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

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>

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index 163d340ee5f8286bd7a27a068d601280af8345a5..4e822ad363f37f613d14ab94f35609bcf3539bf7 100644 (file)
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -276,6 +276,7 @@ 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) {
@@ -298,6 +299,9 @@ 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;
@@ -305,6 +309,8 @@ 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