2017-11-05 21:52 GMT+08:00 Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>:
> 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@xxxxxxxxxx>
> Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Reviewed-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> 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 163d340ee5f8..4e822ad363f3 100644
> --- 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
> --
> 2.13.3
>
