From: Nikita Leshenko <nikita.leshchenko@oracle.com>
Date: Sun, 5 Nov 2017 15:52:33 +0200
Subject: KVM: x86: ioapic: Preserve read-only values in the redirection table
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Patch-mainline: v4.15-rc2
Git-commit: b200dded0a6974a3b69599832b2203483920ab25
References: bsc#1077761

According to 82093AA (IOAPIC) manual, Remote IRR and Delivery Status are
read-only. QEMU implements the bits as RO in commit 479c2a1cb7fb
("ioapic: keep RO bits for IOAPIC entry").

Signed-off-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
---
 arch/x86/kvm/ioapic.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -276,6 +276,7 @@
 {
 	unsigned index;
 	bool mask_before, mask_after;
+	int old_remote_irr, old_delivery_status;
 	union kvm_ioapic_redirect_entry *e;
 
 	switch (ioapic->ioregsel) {
@@ -298,6 +299,9 @@
 			return;
 		e = &ioapic->redirtbl[index];
 		mask_before = e->fields.mask;
+		/* Preserve read-only fields */
+		old_remote_irr = e->fields.remote_irr;
+		old_delivery_status = e->fields.delivery_status;
 		if (ioapic->ioregsel & 1) {
 			e->bits &= 0xffffffff;
 			e->bits |= (u64) val << 32;
@@ -305,6 +309,8 @@
 			e->bits &= ~0xffffffffULL;
 			e->bits |= (u32) val;
 		}
+		e->fields.remote_irr = old_remote_irr;
+		e->fields.delivery_status = old_delivery_status;
 
 		/*
 		 * Some OSes (Linux, Xen) assume that Remote IRR bit will