[V3 PATCH 11/16] powerpc/pseries/vas: Setup IRQ and fault handling

Haren Myneni
2021-04-17T21:09:51Z

When NX sees a fault on the user space buffer, generates a fault
interrupt and pHyp forwards that interrupt to OS. Then the kernel
makes H_GET_NX_FAULT HCALL to retrieve the fault CRB information.

This patch adds changes to setup IRQ per each window and handles
fault by updating CSB.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
---
arch/powerpc/platforms/pseries/vas.c | 111 ++++++++++++++++++++++++++-
1 file changed, 110 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index 0ade0d6d728f..2106eca0862a 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -224,6 +224,62 @@ int plpar_vas_query_capabilities(const u64 hcall, u8 query_type,
}
EXPORT_SYMBOL_GPL(plpar_vas_query_capabilities);

+/*
+ * HCALL to get fault CRB from pHyp.
+ */
+static int plpar_get_nx_fault(u32 winid, u64 buffer)
+{
+ int64_t rc;
+
+ rc = plpar_hcall_norets(H_GET_NX_FAULT, winid, buffer);
+
+ switch (rc) {
+ case H_SUCCESS:
+ return 0;
+ case H_PARAMETER:
+ pr_err("HCALL(%x): Invalid window ID %u\n", H_GET_NX_FAULT,
+ winid);
+ return -EINVAL;
+ case H_STATE:
+ pr_err("HCALL(%x): No outstanding faults for window ID %u\n",
+ H_GET_NX_FAULT, winid);
+ return -EINVAL;
+ case H_PRIVILEGE:
+ pr_err("HCALL(%x): Window(%u): Invalid fault buffer 0x%llx\n",
+ H_GET_NX_FAULT, winid, buffer);
+ return -EACCES;
+ default:
+ pr_err("HCALL(%x): Unexpected error %lld for window(%u)\n",
+ H_GET_NX_FAULT, rc, winid);
+ return -EIO;
+ }
+}
+
+/*
+ * Handle the fault interrupt.
+ * When the fault interrupt is received for each window, query pHyp to get
+ * the fault CRB on the specific fault. Then process the CRB by updating
+ * CSB or send signal if the user space CSB is invalid.
+ * Note: pHyp forwards an interrupt for each fault request. So one fault
+ * CRB to process for each H_GET_NX_FAULT HCALL.
+ */
+irqreturn_t pseries_vas_fault_thread_fn(int irq, void *data)
+{
+ struct vas_window *txwin = data;
+ struct coprocessor_request_block crb;
+ struct vas_win_task *tsk;
+ int rc;
+
+ rc = plpar_get_nx_fault(txwin->winid, (u64)virt_to_phys(&crb));
+ if (!rc) {
+ tsk = &txwin->task;
+ vas_dump_crb(&crb);
+ vas_update_csb(&crb, tsk);
+ }
+
+ return IRQ_HANDLED;
+}
+
/*
* Allocate window and setup IRQ mapping.
*/
@@ -235,10 +291,51 @@ static int allocate_setup_window(struct vas_window *txwin,
rc = plpar_vas_allocate_window(txwin, domain, wintype, DEF_WIN_CREDS);
if (rc)
return rc;
+ /*
+ * On powerVM, pHyp setup and forwards the fault interrupt per
+ * window. So the IRQ setup and fault handling will be done for
+ * each open window separately.
+ */
+ txwin->lpar.fault_virq = irq_create_mapping(NULL,
+ txwin->lpar.fault_irq);
+ if (!txwin->lpar.fault_virq) {
+ pr_err("Failed irq mapping %d\n", txwin->lpar.fault_irq);
+ rc = -EINVAL;
+ goto out_win;
+ }
+
+ txwin->lpar.name = kasprintf(GFP_KERNEL, "vas-win-%d", txwin->winid);
+ if (!txwin->lpar.name) {
+ rc = -ENOMEM;
+ goto out_irq;
+ }
+
+ rc = request_threaded_irq(txwin->lpar.fault_virq, NULL,
+ pseries_vas_fault_thread_fn, IRQF_ONESHOT,
+ txwin->lpar.name, txwin);
+ if (rc) {
+ pr_err("VAS-Window[%d]: Request IRQ(%u) failed with %d\n",
+ txwin->winid, txwin->lpar.fault_virq, rc);
+ goto out_free;
+ }

txwin->wcreds_max = DEF_WIN_CREDS;

return 0;
+out_free:
+ kfree(txwin->lpar.name);
+out_irq:
+ irq_dispose_mapping(txwin->lpar.fault_virq);
+out_win:
+ plpar_vas_deallocate_window(txwin->winid);
+ return rc;
+}
+
+static inline void free_irq_setup(struct vas_window *txwin)
+{
+ free_irq(txwin->lpar.fault_virq, txwin);
+ irq_dispose_mapping(txwin->lpar.fault_virq);
+ kfree(txwin->lpar.name);
}

static struct vas_window *vas_allocate_window(struct vas_tx_win_open_attr *uattr,
@@ -346,6 +443,11 @@ static struct vas_window *vas_allocate_window(struct vas_tx_win_open_attr *uattr
return txwin;

out_free:
+ /*
+ * Window is not operational. Free IRQ before closing
+ * window so that do not have to hold mutex.
+ */
+ free_irq_setup(txwin);
plpar_vas_deallocate_window(txwin->winid);
out:
atomic_dec(&ct_capab->used_lpar_creds);
@@ -364,9 +466,16 @@ static int deallocate_free_window(struct vas_window *win)
{
int rc = 0;

+ /*
+ * Free IRQ after executing H_DEALLOCATE_VAS_WINDOW HCALL
+ * to close the window. pHyp waits for all requests including
+ * faults are processed before closing the window - Means all
+ * credits are returned. In the case of fault request, credit
+ * is returned after OS issues H_GET_NX_FAULT HCALL.
+ */
rc = plpar_vas_deallocate_window(win->winid);
if (!rc)
- kfree(win->lpar.name);
+ free_irq_setup(win);

return rc;
}
--
2.18.2