacy devices (e.g., e1000) cannot work well
> together with some old Linux kernels (upstream before v4.0, or any
> released RHEL kernels). This patch fixes it.
>
> The problem is that: some old linux kernels (with IR enabled) only
> support IOAPIC chips with version 0x20. New kernels after commit d32932d
> ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces")
> fixed this problem. To make sure we can work with even old kernels,
> let's upgrade our IOAPIC to version 0x20.
>
> This patch is only useful when vIOMMU IR is enabled (which still do not
> support kernel IOAPIC). So here we are only upgrading QEMU IOAPIC chip
> to version 0x20. For kernel based IOAPIC, the version will still be
> 0x11.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
As a minimum, we need to make sure not to change this for
old machine types.
Given the timing, limiting this for when IR is enabled
would be a good idea I think.
> ---
> hw/intc/ioapic.c | 6 ++++++
> include/hw/i386/ioapic_internal.h | 3 ++-
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
> index 2d3282a..361c37c 100644
> --- a/hw/intc/ioapic.c
> +++ b/hw/intc/ioapic.c
> @@ -354,6 +354,12 @@ ioapic_mem_write(void *opaque, hwaddr addr, uint64_t val,
> }
> }
> break;
> + case IOAPIC_EOI:
> + if (size != 4) {
> + break;
> + }
> + ioapic_eoi_broadcast(val);
> + break;
> }
>
> ioapic_update_kvm_routes(s);
I'd add a code comment saying this is for 0x20 only.
> diff --git a/include/hw/i386/ioapic_internal.h
> b/include/hw/i386/ioapic_internal.h
> index d89ea1b..9654a93 100644
> --- a/include/hw/i386/ioapic_internal.h
> +++ b/include/hw/i386/ioapic_internal.h
> @@ -29,7 +29,7 @@
>
> #define MAX_IOAPICS 1
>
> -#define IOAPIC_VERSION 0x11
> +#define IOAPIC_VERSION 0x20
>
> #define IOAPIC_LVT_DEST_SHIFT 56
> #define IOAPIC_LVT_DEST_IDX_SHIFT 48
> @@ -71,6 +71,7 @@
>
> #define IOAPIC_IOREGSEL 0x00
> #define IOAPIC_IOWIN 0x10
> +#define IOAPIC_EOI 0x40
>
> #define IOAPIC_REG_ID 0x00
> #define IOAPIC_REG_VER 0x01
> --
> 2.4.11
>
