From: David Woodhouse <d...@amazon.co.uk>
Some hypervisors can allow the guest to use the Extended Destination ID
field in the IOAPIC RTE and MSI address to address up to 32768 CPUs.
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
---
arch/x86/include/asm/mpspec.h | 1 +
arch/x86/include/asm/x86_init.h | 2 ++
arch/x86/kernel/apic/apic.c | 15 ++++++++++++++-
arch/x86/kernel/apic/msi.c | 9 ++++++++-
arch/x86/kernel/x86_init.c | 1 +
5 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
index e90ac7e9ae2c..25ee8ca0a1f2 100644
--- a/arch/x86/include/asm/mpspec.h
+++ b/arch/x86/include/asm/mpspec.h
@@ -42,6 +42,7 @@ extern DECLARE_BITMAP(mp_bus_not_pci, MAX_MP_BUSSES);
extern unsigned int boot_cpu_physical_apicid;
extern u8 boot_cpu_apic_version;
extern unsigned long mp_lapic_addr;
+extern int msi_ext_dest_id;
#ifdef CONFIG_X86_LOCAL_APIC
extern int smp_found_config;
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 397196fae24d..5af3fe9e38f3 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -114,6 +114,7 @@ struct x86_init_pci {
* @init_platform: platform setup
* @guest_late_init: guest late init
* @x2apic_available: X2APIC detection
+ * @msi_ext_dest_id: MSI and IOAPIC support 15-bit APIC IDs
* @init_mem_mapping: setup early mappings during init_mem_mapping()
* @init_after_bootmem: guest init after boot allocator is
finished
*/
@@ -121,6 +122,7 @@ struct x86_hyper_init {
void (*init_platform)(void);
void (*guest_late_init)(void);
bool (*x2apic_available)(void);
+ bool (*msi_ext_dest_id)(void);
void (*init_mem_mapping)(void);
void (*init_after_bootmem)(void);
};
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index a75767052a92..459c78558f36 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1837,6 +1837,8 @@ static __init void x2apic_enable(void)
static __init void try_to_enable_x2apic(int remap_mode)
{
+ u32 apic_limit = 0;
+
if (x2apic_state == X2APIC_DISABLED)
return;
@@ -1858,7 +1860,15 @@ static __init void try_to_enable_x2apic(int remap_mode)
return;
}
- x2apic_set_max_apicid(255);
+ /*
+ * If the hypervisor supports extended destination ID
+ * in IOAPIC and MSI, we can support that many CPUs.
+ */
+ if (x86_init.hyper.msi_ext_dest_id()) {
+ msi_ext_dest_id = 1;
+ apic_limit = 32767;
+ } else
+ apic_limit = 255;
}
/*
@@ -1867,6 +1877,9 @@ static __init void try_to_enable_x2apic(int remap_mode)
*/
x2apic_phys = 1;
}
+ if (apic_limit)
+ x2apic_set_max_apicid(apic_limit);
+
x2apic_enable();
}
diff --git a/arch/x86/kernel/apic/msi.c b/arch/x86/kernel/apic/msi.c
index 356f8acf4927..4d891967bea4 100644
--- a/arch/x86/kernel/apic/msi.c
+++ b/arch/x86/kernel/apic/msi.c
@@ -23,6 +23,8 @@
struct irq_domain *x86_pci_msi_default_domain __ro_after_init;
+int msi_ext_dest_id __ro_after_init;
+
static void __irq_msi_compose_msg(struct irq_cfg *cfg, struct msi_msg *msg,
int dmar)
{
msg->address_hi = MSI_ADDR_BASE_HI;
@@ -45,10 +47,15 @@ static void __irq_msi_compose_msg(struct irq_cfg *cfg,
struct msi_msg *msg, int
* Only the IOMMU itself can use the trick of putting destination
* APIC ID into the high bits of the address. Anything else would
* just be writing to memory if it tried that, and needs IR to
- * address APICs above 255.
+ * address APICs which can't be addressed in the normal 32-bit
+ * address range at 0xFFExxxxx. That is typically just 8 bits, but
+ * some hypervisors allow the extended destination ID field in bits
+ * 11-5 to be used, giving support for 15 bits of APIC IDs in total.
*/
if (dmar)
msg->address_hi |= MSI_ADDR_EXT_DEST_ID(cfg->dest_apicid);
+ else if (msi_ext_dest_id && cfg->dest_apicid < 0x8000)
+ msg->address_lo |= MSI_ADDR_EXT_DEST_ID(cfg->dest_apicid) >> 3;
else
WARN_ON_ONCE(MSI_ADDR_EXT_DEST_ID(cfg->dest_apicid));
}
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index a3038d8deb6a..8b395821cb8d 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -110,6 +110,7 @@ struct x86_init_ops x86_init __initdata = {
.init_platform = x86_init_noop,
.guest_late_init = x86_init_noop,
.x2apic_available = bool_x86_init_noop,
+ .msi_ext_dest_id = bool_x86_init_noop,
.init_mem_mapping = x86_init_noop,
.init_after_bootmem = x86_init_noop,
},
--
2.26.2
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