[PATCH AUTOSEL for 4.4 06/35] KVM: x86: ioapic: Preserve read-only values in the redirection table

Sasha Levin
2018-01-24T04:31:24Z

From: Nikita Leshenko <nikita.leshchenko@oracle.com>

[ 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").

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
arch/x86/kvm/ioapic.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index 403dd464965c..d380111351c0 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -268,6 +268,7 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
{
unsigned index;
bool mask_before, mask_after;
+ int old_remote_irr, old_delivery_status;
union kvm_ioapic_redirect_entry *e;

switch (ioapic->ioregsel) {
@@ -290,6 +291,9 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
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;
@@ -297,6 +301,8 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
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
--
2.11.0