s390/pci: improve error handling during interrupt deregistration

When we ask a function to stop creating interrupts this may fail
due to the function being already gone (e.g. after hot-unplug).

Consequently we don't free associated resources like summary bits
and bit vectors used for irq processing. This could lead to
situations where we ran out of these resources and fail to setup
new interrupts.

The fix is to just ignore the errors in cases where we can be
sure no new interrupts are generated.

Signed-off-by: Sebastian Ott <[e-mail]>
Reviewed-by: Gerald Schaefer <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/include/asm/pci_insn.h

···
 	u32 gd;
 } __packed __aligned(8);
 
-int zpci_mod_fc(u64 req, struct zpci_fib *fib);
+u8 zpci_mod_fc(u64 req, struct zpci_fib *fib, u8 *status);
 int zpci_refresh_trans(u64 fn, u64 addr, u64 range);
 int zpci_load(u64 *data, u64 req, u64 offset);
 int zpci_store(u64 data, u64 req, u64 offset);

arch/s390/pci/pci.c

···
 {
 	u64 req = ZPCI_CREATE_REQ(zdev->fh, 0, ZPCI_MOD_FC_REG_INT);
 	struct zpci_fib fib = {0};
+	u8 status;
 
 	fib.isc = PCI_ISC;
 	fib.sum = 1;		/* enable summary notifications */
···
 	fib.aisb = (unsigned long) zpci_aisb_iv->vector + (zdev->aisb/64)*8;
 	fib.aisbo = zdev->aisb & 63;
 
-	return zpci_mod_fc(req, &fib);
+	return zpci_mod_fc(req, &fib, &status) ? -EIO : 0;
+}
+
+/* Modify PCI: Unregister adapter interruptions */
+static int zpci_clear_airq(struct zpci_dev *zdev)
+{
+	u64 req = ZPCI_CREATE_REQ(zdev->fh, 0, ZPCI_MOD_FC_DEREG_INT);
+	struct zpci_fib fib = {0};
+	u8 cc, status;
+
+	cc = zpci_mod_fc(req, &fib, &status);
+	if (cc == 3 || (cc == 1 && status == 24))
+		/* Function already gone or IRQs already deregistered. */
+		cc = 0;
+
+	return cc ? -EIO : 0;
 }
 
 struct mod_pci_args {
···
 {
 	u64 req = ZPCI_CREATE_REQ(zdev->fh, dmaas, fn);
 	struct zpci_fib fib = {0};
+	u8 status;
 
 	fib.pba = args->base;
 	fib.pal = args->limit;
 	fib.iota = args->iota;
 	fib.fmb_addr = args->fmb_addr;
 
-	return zpci_mod_fc(req, &fib);
+	return zpci_mod_fc(req, &fib, &status) ? -EIO : 0;
 }
 
 /* Modify PCI: Register I/O address translation parameters */
···
 	struct mod_pci_args args = { 0, 0, 0, 0 };
 
 	return mod_pci(zdev, ZPCI_MOD_FC_DEREG_IOAT, dmaas, &args);
-}
-
-/* Modify PCI: Unregister adapter interruptions */
-static int zpci_clear_airq(struct zpci_dev *zdev)
-{
-	struct mod_pci_args args = { 0, 0, 0, 0 };
-
-	return mod_pci(zdev, ZPCI_MOD_FC_DEREG_INT, 0, &args);
 }
 
 /* Modify PCI: Set PCI function measurement parameters */

arch/s390/pci/pci_insn.c

···
 	return cc;
 }
 
-int zpci_mod_fc(u64 req, struct zpci_fib *fib)
+u8 zpci_mod_fc(u64 req, struct zpci_fib *fib, u8 *status)
 {
-	u8 cc, status;
+	u8 cc;
 
 	do {
-		cc = __mpcifc(req, fib, &status);
+		cc = __mpcifc(req, fib, status);
 		if (cc == 2)
 			msleep(ZPCI_INSN_BUSY_DELAY);
 	} while (cc == 2);
 
 	if (cc)
-		zpci_err_insn(cc, status, req, 0);
+		zpci_err_insn(cc, *status, req, 0);
 
-	return (cc) ? -EIO : 0;
+	return cc;
 }
 
 /* Refresh PCI Translations */