powerpc/eeh: Restore initial state in eeh_pe_reset_and_recover()

commit 5a0cdbfd upstream.

The function eeh_pe_reset_and_recover() is used to recover EEH
error when the passthrou device are transferred to guest and
backwards. The content in the device's config space will be lost
on PE reset issued in the middle of the recovery. The function
saves/restores it before/after the reset. However, config access
to some adapters like Broadcom BCM5719 at this point will causes
fenced PHB. The config space is always blocked and we save 0xFF's
that are restored at late point. The memory BARs are totally
corrupted, causing another EEH error upon access to one of the
memory BARs.

This restores the config space on those adapters like BCM5719
from the content saved to the EEH device when it's populated,
to resolve above issue.

Fixes: 5cfb20b9 ("powerpc/eeh: Emulate EEH recovery for VFIO devices")
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

arch/powerpc/kernel/eeh_driver.c

@@ -188,6 +188,16 @@ static void *eeh_dev_save_state(void *data, void *userdata)
 	if (!edev)
 		return NULL;
 
+	/*
+	 * We cannot access the config space on some adapters.
+	 * Otherwise, it will cause fenced PHB. We don't save
+	 * the content in their config space and will restore
+	 * from the initial config space saved when the EEH
+	 * device is created.
+	 */
+	if (edev->pe && (edev->pe->state & EEH_PE_CFG_RESTRICTED))
+		return NULL;
+
 	pdev = eeh_dev_to_pci_dev(edev);
 	if (!pdev)
 		return NULL;
@@ -327,6 +337,19 @@ static void *eeh_dev_restore_state(void *data, void *userdata)
 	if (!edev)
 		return NULL;
 
+	/*
+	 * The content in the config space isn't saved because
+	 * the blocked config space on some adapters. We have
+	 * to restore the initial saved config space when the
+	 * EEH device is created.
+	 */
+	if (edev->pe && (edev->pe->state & EEH_PE_CFG_RESTRICTED)) {
+		if (list_is_last(&edev->list, &edev->pe->edevs))
+			eeh_pe_restore_bars(edev->pe);
+
+		return NULL;
+	}
+
 	pdev = eeh_dev_to_pci_dev(edev);
 	if (!pdev)
 		return NULL;