[xen staging] vPCI/ReBAR: improve cleanup

[patchbot@xxxxxxx]

commit 9ebba62ca8430604b0bf77f05925b40eee2504db
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Mar 5 09:27:08 2026 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 5 09:27:08 2026 +0100

    vPCI/ReBAR: improve cleanup
    
    We cannot assume extended config space to (still) be accessible when
    cleaning up. Necessary values need caching instead. In fact, as the caller
    also cannot look up extended capabilities, the cleanup function needs to
    cope with being called when there's no ReBAR capability at all.
    
    As kind of a side effect nbars being 0 (which init_rebar() doesn't
    explicitly reject) no longer results in a bogus call to
    vpci_remove_registers().
    
    Fixes: ee459aeac096 ("vpci/rebar: Implement cleanup function for Rebar")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/drivers/vpci/rebar.c | 15 +++++++--------
 xen/include/xen/vpci.h   |  7 +++++++
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/xen/drivers/vpci/rebar.c b/xen/drivers/vpci/rebar.c
index ab5c5453a8..1bb3dd7045 100644
--- a/xen/drivers/vpci/rebar.c
+++ b/xen/drivers/vpci/rebar.c
@@ -53,17 +53,12 @@ static void cf_check rebar_ctrl_write(const struct pci_dev 
*pdev,
 static int cf_check cleanup_rebar(const struct pci_dev *pdev, bool hide)
 {
     int rc;
-    uint32_t ctrl;
-    unsigned int nbars;
-    unsigned int rebar_offset = pci_find_ext_capability(pdev,
-                                                        PCI_EXT_CAP_ID_REBAR);
+    unsigned int nbars = pdev->vpci->rebar.nbars;
+    unsigned int rebar_offset = pdev->vpci->rebar.offset;
 
-    if ( !hide )
+    if ( !rebar_offset || !nbars || !hide )
         return 0;
 
-    ctrl = pci_conf_read32(pdev->sbdf, rebar_offset + PCI_REBAR_CTRL(0));
-    nbars = MASK_EXTR(ctrl, PCI_REBAR_CTRL_NBAR_MASK);
-
     rc = vpci_remove_registers(pdev->vpci, rebar_offset + PCI_REBAR_CAP(0),
                                PCI_REBAR_CTRL(nbars - 1));
     if ( rc )
@@ -121,6 +116,10 @@ static int cf_check init_rebar(struct pci_dev *pdev)
 
     ctrl = pci_conf_read32(pdev->sbdf, rebar_offset + PCI_REBAR_CTRL(0));
     nbars = MASK_EXTR(ctrl, PCI_REBAR_CTRL_NBAR_MASK);
+
+    pdev->vpci->rebar.offset = rebar_offset;
+    pdev->vpci->rebar.nbars  = nbars;
+
     for ( unsigned int i = 0; i < nbars; i++ )
     {
         int rc;
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index d104efbce2..83ac41edf8 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -135,6 +135,13 @@ struct vpci {
             struct vpci_arch_msix_entry arch;
         } entries[];
     } *msix;
+
+    /* Resizable BARs data */
+    struct vpci_rebar {
+        unsigned int offset:12;
+        unsigned int nbars:3;
+    } rebar;
+
 #ifdef CONFIG_HAS_VPCI_GUEST_SUPPORT
     /* Guest SBDF of the device. */
 #define INVALID_GUEST_SBDF ((pci_sbdf_t){ .sbdf = ~0U })
--
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