cxl: Poll for outstanding IRQs when detaching a context

When detaching contexts, we may still have interrupts in the system
which are yet to be delivered to any CPU and be acked in the PSL.
This can result in a subsequent unrelated process getting an spurious
IRQ or an interrupt for a non-existent context.

This polls the PSL to ensure that the PSL is clear of IRQs for the
detached context, before removing the context from the idr.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Tested-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Tested-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/misc/cxl/native.c b/drivers/misc/cxl/native.c
index 387fcbdf9793..ecf7557cd657 100644
--- a/drivers/misc/cxl/native.c
+++ b/drivers/misc/cxl/native.c
@@ -14,6 +14,7 @@
 #include <linux/mutex.h>
 #include <linux/mm.h>
 #include <linux/uaccess.h>
+#include <linux/delay.h>
 #include <asm/synch.h>
 #include <misc/cxl-base.h>
 
@@ -797,6 +798,35 @@ static irqreturn_t native_irq_multiplexed(int irq, void *data)
         return fail_psl_irq(afu, &irq_info);
 }
 
+void native_irq_wait(struct cxl_context *ctx)
+{
+        u64 dsisr;
+        int timeout = 1000;
+        int ph;
+
+        /*
+         * Wait until no further interrupts are presented by the PSL
+         * for this context.
+         */
+        while (timeout--) {
+                ph = cxl_p2n_read(ctx->afu, CXL_PSL_PEHandle_An) & 0xffff;
+                if (ph != ctx->pe)
+                        return;
+                dsisr = cxl_p2n_read(ctx->afu, CXL_PSL_DSISR_An);
+                if ((dsisr & CXL_PSL_DSISR_PENDING) == 0)
+                        return;
+                /*
+                 * We are waiting for the workqueue to process our
+                 * irq, so need to let that run here.
+                 */
+                msleep(1);
+        }
+
+        dev_warn(&ctx->afu->dev, "WARNING: waiting on DSI for PE %i"
+                 " DSISR %016llx!\n", ph, dsisr);
+        return;
+}
+
 static irqreturn_t native_slice_irq_err(int irq, void *data)
 {
         struct cxl_afu *afu = data;
@@ -1076,6 +1106,7 @@ const struct cxl_backend_ops cxl_native_ops = {
         .handle_psl_slice_error = native_handle_psl_slice_error,
         .psl_interrupt = NULL,
         .ack_irq = native_ack_irq,
+        .irq_wait = native_irq_wait,
         .attach_process = native_attach_process,
         .detach_process = native_detach_process,
         .support_attributes = native_support_attributes,