diff --git a/xen/drivers/vpci/Makefile b/xen/drivers/vpci/Makefile
index 1a1413b93e76..a7c8a30a8956 100644
--- a/xen/drivers/vpci/Makefile
+++ b/xen/drivers/vpci/Makefile
@@ -1,2 +1,2 @@
-obj-y += vpci.o header.o
+obj-y += vpci.o header.o rebar.o
 obj-$(CONFIG_HAS_PCI_MSI) += msi.o msix.o
diff --git a/xen/drivers/vpci/rebar.c b/xen/drivers/vpci/rebar.c
new file mode 100644
index 000000000000..8c611cf0cd91
--- /dev/null
+++ b/xen/drivers/vpci/rebar.c
@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2025 Advanced Micro Devices, Inc. All Rights Reserved.
+ *
+ * Author: Jiqian Chen <Jiqian.Chen@amd.com>
+ */
+
+#include <xen/sched.h>
+#include <xen/vpci.h>
+
+static void cf_check rebar_ctrl_write(const struct pci_dev *pdev,
+                                      unsigned int reg,
+                                      uint32_t val,
+                                      void *data)
+{
+    struct vpci_bar *bar = data;
+    const unsigned int index = bar - pdev->vpci->header.bars;
+    uint64_t size = PCI_REBAR_CTRL_SIZE(val);
+
+    if ( bar->enabled )
+    {
+        /*
+         * Refuse to resize a BAR while memory decoding is enabled, as
+         * otherwise the size of the mapped region in the p2m would become
+         * stale with the newly set BAR size, and the position of the BAR
+         * would be reset to undefined.  Note the PCIe specification also
+         * forbids resizing a BAR with memory decoding enabled.
+         */
+        if ( size != bar->size )
+            gprintk(XENLOG_ERR,
+                    "%pp: refuse to resize BAR#%u with memory decoding enabled\n",
+                    &pdev->sbdf, index);
+        return;
+    }
+
+    if ( !((size >> PCI_REBAR_CTRL_SIZE_BIAS) & bar->resizable_sizes) )
+        gprintk(XENLOG_WARNING,
+                "%pp: new BAR#%u size %#lx is not supported by hardware\n",
+                &pdev->sbdf, index, size);
+
+    pci_conf_write32(pdev->sbdf, reg, val);
+
+    pci_size_mem_bar(pdev->sbdf,
+                     PCI_BASE_ADDRESS_0 + index * 4,
+                     &bar->addr,
+                     &bar->size,
+                     (index == PCI_HEADER_NORMAL_NR_BARS - 1) ?
+                      PCI_BAR_LAST : 0);
+    bar->guest_addr = bar->addr;
+}
+
+static int cf_check init_rebar(struct pci_dev *pdev)
+{
+    uint32_t ctrl;
+    unsigned int nbars;
+    unsigned int rebar_offset = pci_find_ext_capability(pdev->sbdf,
+                                                        PCI_EXT_CAP_ID_REBAR);
+
+    if ( !rebar_offset )
+        return 0;
+
+    if ( !is_hardware_domain(pdev->domain) )
+    {
+        printk(XENLOG_ERR "%pp: resizable BARs unsupported for unpriv %pd\n",
+               &pdev->sbdf, pdev->domain);
+        return -EOPNOTSUPP;
+    }
+
+    ctrl = pci_conf_read32(pdev->sbdf, rebar_offset + PCI_REBAR_CTRL(0));
+    nbars = MASK_EXTR(ctrl, PCI_REBAR_CTRL_NBAR_MASK);
+    for ( unsigned int i = 0; i < nbars; i++ )
+    {
+        int rc;
+        struct vpci_bar *bar;
+        unsigned int index;
+
+        ctrl = pci_conf_read32(pdev->sbdf, rebar_offset + PCI_REBAR_CTRL(i));
+        index = ctrl & PCI_REBAR_CTRL_BAR_IDX;
+        if ( index >= PCI_HEADER_NORMAL_NR_BARS )
+        {
+            printk(XENLOG_ERR "%pd %pp: too big BAR number %u in REBAR_CTRL\n",
+                   pdev->domain, &pdev->sbdf, index);
+            continue;
+        }
+
+        bar = &pdev->vpci->header.bars[index];
+        if ( bar->type != VPCI_BAR_MEM64_LO && bar->type != VPCI_BAR_MEM32 )
+        {
+            printk(XENLOG_ERR "%pd %pp: BAR%u is not in memory space\n",
+                   pdev->domain, &pdev->sbdf, index);
+            continue;
+        }
+
+        rc = vpci_add_register(pdev->vpci, vpci_hw_read32, vpci_hw_write32,
+                               rebar_offset + PCI_REBAR_CAP(i), 4, NULL);
+        if ( rc )
+        {
+            /*
+             * TODO: for failed pathes, need to hide ReBar capability
+             * from hardware domain instead of returning an error.
+             */
+            printk(XENLOG_ERR "%pd %pp: BAR%u fail to add reg of REBAR_CAP rc=%d\n",
+                   pdev->domain, &pdev->sbdf, index, rc);
+            continue;
+        }
+
+        rc = vpci_add_register(pdev->vpci, vpci_hw_read32, rebar_ctrl_write,
+                               rebar_offset + PCI_REBAR_CTRL(i), 4, bar);
+        if ( rc )
+        {
+            printk(XENLOG_ERR "%pd %pp: BAR%u fail to add reg of REBAR_CTRL rc=%d\n",
+                   pdev->domain, &pdev->sbdf, index, rc);
+            continue;
+        }
+
+        bar->resizable_sizes =
+            MASK_EXTR(pci_conf_read32(pdev->sbdf,
+                                      rebar_offset + PCI_REBAR_CAP(i)),
+                      PCI_REBAR_CAP_SIZES_MASK);
+        bar->resizable_sizes |=
+            (((uint64_t)MASK_EXTR(ctrl, PCI_REBAR_CTRL_SIZES_MASK) << 32) /
+             ISOLATE_LSB(PCI_REBAR_CAP_SIZES_MASK));
+    }
+
+    return 0;
+}
+REGISTER_VPCI_INIT(init_rebar, VPCI_PRIORITY_LOW);
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 1e6aa5d799b9..3349b98389b8 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -232,6 +232,12 @@ void cf_check vpci_hw_write16(
     pci_conf_write16(pdev->sbdf, reg, val);
 }
 
+void cf_check vpci_hw_write32(
+    const struct pci_dev *pdev, unsigned int reg, uint32_t val, void *data)
+{
+    pci_conf_write32(pdev->sbdf, reg, val);
+}
+
 int vpci_add_register_mask(struct vpci *vpci, vpci_read_t *read_handler,
                            vpci_write_t *write_handler, unsigned int offset,
                            unsigned int size, void *data, uint32_t ro_mask,
diff --git a/xen/include/xen/pci_regs.h b/xen/include/xen/pci_regs.h
index 250ba106dbd3..2f1d0d63e962 100644
--- a/xen/include/xen/pci_regs.h
+++ b/xen/include/xen/pci_regs.h
@@ -459,6 +459,7 @@
 #define PCI_EXT_CAP_ID_ARI	14
 #define PCI_EXT_CAP_ID_ATS	15
 #define PCI_EXT_CAP_ID_SRIOV	16
+#define PCI_EXT_CAP_ID_REBAR	21	/* Resizable BAR */
 
 /* Advanced Error Reporting */
 #define PCI_ERR_UNCOR_STATUS	4	/* Uncorrectable Error Status */
@@ -541,6 +542,20 @@
 #define  PCI_VNDR_HEADER_REV(x)	(((x) >> 16) & 0xf)
 #define  PCI_VNDR_HEADER_LEN(x)	(((x) >> 20) & 0xfff)
 
+/* Resizable BARs */
+#define PCI_REBAR_CAP(n)	(4 + 8 * (n))	/* capability register */
+#define  PCI_REBAR_CAP_SIZES_MASK	0xFFFFFFF0U	/* supported BAR sizes in CAP */
+#define PCI_REBAR_CTRL(n)	(8 + 8 * (n))	/* control register */
+#define  PCI_REBAR_CTRL_BAR_IDX		0x00000007	/* BAR index */
+#define  PCI_REBAR_CTRL_NBAR_MASK	0x000000E0	/* # of resizable BARs */
+#define  PCI_REBAR_CTRL_BAR_SIZE	0x00003F00	/* BAR size */
+#define  PCI_REBAR_CTRL_SIZES_MASK	0xFFFF0000U	/* supported BAR sizes in CTRL */
+
+#define PCI_REBAR_CTRL_SIZE_BIAS	20
+#define PCI_REBAR_CTRL_SIZE(v) \
+            (1ULL << (MASK_EXTR(v, PCI_REBAR_CTRL_BAR_SIZE) \
+                      + PCI_REBAR_CTRL_SIZE_BIAS))
+
 /*
  * Hypertransport sub capability types
  *
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index 41e7c3bc2791..9d47b8c1a50e 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -78,6 +78,8 @@ uint32_t cf_check vpci_hw_read32(
     const struct pci_dev *pdev, unsigned int reg, void *data);
 void cf_check vpci_hw_write16(
     const struct pci_dev *pdev, unsigned int reg, uint32_t val, void *data);
+void cf_check vpci_hw_write32(
+    const struct pci_dev *pdev, unsigned int reg, uint32_t val, void *data);
 
 /*
  * Check for pending vPCI operations on this vcpu. Returns true if the vcpu
@@ -100,6 +102,7 @@ struct vpci {
             /* Guest address. */
             uint64_t guest_addr;
             uint64_t size;
+            uint64_t resizable_sizes;
             struct rangeset *mem;
             enum {
                 VPCI_BAR_EMPTY,
