x86/ioapic: Generate RTE directly from parent irqchip's MSI message

The I/O-APIC generates an MSI cycle with address/data bits taken from its
Redirection Table Entry in some combination which used to make sense, but
now is just a bunch of bits which get passed through in some seemingly
arbitrary order.

Instead of making IRQ remapping drivers directly frob the I/OA-PIC RTE, let
them just do their job and generate an MSI message. The bit swizzling to
turn that MSI message into the I/O-APIC's RTE is the same in all cases,
since it's a function of the I/O-APIC hardware. The IRQ remappers have no
real need to get involved with that.

The only slight caveat is that the I/OAPIC is interpreting some of those
fields too, and it does want the 'vector' field to be unique to make EOI
work. The AMD IOMMU happens to put its IRTE index in the bits that the
I/O-APIC thinks are the vector field, and accommodates this requirement by
reserving the first 32 indices for the I/O-APIC.  The Intel IOMMU doesn't
actually use the bits that the I/O-APIC thinks are the vector field, so it
fills in the 'pin' value there instead.

[ tglx: Replaced the unreadably macro maze with the cleaned up RTE/msi_msg
  	bitfields and added commentry to explain the mapping magic ]

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201024213535.443185-22-dwmw2@infradead.org

1 files changed, 5 insertions, 6 deletions

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 517847a94dbe..83a69f62637e 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -45,12 +45,11 @@ enum irq_alloc_type {
 };
 
 struct ioapic_alloc_info {
-	int				pin;
-	int				node;
-	u32				is_level	: 1;
-	u32				active_low	: 1;
-	u32				valid		: 1;
-	struct IO_APIC_route_entry	*entry;
+	int		pin;
+	int		node;
+	u32		is_level	: 1;
+	u32		active_low	: 1;
+	u32		valid		: 1;
 };
 
 struct uv_alloc_info {