[Xen-devel] [PATCH 3/9] AMD/IOMMU: use bit field for IRTE

["Jan Beulich" <JBeulich@suse.com>]

At the same time restrict its scope to just the single source file
actually using it, and abstract accesses by introducing a union of
pointers. (A union of the actual table entries is not used to make it
impossible to [wrongly, once the 128-bit form gets added] perform
pointer arithmetic / array accesses on derived types.)

Also move away from updating the entries piecemeal: Construct a full new
entry, and write it out.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
It would have been nice to use write_atomic() or ACCESS_ONCE() for the
actual writes, but both cast the value to a scalar one, which doesn't
suit us here (and I also didn't want to make the compound type a union
with a raw member just for this).

--- a/xen/drivers/passthrough/amd/iommu_intr.c
+++ b/xen/drivers/passthrough/amd/iommu_intr.c
@@ -23,6 +23,23 @@
 #include <asm/io_apic.h>
 #include <xen/keyhandler.h>
 
+struct irte_basic {
+    unsigned int remap_en:1;
+    unsigned int sup_io_pf:1;
+    unsigned int int_type:3;
+    unsigned int rq_eoi:1;
+    unsigned int dm:1;
+    unsigned int guest_mode:1; /* MBZ */
+    unsigned int dest:8;
+    unsigned int vector:8;
+    unsigned int :8;
+};
+
+union irte_ptr {
+    void *raw;
+    struct irte_basic *basic;
+};
+
 #define INTREMAP_TABLE_ORDER    1
 #define INTREMAP_LENGTH 0xB
 #define INTREMAP_ENTRIES (1 << INTREMAP_LENGTH)
@@ -101,47 +118,44 @@ static unsigned int alloc_intremap_entry
     return slot;
 }
 
-static u32 *get_intremap_entry(int seg, int bdf, int offset)
+static union irte_ptr get_intremap_entry(unsigned int seg, unsigned int bdf,
+                                         unsigned int offset)
 {
-    u32 *table = get_ivrs_mappings(seg)[bdf].intremap_table;
+    union irte_ptr table = {
+        .raw = get_ivrs_mappings(seg)[bdf].intremap_table
+    };
+
+    ASSERT(table.raw && (offset < INTREMAP_ENTRIES));
 
-    ASSERT( (table != NULL) && (offset < INTREMAP_ENTRIES) );
+    table.basic += offset;
 
-    return table + offset;
+    return table;
 }
 
-static void free_intremap_entry(int seg, int bdf, int offset)
+static void free_intremap_entry(unsigned int seg, unsigned int bdf, unsigned int offset)
 {
-    u32 *entry = get_intremap_entry(seg, bdf, offset);
+    union irte_ptr entry = get_intremap_entry(seg, bdf, offset);
+
+    *entry.basic = (struct irte_basic){};
 
-    memset(entry, 0, sizeof(u32));
     __clear_bit(offset, get_ivrs_mappings(seg)[bdf].intremap_inuse);
 }
 
-static void update_intremap_entry(u32* entry, u8 vector, u8 int_type,
-    u8 dest_mode, u8 dest)
-{
-    set_field_in_reg_u32(IOMMU_CONTROL_ENABLED, 0,
-                            INT_REMAP_ENTRY_REMAPEN_MASK,
-                            INT_REMAP_ENTRY_REMAPEN_SHIFT, entry);
-    set_field_in_reg_u32(IOMMU_CONTROL_DISABLED, *entry,
-                            INT_REMAP_ENTRY_SUPIOPF_MASK,
-                            INT_REMAP_ENTRY_SUPIOPF_SHIFT, entry);
-    set_field_in_reg_u32(int_type, *entry,
-                            INT_REMAP_ENTRY_INTTYPE_MASK,
-                            INT_REMAP_ENTRY_INTTYPE_SHIFT, entry);
-    set_field_in_reg_u32(IOMMU_CONTROL_DISABLED, *entry,
-                            INT_REMAP_ENTRY_REQEOI_MASK,
-                            INT_REMAP_ENTRY_REQEOI_SHIFT, entry);
-    set_field_in_reg_u32((u32)dest_mode, *entry,
-                            INT_REMAP_ENTRY_DM_MASK,
-                            INT_REMAP_ENTRY_DM_SHIFT, entry);
-    set_field_in_reg_u32((u32)dest, *entry,
-                            INT_REMAP_ENTRY_DEST_MAST,
-                            INT_REMAP_ENTRY_DEST_SHIFT, entry);
-    set_field_in_reg_u32((u32)vector, *entry,
-                            INT_REMAP_ENTRY_VECTOR_MASK,
-                            INT_REMAP_ENTRY_VECTOR_SHIFT, entry);
+static void update_intremap_entry(union irte_ptr entry, unsigned int vector,
+                                  unsigned int int_type,
+                                  unsigned int dest_mode, unsigned int dest)
+{
+    struct irte_basic basic = {
+        .remap_en = 1,
+        .sup_io_pf = 0,
+        .int_type = int_type,
+        .rq_eoi = 0,
+        .dm = dest_mode,
+        .dest = dest,
+        .vector = vector,
+    };
+
+    *entry.basic = basic;
 }
 
 static inline int get_rte_index(const struct IO_APIC_route_entry *rte)
@@ -163,7 +177,7 @@ static int update_intremap_entry_from_io
     u16 *index)
 {
     unsigned long flags;
-    u32* entry;
+    union irte_ptr entry;
     u8 delivery_mode, dest, vector, dest_mode;
     int req_id;
     spinlock_t *lock;
@@ -201,12 +215,8 @@ static int update_intremap_entry_from_io
          * so need to recover vector and delivery mode from IRTE.
          */
         ASSERT(get_rte_index(rte) == offset);
-        vector = get_field_from_reg_u32(*entry,
-                                        INT_REMAP_ENTRY_VECTOR_MASK,
-                                        INT_REMAP_ENTRY_VECTOR_SHIFT);
-        delivery_mode = get_field_from_reg_u32(*entry,
-                                               INT_REMAP_ENTRY_INTTYPE_MASK,
-                                               INT_REMAP_ENTRY_INTTYPE_SHIFT);
+        vector = entry.basic->vector;
+        delivery_mode = entry.basic->int_type;
     }
     update_intremap_entry(entry, vector, delivery_mode, dest_mode, dest);
 
@@ -228,7 +238,7 @@ int __init amd_iommu_setup_ioapic_remapp
 {
     struct IO_APIC_route_entry rte;
     unsigned long flags;
-    u32* entry;
+    union irte_ptr entry;
     int apic, pin;
     u8 delivery_mode, dest, vector, dest_mode;
     u16 seg, bdf, req_id;
@@ -407,16 +417,12 @@ unsigned int amd_iommu_read_ioapic_from_
         u16 bdf = ioapic_sbdf[idx].bdf;
         u16 seg = ioapic_sbdf[idx].seg;
         u16 req_id = get_intremap_requestor_id(seg, bdf);
-        const u32 *entry = get_intremap_entry(seg, req_id, offset);
+        union irte_ptr entry = get_intremap_entry(seg, req_id, offset);
 
         ASSERT(offset == (val & (INTREMAP_ENTRIES - 1)));
         val &= ~(INTREMAP_ENTRIES - 1);
-        val |= get_field_from_reg_u32(*entry,
-                                      INT_REMAP_ENTRY_INTTYPE_MASK,
-                                      INT_REMAP_ENTRY_INTTYPE_SHIFT) << 8;
-        val |= get_field_from_reg_u32(*entry,
-                                      INT_REMAP_ENTRY_VECTOR_MASK,
-                                      INT_REMAP_ENTRY_VECTOR_SHIFT);
+        val |= MASK_INSR(entry.basic->int_type, IO_APIC_REDIR_DELIV_MODE_MASK);
+        val |= MASK_INSR(entry.basic->vector, IO_APIC_REDIR_VECTOR_MASK);
     }
 
     return val;
@@ -427,7 +433,7 @@ static int update_intremap_entry_from_ms
     int *remap_index, const struct msi_msg *msg, u32 *data)
 {
     unsigned long flags;
-    u32* entry;
+    union irte_ptr entry;
     u16 req_id, alias_id;
     u8 delivery_mode, dest, vector, dest_mode;
     spinlock_t *lock;
@@ -581,7 +587,7 @@ void amd_iommu_read_msi_from_ire(
     const struct pci_dev *pdev = msi_desc->dev;
     u16 bdf = pdev ? PCI_BDF2(pdev->bus, pdev->devfn) : hpet_sbdf.bdf;
     u16 seg = pdev ? pdev->seg : hpet_sbdf.seg;
-    const u32 *entry;
+    union irte_ptr entry;
 
     if ( IS_ERR_OR_NULL(_find_iommu_for_device(seg, bdf)) )
         return;
@@ -597,12 +603,8 @@ void amd_iommu_read_msi_from_ire(
     }
 
     msg->data &= ~(INTREMAP_ENTRIES - 1);
-    msg->data |= get_field_from_reg_u32(*entry,
-                                        INT_REMAP_ENTRY_INTTYPE_MASK,
-                                        INT_REMAP_ENTRY_INTTYPE_SHIFT) << 8;
-    msg->data |= get_field_from_reg_u32(*entry,
-                                        INT_REMAP_ENTRY_VECTOR_MASK,
-                                        INT_REMAP_ENTRY_VECTOR_SHIFT);
+    msg->data |= MASK_INSR(entry.basic->int_type, MSI_DATA_DELIVERY_MODE_MASK);
+    msg->data |= MASK_INSR(entry.basic->vector, MSI_DATA_VECTOR_MASK);
 }
 
 int __init amd_iommu_free_intremap_table(
--- a/xen/include/asm-x86/hvm/svm/amd-iommu-defs.h
+++ b/xen/include/asm-x86/hvm/svm/amd-iommu-defs.h
@@ -468,22 +468,6 @@ struct amd_iommu_pte {
 #define IOMMU_CONTROL_DISABLED	0
 #define IOMMU_CONTROL_ENABLED	1
 
-/* interrupt remapping table */
-#define INT_REMAP_ENTRY_REMAPEN_MASK    0x00000001
-#define INT_REMAP_ENTRY_REMAPEN_SHIFT   0
-#define INT_REMAP_ENTRY_SUPIOPF_MASK    0x00000002
-#define INT_REMAP_ENTRY_SUPIOPF_SHIFT   1
-#define INT_REMAP_ENTRY_INTTYPE_MASK    0x0000001C
-#define INT_REMAP_ENTRY_INTTYPE_SHIFT   2
-#define INT_REMAP_ENTRY_REQEOI_MASK     0x00000020
-#define INT_REMAP_ENTRY_REQEOI_SHIFT    5
-#define INT_REMAP_ENTRY_DM_MASK         0x00000040
-#define INT_REMAP_ENTRY_DM_SHIFT        6
-#define INT_REMAP_ENTRY_DEST_MAST       0x0000FF00
-#define INT_REMAP_ENTRY_DEST_SHIFT      8
-#define INT_REMAP_ENTRY_VECTOR_MASK     0x00FF0000
-#define INT_REMAP_ENTRY_VECTOR_SHIFT    16
-
 #define INV_IOMMU_ALL_PAGES_ADDRESS      ((1ULL << 63) - 1)
 
 #define IOMMU_RING_BUFFER_PTR_MASK                  0x0007FFF0




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