[xen staging] vpci: Refactor vpci_remove_register to remove matched registers

[patchbot@xxxxxxx]

commit 862331815722bbbc7cf4750f5adb45ae0be29220
Author:     Jiqian Chen <Jiqian.Chen@xxxxxxx>
AuthorDate: Mon Sep 1 11:13:22 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 1 13:07:01 2025 +0200

    vpci: Refactor vpci_remove_register to remove matched registers
    
    vpci_remove_register() only supports removing a register in a time,
    but the follow-on changes need to remove all registers within a range.
    So, refactor it to support removing all registers in a given region.
    
    And it is no issue to remove a non exist register, so remove the
    __must_check prefix.
    
    Note: two test cases don't math the new logic of
    vpci_remove_registers(), then modify them.
    
    Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 tools/tests/vpci/main.c |  8 ++++----
 xen/drivers/vpci/vpci.c | 38 ++++++++++++++++++++------------------
 xen/include/xen/vpci.h  |  4 ++--
 3 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/tools/tests/vpci/main.c b/tools/tests/vpci/main.c
index 33223db3eb..2ef8d4e03f 100644
--- a/tools/tests/vpci/main.c
+++ b/tools/tests/vpci/main.c
@@ -132,10 +132,10 @@ static void vpci_write32_mask(const struct pci_dev *pdev, 
unsigned int reg,
                                   rsvdz_mask))
 
 #define VPCI_REMOVE_REG(off, size)                                          \
-    assert(!vpci_remove_register(test_pdev.vpci, off, size))
+    assert(!vpci_remove_registers(test_pdev.vpci, off, size))
 
 #define VPCI_REMOVE_INVALID_REG(off, size)                                  \
-    assert(vpci_remove_register(test_pdev.vpci, off, size))
+    assert(vpci_remove_registers(test_pdev.vpci, off, size))
 
 /* Read a 32b register using all possible sizes. */
 void multiread4_check(unsigned int reg, uint32_t val)
@@ -402,10 +402,10 @@ main(int argc, char **argv)
     VPCI_REMOVE_REG(28, 1);
     VPCI_REMOVE_REG(24, 4);
     VPCI_REMOVE_REG(12, 2);
+    VPCI_REMOVE_REG(16, 2);
+    VPCI_REMOVE_REG(30, 2);
 
     VPCI_REMOVE_INVALID_REG(20, 1);
-    VPCI_REMOVE_INVALID_REG(16, 2);
-    VPCI_REMOVE_INVALID_REG(30, 2);
 
     return 0;
 }
diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 36a288ddf4..07c7071d0a 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -152,7 +152,7 @@ static int vpci_capability_hide(const struct pci_dev *pdev, 
unsigned int cap)
 
     prev_r->private = next_r->private;
     /*
-     * Not calling vpci_remove_register() here is to avoid redoing
+     * Not calling vpci_remove_registers() here is to avoid redoing
      * the register search.
      */
     list_del(&next_r->node);
@@ -160,7 +160,7 @@ static int vpci_capability_hide(const struct pci_dev *pdev, 
unsigned int cap)
     xfree(next_r);
 
     if ( !is_hardware_domain(pdev->domain) )
-        return vpci_remove_register(vpci, offset + PCI_CAP_LIST_ID, 1);
+        return vpci_remove_registers(vpci, offset + PCI_CAP_LIST_ID, 1);
 
     return 0;
 }
@@ -573,34 +573,36 @@ int vpci_add_register_mask(struct vpci *vpci, vpci_read_t 
*read_handler,
     return 0;
 }
 
-int vpci_remove_register(struct vpci *vpci, unsigned int offset,
-                         unsigned int size)
+int vpci_remove_registers(struct vpci *vpci, unsigned int start,
+                          unsigned int size)
 {
-    const struct vpci_register r = { .offset = offset, .size = size };
-    struct vpci_register *rm;
+    struct vpci_register *rm, *tmp;
+    unsigned int end = start + size;
 
     spin_lock(&vpci->lock);
-    list_for_each_entry ( rm, &vpci->handlers, node )
+    list_for_each_entry_safe ( rm, tmp, &vpci->handlers, node )
     {
-        int cmp = vpci_register_cmp(&r, rm);
-
-        /*
-         * NB: do not use a switch so that we can use break to
-         * get out of the list loop earlier if required.
-         */
-        if ( !cmp && rm->offset == offset && rm->size == size )
+        /* Remove rm if rm is inside the range. */
+        if ( rm->offset >= start && rm->offset + rm->size <= end )
         {
             list_del(&rm->node);
-            spin_unlock(&vpci->lock);
             xfree(rm);
-            return 0;
+            continue;
         }
-        if ( cmp <= 0 )
+
+        /* Return error if registers overlap but not inside. */
+        if ( rm->offset + rm->size > start && rm->offset < end )
+        {
+            spin_unlock(&vpci->lock);
+            return -ERANGE;
+        }
+
+        if ( start < rm->offset )
             break;
     }
     spin_unlock(&vpci->lock);
 
-    return -ENOENT;
+    return 0;
 }
 
 /* Wrappers for performing reads/writes to the underlying hardware. */
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index 4b7b9298c4..9ae75d946a 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -70,8 +70,8 @@ static inline int __must_check vpci_add_register(struct vpci 
*vpci,
                                   size, data, 0, 0, 0, 0);
 }
 
-int __must_check vpci_remove_register(struct vpci *vpci, unsigned int offset,
-                                      unsigned int size);
+int vpci_remove_registers(struct vpci *vpci, unsigned int start,
+                          unsigned int size);
 
 /* Generic read/write handlers for the PCI config space. */
 uint32_t vpci_read(pci_sbdf_t sbdf, unsigned int reg, unsigned int size);
--
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