[PATCH v3 2/4] x86/ioapic: RTE modifications must use ioapic_write_entry

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Do not allow to write to RTE registers using io_apic_write and instead
require changes to RTE to be performed using ioapic_write_entry.

This is in preparation for passing the full contents of the RTE to the
IOMMU interrupt remapping handlers, so remapping entries for IO-APIC
RTEs can be updated atomically when possible.

While immediately this commit might expand the number of MMIO accesses
in order to update an IO-APIC RTE, further changes will benefit from
getting the full RTE value passed to the IOMMU handlers, as the logic
is greatly simplified when the IOMMU handlers can get the complete RTE
value in one go.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v2:
 - Also adjust __ioapic_read_entry().

Changes since v1:
 - Reinstate io_apic_modify().
 - Expand commit message.
---
 xen/arch/x86/include/asm/io_apic.h       |  8 ++---
 xen/arch/x86/io_apic.c                   | 43 ++++++++++++------------
 xen/drivers/passthrough/amd/iommu_intr.c |  6 ----
 3 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/xen/arch/x86/include/asm/io_apic.h 
b/xen/arch/x86/include/asm/io_apic.h
index 4c4777b68a51..9165da2281ae 100644
--- a/xen/arch/x86/include/asm/io_apic.h
+++ b/xen/arch/x86/include/asm/io_apic.h
@@ -162,8 +162,8 @@ static inline void __io_apic_write(unsigned int apic, 
unsigned int reg, unsigned
 
 static inline void io_apic_write(unsigned int apic, unsigned int reg, unsigned 
int value)
 {
-    if ( ioapic_reg_remapped(reg) )
-        return iommu_update_ire_from_apic(apic, reg, value);
+    /* RTE writes must use ioapic_write_entry. */
+    BUG_ON(reg >= 0x10);
     __io_apic_write(apic, reg, value);
 }
 
@@ -173,8 +173,8 @@ static inline void io_apic_write(unsigned int apic, 
unsigned int reg, unsigned i
  */
 static inline void io_apic_modify(unsigned int apic, unsigned int reg, 
unsigned int value)
 {
-    if ( ioapic_reg_remapped(reg) )
-        return iommu_update_ire_from_apic(apic, reg, value);
+    /* RTE writes must use ioapic_write_entry. */
+    BUG_ON(reg >= 0x10);
     *(IO_APIC_BASE(apic) + 4) = value;
 }
 
diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index aada2ef96c62..041233b9b706 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -237,15 +237,15 @@ struct IO_APIC_route_entry __ioapic_read_entry(
 {
     union entry_union eu;
 
-    if ( raw )
+    if ( raw || !iommu_intremap )
     {
         eu.w1 = __io_apic_read(apic, 0x10 + 2 * pin);
         eu.w2 = __io_apic_read(apic, 0x11 + 2 * pin);
     }
     else
     {
-        eu.w1 = io_apic_read(apic, 0x10 + 2 * pin);
-        eu.w2 = io_apic_read(apic, 0x11 + 2 * pin);
+        eu.w1 = iommu_read_apic_from_ire(apic, 0x10 + 2 * pin);
+        eu.w2 = iommu_read_apic_from_ire(apic, 0x11 + 2 * pin);
     }
 
     return eu.entry;
@@ -269,15 +269,15 @@ void __ioapic_write_entry(
 {
     union entry_union eu = { .entry = e };
 
-    if ( raw )
+    if ( raw || !iommu_intremap )
     {
         __io_apic_write(apic, 0x11 + 2 * pin, eu.w2);
         __io_apic_write(apic, 0x10 + 2 * pin, eu.w1);
     }
     else
     {
-        io_apic_write(apic, 0x11 + 2 * pin, eu.w2);
-        io_apic_write(apic, 0x10 + 2 * pin, eu.w1);
+        iommu_update_ire_from_apic(apic, 0x11 + 2 * pin, eu.w2);
+        iommu_update_ire_from_apic(apic, 0x10 + 2 * pin, eu.w1);
     }
 }
 
@@ -433,16 +433,17 @@ static void modify_IO_APIC_irq(unsigned int irq, unsigned 
int enable,
                                unsigned int disable)
 {
     struct irq_pin_list *entry = irq_2_pin + irq;
-    unsigned int pin, reg;
 
     for (;;) {
-        pin = entry->pin;
+        unsigned int pin = entry->pin;
+        struct IO_APIC_route_entry rte;
+
         if (pin == -1)
             break;
-        reg = io_apic_read(entry->apic, 0x10 + pin*2);
-        reg &= ~disable;
-        reg |= enable;
-        io_apic_modify(entry->apic, 0x10 + pin*2, reg);
+        rte = __ioapic_read_entry(entry->apic, pin, false);
+        rte.raw &= ~(uint64_t)disable;
+        rte.raw |= enable;
+        __ioapic_write_entry(entry->apic, pin, false, rte);
         if (!entry->next)
             break;
         entry = irq_2_pin + entry->next;
@@ -584,16 +585,16 @@ set_ioapic_affinity_irq(struct irq_desc *desc, const 
cpumask_t *mask)
             dest = SET_APIC_LOGICAL_ID(dest);
         entry = irq_2_pin + irq;
         for (;;) {
-            unsigned int data;
+            struct IO_APIC_route_entry rte;
+
             pin = entry->pin;
             if (pin == -1)
                 break;
 
-            io_apic_write(entry->apic, 0x10 + 1 + pin*2, dest);
-            data = io_apic_read(entry->apic, 0x10 + pin*2);
-            data &= ~IO_APIC_REDIR_VECTOR_MASK;
-            data |= MASK_INSR(desc->arch.vector, IO_APIC_REDIR_VECTOR_MASK);
-            io_apic_modify(entry->apic, 0x10 + pin*2, data);
+            rte = __ioapic_read_entry(entry->apic, pin, false);
+            rte.dest.dest32 = dest;
+            rte.vector = desc->arch.vector;
+            __ioapic_write_entry(entry->apic, pin, false, rte);
 
             if (!entry->next)
                 break;
@@ -2127,10 +2128,8 @@ void ioapic_resume(void)
             reg_00.bits.ID = mp_ioapics[apic].mpc_apicid;
             __io_apic_write(apic, 0, reg_00.raw);
         }
-        for (i = 0; i < nr_ioapic_entries[apic]; i++, entry++) {
-            __io_apic_write(apic, 0x11+2*i, *(((int *)entry)+1));
-            __io_apic_write(apic, 0x10+2*i, *(((int *)entry)+0));
-        }
+        for (i = 0; i < nr_ioapic_entries[apic]; i++, entry++)
+            __ioapic_write_entry(apic, i, true, *entry);
     }
     spin_unlock_irqrestore(&ioapic_lock, flags);
 }
diff --git a/xen/drivers/passthrough/amd/iommu_intr.c 
b/xen/drivers/passthrough/amd/iommu_intr.c
index 9e6be3be3515..f32c418a7e49 100644
--- a/xen/drivers/passthrough/amd/iommu_intr.c
+++ b/xen/drivers/passthrough/amd/iommu_intr.c
@@ -361,12 +361,6 @@ void cf_check amd_iommu_ioapic_update_ire(
     struct amd_iommu *iommu;
     unsigned int idx;
 
-    if ( !iommu_intremap )
-    {
-        __io_apic_write(apic, reg, value);
-        return;
-    }
-
     idx = ioapic_id_to_index(IO_APIC_ID(apic));
     if ( idx == MAX_IO_APICS )
         return;
-- 
2.41.0