[PATCH v3 31/35] x86/ioapic: Handle Extended Destination ID field in RTE

David Woodhouse
2020-10-24T21:36:14Z

From: David Woodhouse <dwmw@amazon.co.uk>

Bits 63-48 of the I/OAPIC Redirection Table Entry map directly to bits 19-4
of the address used in the resulting MSI cycle.

Historically, the x86 MSI format only used the top 8 of those 16 bits as
the destination APIC ID, and the "Extended Destination ID" in the lower 8
bits was unused.

With interrupt remapping, the lowest bit of the Extended Destination ID
(bit 48 of RTE, bit 4 of MSI address) is now used to indicate a remappable
format MSI.

A hypervisor can use the other 7 bits of the Extended Destination ID to
permit guests to address up to 15 bits of APIC IDs, thus allowing 32768
vCPUs before having to expose a vIOMMU and interrupt remapping to the
guest.

No behavioural change in this patch, since nothing yet permits APIC IDs
above 255 to be used with the non-IR I/OAPIC domain.

[ tglx: Converted it to the cleaned up entry/msi_msg format and added
commentry ]

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/io_apic.h | 3 ++-
arch/x86/kernel/apic/io_apic.c | 20 +++++++++++++++-----
2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index 73da644b2f0d..437aa8d00e53 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -67,7 +67,8 @@ struct IO_APIC_route_entry {
is_level : 1,
masked : 1,
reserved_0 : 15,
- reserved_1 : 24,
+ reserved_1 : 17,
+ virt_destid_8_14 : 7,
destid_0_7 : 8;
};
struct {
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 443d2c9086b9..1cfd65ef295b 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1238,9 +1238,10 @@ static void io_apic_print_entries(unsigned int apic, unsigned int nr_entries)
(entry.ir_index_15 << 15) | entry.ir_index_0_14,
entry.ir_zero);
} else {
- printk(KERN_DEBUG "%s, %s, D(%02X), M(%1d)\n", buf,
+ printk(KERN_DEBUG "%s, %s, D(%02X%02X), M(%1d)\n", buf,
entry.dest_mode_logical ? "logical " : "physical",
- entry.destid_0_7, entry.delivery_mode);
+ entry.virt_destid_8_14, entry.destid_0_7,
+ entry.delivery_mode);
}
}
}
@@ -1409,6 +1410,7 @@ void native_restore_boot_irq_mode(void)
*/
if (ioapic_i8259.pin != -1) {
struct IO_APIC_route_entry entry;
+ u32 apic_id = read_apic_id();

memset(&entry, 0, sizeof(entry));
entry.masked = false;
@@ -1416,7 +1418,8 @@ void native_restore_boot_irq_mode(void)
entry.active_low = false;
entry.dest_mode_logical = false;
entry.delivery_mode = APIC_DELIVERY_MODE_EXTINT;
- entry.destid_0_7 = read_apic_id();
+ entry.destid_0_7 = apic_id & 0xFF;
+ entry.virt_destid_8_14 = apic_id >> 8;

/*
* Add it to the IO-APIC irq-routing table:
@@ -1885,7 +1888,11 @@ static void ioapic_setup_msg_from_msi(struct irq_data *irq_data,
/* DMAR/IR: 1, 0 for all other modes */
entry->ir_format = msg.arch_addr_lo.dmar_format;
/*
- * DMAR/IR: index bit 0-14.
+ * - DMAR/IR: index bit 0-14.
+ *
+ * - Virt: If the host supports x2apic without a virtualized IR
+ * unit then bit 0-6 of dmar_index_0_14 are providing bit
+ * 8-14 of the destination id.
*
* All other modes have bit 0-6 of dmar_index_0_14 cleared and the
* topmost 8 bits are destination id bit 0-7 (entry::destid_0_7).
@@ -2063,6 +2070,7 @@ static inline void __init unlock_ExtINT_logic(void)
int apic, pin, i;
struct IO_APIC_route_entry entry0, entry1;
unsigned char save_control, save_freq_select;
+ u32 apic_id;

pin = find_isa_irq_pin(8, mp_INT);
if (pin == -1) {
@@ -2078,11 +2086,13 @@ static inline void __init unlock_ExtINT_logic(void)
entry0 = ioapic_read_entry(apic, pin);
clear_IO_APIC_pin(apic, pin);

+ apic_id = hard_smp_processor_id();
memset(&entry1, 0, sizeof(entry1));

entry1.dest_mode_logical = true;
entry1.masked = false;
- entry1.destid_0_7 = hard_smp_processor_id();
+ entry1.destid_0_7 = apic_id & 0xFF;
+ entry1.virt_destid_8_14 = apic_id >> 8;
entry1.delivery_mode = APIC_DELIVERY_MODE_EXTINT;
entry1.active_low = entry0.active_low;
entry1.is_level = false;