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Re: [PATCH] x86/hvm: Advertise and support extended destination IDs for MSI/IO-APIC
- To: Julian Vetter <julian.vetter@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 9 Feb 2026 15:10:04 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 09 Feb 2026 14:10:14 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 09.02.2026 12:34, Julian Vetter wrote:
> --- a/xen/arch/x86/include/asm/hvm/vioapic.h
> +++ b/xen/arch/x86/include/asm/hvm/vioapic.h
> @@ -32,6 +32,19 @@
> #define VIOAPIC_EDGE_TRIG 0
> #define VIOAPIC_LEVEL_TRIG 1
>
> +/*
> + * Extract the destination ID from a 64-bit IO-APIC RTE, including the
> + * extended bits (55:49) used when XEN_HVM_CPUID_EXT_DEST_ID is advertised.
> + */
> +#define IO_APIC_REDIR_DEST_SHIFT 56
> +#define IO_APIC_REDIR_DEST_MASK 0xffULL
> +#define IO_APIC_REDIR_EXT_DEST_SHIFT 49
> +#define IO_APIC_REDIR_EXT_DEST_MASK 0x7fULL
Can we please stop introducing pairs of mask and shift values? Already these
versus ...
> --- a/xen/arch/x86/include/asm/msi.h
> +++ b/xen/arch/x86/include/asm/msi.h
> @@ -54,6 +54,9 @@
> #define MSI_ADDR_DEST_ID_MASK 0x00ff000
> #define MSI_ADDR_DEST_ID(dest) (((dest) <<
> MSI_ADDR_DEST_ID_SHIFT) & MSI_ADDR_DEST_ID_MASK)
>
> +#define MSI_ADDR_EXT_DEST_ID_SHIFT 5
> +#define MSI_ADDR_EXT_DEST_ID_MASK 0x0000fe0
... this shows one of the problems: It's never clear whether the mask is
intended to be applied to the shifted or un-shifted value. Like you have it
down here, the mask constant alone is enough. You use it with MASK_EXTR()
and MASK_INSR().
Jan
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