Re: [PATCH 5/5] KVM: x86: ioapic: Preserve read-only values in the redirection table

[Wanpeng Li <kernellwp@gmail.com>]

2017-11-05 21:52 GMT+08:00 Nikita Leshenko <nikita.leshchenko@oracle.com>:
> 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>

> ---
>  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
>