Subject: [PATCH v2] powerpc/XIVE: SVM: share the event-queue page with the Hypervisor.

From: Ram Pai <[email-masked]>
Date: Thu, 26 Mar 2020 01:38:47 -0700

XIVE interrupt controller use an Event Queue (EQ) to enqueue event
notifications when an exception occurs. The EQ is a single memory page
provided by the O/S defining a circular buffer, one per server and
priority couple.

On baremetal, the EQ page is configured with an OPAL call. On pseries,
an extra hop is necessary and the guest OS uses the hcall
H_INT_SET_QUEUE_CONFIG to configure the XIVE interrupt controller.

The XIVE controller being Hypervisor privileged, it will not be allowed
to enqueue event notifications for a Secure VM unless the EQ pages are
shared by the Secure VM.

Hypervisor/Ultravisor still requires support for the TIMA and ESB page
fault handlers. Until this is complete, QEMU can use the emulated XIVE
device for Secure VMs, option "kernel_irqchip=off" on the QEMU pseries
machine.

Cc: [email-masked]
Cc: [email-masked]
Cc: Michael Ellerman <[email-masked]>
Cc: Thiago Jung Bauermann <[email-masked]>
Cc: Michael Anderson <[email-masked]>
Cc: Sukadev Bhattiprolu <[email-masked]>
Cc: Alexey Kardashevskiy <[email-masked]>
Cc: Paul Mackerras <[email-masked]>
Cc: Greg Kurz <[email-masked]>
Cc: Cedric Le Goater <[email-masked]>
Cc: David Gibson <[email-masked]>
Signed-off-by: Ram Pai <[email-masked]>

v2: better description of the patch from Cedric.
---
 arch/powerpc/sysdev/xive/spapr.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/powerpc/sysdev/xive/spapr.c b/arch/powerpc/sysdev/xive/spapr.c
index 55dc61c..608b52f 100644
--- a/arch/powerpc/sysdev/xive/spapr.c
+++ b/arch/powerpc/sysdev/xive/spapr.c
@@ -26,6 +26,8 @@
 #include <asm/xive.h>
 #include <asm/xive-regs.h>
 #include <asm/hvcall.h>
+#include <asm/svm.h>
+#include <asm/ultravisor.h>
 
 #include "xive-internal.h"
 
@@ -501,6 +503,9 @@ static int xive_spapr_configure_queue(u32 target, struct xive_q *q, u8 prio,
 		rc = -EIO;
 	} else {
 		q->qpage = qpage;
+		if (is_secure_guest())
+			uv_share_page(PHYS_PFN(qpage_phys),
+					1 << xive_alloc_order(order));
 	}
 fail:
 	return rc;
@@ -534,6 +539,8 @@ static void xive_spapr_cleanup_queue(unsigned int cpu, struct xive_cpu *xc,
 		       hw_cpu, prio);
 
 	alloc_order = xive_alloc_order(xive_queue_shift);
+	if (is_secure_guest())
+		uv_unshare_page(PHYS_PFN(__pa(q->qpage)), 1 << alloc_order);
 	free_pages((unsigned long)q->qpage, alloc_order);
 	q->qpage = NULL;
 }
-- 
1.8.3.1