spapr_pci: Fix number of returned vectors in ibm, change-msi

Current guest kernels try allocating as many vectors as the quota is.
For example, in the case of virtio-net (which has just 3 vectors)
the guest requests 4 vectors (that is the quota in the test) and
the existing ibm,change-msi handler returns 4. But before it returns,
it calls msix_set_message() in a loop and corrupts memory behind
the end of msix_table.

This limits the number of vectors returned by ibm,change-msi to
the maximum supported by the actual device.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: qemu-stable@nongnu.org
[agraf: squash in bugfix from aik]
Signed-off-by: Alexander Graf <agraf@suse.de>
(cherry picked from commit b26696b519f853c9844e5154858e583600ee3cdc)

*s/error_report/fprintf/ to reflect v1.7.x error reporting style

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index edb4cb0413..0079d31195 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -342,6 +342,22 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, sPAPREnvironment *spapr,
 
     /* There is no cached config, allocate MSIs */
     if (!phb->msi_table[ndev].nvec) {
+        int max_irqs = 0;
+        if (ret_intr_type == RTAS_TYPE_MSI) {
+            max_irqs = msi_nr_vectors_allocated(pdev);
+        } else if (ret_intr_type == RTAS_TYPE_MSIX) {
+            max_irqs = pdev->msix_entries_nr;
+        }
+        if (!max_irqs) {
+            fprintf(stderr,
+                    "Requested interrupt type %d is not enabled for device#%d\n",
+                    ret_intr_type, ndev);
+            rtas_st(rets, 0, -1); /* Hardware error */
+            return;
+        }
+        if (req_num > max_irqs) {
+            req_num = max_irqs;
+        }
         irq = spapr_allocate_irq_block(req_num, false,
                                        ret_intr_type == RTAS_TYPE_MSI);
         if (irq < 0) {