remove unnecessary loop for retrieving region

Signed-off-by: Thanos Makatos <thanos.makatos@nutanix.com>

4 files changed, 24 insertions, 27 deletions

diff --git a/lib/libmuser.c b/lib/libmuser.c
index 95d24a0..f9ce245 100644
--- a/lib/libmuser.c
+++ b/lib/libmuser.c
@@ -418,13 +418,20 @@ dev_get_sparse_mmap_cap(lm_ctx_t *lm_ctx, lm_reg_info_t *lm_reg,
 }
 
 #define LM_REGION_SHIFT 40
+#define LM_REGION_MASK  ((1ULL << LM_REGION_SHIFT) - 1)
 
 uint64_t
-region_offset(const uint32_t region)
+region_to_offset(const uint32_t region)
 {
     return (uint64_t)region << LM_REGION_SHIFT;
 }
 
+uint32_t
+offset_to_region(const uint64_t offset)
+{
+    return (offset >> LM_REGION_SHIFT) & LM_REGION_MASK;
+}
+
 static long
 dev_get_reginfo(lm_ctx_t * lm_ctx, struct vfio_region_info *vfio_reg)
 {
@@ -441,7 +448,7 @@ dev_get_reginfo(lm_ctx_t * lm_ctx, struct vfio_region_info *vfio_reg)
         return -EINVAL;
     }
 
-    vfio_reg->offset = region_offset(vfio_reg->index);
+    vfio_reg->offset = region_to_offset(vfio_reg->index);
     vfio_reg->flags = lm_reg->flags;
     vfio_reg->size = lm_reg->size;
 
@@ -573,7 +580,7 @@ static int muser_mmap(lm_ctx_t * lm_ctx, struct muser_cmd *cmd)
     unsigned long len = cmd->mmap.request.len;
     unsigned long pgoff = cmd->mmap.request.pgoff;
 
-    region = lm_get_region(lm_ctx, pgoff, len, &pgoff);
+    region = lm_get_region(pgoff, len, &pgoff);
     if (region < 0) {
         lm_log(lm_ctx, LM_ERR, "bad region %d\n", region);
         err = region;
@@ -630,26 +637,18 @@ post_read(lm_ctx_t * const lm_ctx, struct muser_cmd *const cmd, ssize_t ret)
 }
 
 int
-lm_get_region(lm_ctx_t * const lm_ctx, const loff_t pos, const size_t count,
-              loff_t * const off)
+lm_get_region(const loff_t pos, const size_t count, loff_t * const off)
 {
-    assert(lm_ctx);
-    assert(off);
-    lm_pci_info_t *pci_info = &lm_ctx->pci_info;
+    int r;
 
-    int i;
+    assert(off);
 
-    for (i = 0; i < LM_DEV_NUM_REGS; i++) {
-        const lm_reg_info_t * const reg_info = &pci_info->reg_info[i];
-        const uint64_t _region_offset = region_offset(i);
-        if (pos >= _region_offset) {
-            if (pos - _region_offset + count <= reg_info->size) {
-                *off = pos - _region_offset;
-                return i;
-            }
-        }
+    r = offset_to_region(pos);
+    if (offset_to_region(pos + count) != r) {
+        return -ENOENT; 
     }
-    return -ENOENT;
+    *off = pos - region_to_offset(r);
+    return r;
 }
 
 static ssize_t
@@ -689,7 +688,7 @@ do_access(lm_ctx_t * const lm_ctx, char * const buf, size_t count, loff_t pos,
     assert(count > 0);
 
     pci_info = &lm_ctx->pci_info;
-    idx = lm_get_region(lm_ctx, pos, count, &offset);
+    idx = lm_get_region(pos, count, &offset);
     if (idx < 0) {
         lm_log(lm_ctx, LM_ERR, "invalid region %d\n", idx);
         return idx;
diff --git a/lib/libmuser_pci.c b/lib/libmuser_pci.c
index 7131e94..488167d 100644
--- a/lib/libmuser_pci.c
+++ b/lib/libmuser_pci.c
@@ -275,7 +275,7 @@ muser_do_pci_hdr_access(lm_ctx_t * const lm_ctx, size_t * const count,
     assert(pos);
     assert(buf);
 
-    _pos = *pos - region_offset(LM_DEV_CFG_REG_IDX);
+    _pos = *pos - region_to_offset(LM_DEV_CFG_REG_IDX);
     _count = MIN(*count, PCI_STD_HEADER_SIZEOF - _pos);
 
     if (is_write) {
@@ -291,7 +291,7 @@ muser_do_pci_hdr_access(lm_ctx_t * const lm_ctx, size_t * const count,
 static inline bool
 muser_is_pci_hdr_access(const lm_reg_info_t * const reg_info, const loff_t pos)
 {
-    const off_t off = (loff_t) region_offset(LM_DEV_CFG_REG_IDX);
+    const off_t off = (loff_t) region_to_offset(LM_DEV_CFG_REG_IDX);
     return pos - off >= 0 && pos - off < PCI_STD_HEADER_SIZEOF;
 }
 
diff --git a/lib/muser.h b/lib/muser.h
index ac31a2e..0a3432a 100644
--- a/lib/muser.h
+++ b/lib/muser.h
@@ -402,16 +402,14 @@ lm_unmap_sg(lm_ctx_t * const lm_ctx, const dma_sg_t * sg,
  * Returns the PCI region given the position and size of an address span in the
  * PCI configuration space.
  *
- * @lm_ctx: the libmuser context
  * @pos: offset of the address span
  * @count: size of the address span
  * @off: output parameter that receives the relative offset within the region.
  *
- * Returns the PCI region (LM_DEV_XXX_REG_IDX), or -1 on error. Sets errno.
+ * Returns the PCI region (LM_DEV_XXX_REG_IDX), or -errno on error.
  */
 int
-lm_get_region(lm_ctx_t * const lm_ctx, const loff_t pos,
-              const size_t count, loff_t * const off);
+lm_get_region(const loff_t pos, const size_t count, loff_t * const off);
 
 /*
  * Advanced stuff.
diff --git a/lib/muser_priv.h b/lib/muser_priv.h
index 4df8b25..e5af663 100644
--- a/lib/muser_priv.h
+++ b/lib/muser_priv.h
@@ -7,5 +7,5 @@ muser_pci_hdr_access(lm_ctx_t * const lm_ctx, size_t * const count,
 
 lm_reg_info_t *lm_get_region_info(lm_ctx_t * const lm_ctx);
 
-uint64_t region_offset(const uint32_t region);
+uint64_t region_to_offset(const uint32_t region);