Patch "KVM: x86: ioapic: Preserve read-only values in the redirection table" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

KVM: x86: ioapic: Preserve read-only values in the redirection table

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-x86-ioapic-preserve-read-only-values-in-the-redirection-table.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nikita Leshenko <[email protected]>
Date: Sun, 5 Nov 2017 15:52:33 +0200
Subject: KVM: x86: ioapic: Preserve read-only values in the redirection table

From: Nikita Leshenko <[email protected]>

[ Upstream commit b200dded0a6974a3b69599832b2203483920ab25 ]

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").

---
 arch/x86/kvm/ioapic.c |    6 ++++++
 1 file changed, 6 insertions(+)

@@ -278,6 +278,7 @@ static void ioapic_write_indirect(struct
 {
 	unsigned index;
 	bool mask_before, mask_after;
+	int old_remote_irr, old_delivery_status;
 	union kvm_ioapic_redirect_entry *e;
 
 	switch (ioapic->ioregsel) {

@@ -300,6 +301,9 @@ static void ioapic_write_indirect(struct
 			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;

@@ -307,6 +311,8 @@ static void ioapic_write_indirect(struct
 			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

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kvm-x86-don-t-re-execute-instruction-when-not-passing-cr2-value.patch queue-4.9/kvm-x86-ioapic-preserve-read-only-values-in-the-redirection-table.patch queue-4.9/kvm-x86-ioapic-fix-level-triggered-eoi-and-ioapic-reconfigure-race.patch queue-4.9/kvm-x86-emulator-return-to-user-mode-on-l1-cpl-0-emulation-failure.patch queue-4.9/kvm-x86-ioapic-clear-remote-irr-when-entry-is-switched-to-edge-triggered.patch