Re: [PATCH v5 11/21] KVM: s390: pci: do initial setup for AEN interpretation

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On 4/14/22 3:20 AM, Christian Borntraeger wrote:


Am 04.04.22 um 19:43 schrieb Matthew Rosato:
Initial setup for Adapter Event Notification Interpretation for zPCI
passthrough devices.  Specifically, allocate a structure for forwarding of
adapter events and pass the address of this structure to firmware.

Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
[...]
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 156d1c25a3c1..9db6f8080f71 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -47,6 +47,7 @@
  #include <asm/fpu/api.h>
  #include "kvm-s390.h"
  #include "gaccess.h"
+#include "pci.h"
  #define CREATE_TRACE_POINTS
  #include "trace.h"
@@ -502,6 +503,14 @@ int kvm_arch_init(void *opaque)
          goto out;
      }
+    if (kvm_s390_pci_interp_allowed()) {
+        rc = kvm_s390_pci_init();
+        if (rc) {
+            pr_err("Unable to allocate AIFT for PCI\n");
+            goto out;
+        }
+    }
+
      rc = kvm_s390_gib_init(GAL_ISC);
      if (rc)
          goto out;

We would not free the aift that was allocated by kvm_s390_pci_init
in kvm_arch_exit.
Wouldnt we re-allocate a new aift when we unload/reload kvm forgetting about the old one?

Oops, yes it looks like that's the case. We must back-pocket a certain subset of firmware-shared structures (e.g. zpci_aipb and zpci_aif_sbv) as these cannot change for the life of the system once registered with firmware; but the aift is a kernel-only structure that should be safe to free until next module load. I think this can be done at the end of kvm_s390_pci_aen_exit (with some caller adjustments re: the aift mutex)


diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
[...]
+static int zpci_setup_aipb(u8 nisc)
[...]
+    size = get_order(PAGE_ALIGN(ZPCI_NR_DEVICES *
+                        sizeof(struct zpci_gaite)));
[...]
+    if (zpci_set_irq_ctrl(SIC_SET_AENI_CONTROLS, 0, zpci_aipb)) {
+        rc = -EIO;
+        goto free_gait;
+    }
+
+    return 0;
+
+free_gait:
+    size = get_order(PAGE_ALIGN(ZPCI_NR_DEVICES *
+                    sizeof(struct zpci_gaite)));

size should still be valid here?

Good point


+    free_pages((unsigned long)aift->gait, size);
+free_sbv:
+    airq_iv_release(aift->sbv);
+    zpci_aif_sbv = 0;
+free_aipb:
+    kfree(zpci_aipb);
+    zpci_aipb = 0;
+
+    return rc;
+}
+

The remaining parts look sane.




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