[PATCH] x86/msi: fix locking for SRIOV devices

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

In commit 4f78438b45e2 ("vpci: use per-domain PCI lock to protect vpci
structure") a lock moved from allocate_and_map_msi_pirq() to the caller
and changed from pcidevs_lock() to read_lock(&d->pci_lock). However, one
call path wasn't updated to reflect the change, leading to a failed
assertion observed on debug builds of Xen when an SRIOV device is
present with one or more VFs enabled:

(XEN) Assertion 'd || pcidevs_locked()' failed at drivers/passthrough/pci.c:535
(XEN) ----[ Xen-4.20-unstable  x86_64  debug=y  Not tainted ]----
...
(XEN) Xen call trace:
(XEN)    [<ffff82d040284da8>] R pci_get_pdev+0x4c/0xab
(XEN)    [<ffff82d040344f5c>] F arch/x86/msi.c#read_pci_mem_bar+0x58/0x272
(XEN)    [<ffff82d04034530e>] F arch/x86/msi.c#msix_capability_init+0x198/0x755
(XEN)    [<ffff82d040345dad>] F arch/x86/msi.c#__pci_enable_msix+0x82/0xe8
(XEN)    [<ffff82d0403463e5>] F pci_enable_msi+0x3f/0x78
(XEN)    [<ffff82d04034be2b>] F map_domain_pirq+0x2a4/0x6dc
(XEN)    [<ffff82d04034d4d5>] F allocate_and_map_msi_pirq+0x103/0x262
(XEN)    [<ffff82d04035da5d>] F physdev_map_pirq+0x210/0x259
(XEN)    [<ffff82d04035e798>] F do_physdev_op+0x9c3/0x1454
(XEN)    [<ffff82d040329475>] F pv_hypercall+0x5ac/0x6af
(XEN)    [<ffff82d0402012d3>] F lstar_enter+0x143/0x150

Fix it by passing the struct domain pointer to pci_get_pdev() in this
call path.

Fixes: 4f78438b45e2 ("vpci: use per-domain PCI lock to protect vpci structure")
Reported-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
Candidate for backport to 4.19
---
 xen/arch/x86/msi.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index 0c97fbb3fc03..95a48615a1a4 100644
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -662,7 +662,8 @@ static int msi_capability_init(struct pci_dev *dev,
     return 0;
 }
 
-static u64 read_pci_mem_bar(u16 seg, u8 bus, u8 slot, u8 func, u8 bir, int vf)
+static u64 read_pci_mem_bar(struct domain *d, u16 seg, u8 bus, u8 slot, u8 
func,
+                            u8 bir, int vf)
 {
     u8 limit;
     u32 addr, base = PCI_BASE_ADDRESS_0;
@@ -670,8 +671,7 @@ static u64 read_pci_mem_bar(u16 seg, u8 bus, u8 slot, u8 
func, u8 bir, int vf)
 
     if ( vf >= 0 )
     {
-        struct pci_dev *pdev = pci_get_pdev(NULL,
-                                            PCI_SBDF(seg, bus, slot, func));
+        struct pci_dev *pdev = pci_get_pdev(d, PCI_SBDF(seg, bus, slot, func));
         unsigned int pos;
         uint16_t ctrl, num_vf, offset, stride;
 
@@ -829,7 +829,8 @@ static int msix_capability_init(struct pci_dev *dev,
             vf = dev->sbdf.bdf;
         }
 
-        table_paddr = read_pci_mem_bar(seg, pbus, pslot, pfunc, bir, vf);
+        table_paddr = read_pci_mem_bar(dev->domain, seg, pbus, pslot, pfunc,
+                                       bir, vf);
         WARN_ON(msi && msi->table_base != table_paddr);
         if ( !table_paddr )
         {
@@ -852,7 +853,8 @@ static int msix_capability_init(struct pci_dev *dev,
 
         pba_offset = pci_conf_read32(dev->sbdf, msix_pba_offset_reg(pos));
         bir = (u8)(pba_offset & PCI_MSIX_BIRMASK);
-        pba_paddr = read_pci_mem_bar(seg, pbus, pslot, pfunc, bir, vf);
+        pba_paddr = read_pci_mem_bar(dev->domain, seg, pbus, pslot, pfunc, bir,
+                                     vf);
         WARN_ON(!pba_paddr);
         pba_paddr += pba_offset & ~PCI_MSIX_BIRMASK;
 
-- 
2.46.0