[PATCH v3] powerpc/XIVE: SVM: share the event-queue page with the Hypervisor.

[Ram Pai]

>From 10ea2eaf492ca3f22f67a5a63a2b7865e45299ad Mon Sep 17 00:00:00 2001
From: Ram Pai <linuxram at us.ibm.com>
Date: Mon, 24 Feb 2020 01:09:48 -0500
Subject: [PATCH v3] powerpc/XIVE: SVM: share the event-queue page with the
 Hypervisor.

XIVE interrupt controller uses 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: kvm-ppc at vger.kernel.org
Cc: linuxppc-dev at lists.ozlabs.org
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Thiago Jung Bauermann <bauerman at linux.ibm.com>
Cc: Michael Anderson <andmike at linux.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
Cc: Alexey Kardashevskiy <aik at ozlabs.ru>
Cc: Paul Mackerras <paulus at ozlabs.org>
Cc: David Gibson <david at gibson.dropbear.id.au>
Reviewed-by: Cedric Le Goater <clg at kaod.org>
Reviewed-by: Greg Kurz <groug at kaod.org>
Signed-off-by: Ram Pai <linuxram at us.ibm.com>

v3: fix a minor semantics in description.
    and added reviewed-by from Cedric and Greg.
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