Re: [PATCH v2] KVM: IOAPIC: only access APIC registers one dword at a time

Marcelo Tosatti
2010-07-02T17:45:20Z

On Fri, Jul 02, 2010 at 04:00:12PM +0800, Xiao Guangrong wrote:
> The IOAPIC spec says:
>
> When accessing these registers, accesses must be done one dword at a time.
> For example, software should never access byte 2 from the Data register before
> accessing bytes 0 and 1. The hardware will not attempt to recover from a bad
> programming model in this case.
>
> So, this patch removes other width access
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> ---
> virt/kvm/ioapic.c | 20 +++++++-------------
> 1 files changed, 7 insertions(+), 13 deletions(-)
>
> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> index 1149c60..6610d11 100644
> --- a/virt/kvm/ioapic.c
> +++ b/virt/kvm/ioapic.c
> @@ -288,6 +288,11 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
> ioapic_debug("addr %lx\n", (unsigned long)addr);
> ASSERT(!(addr & 0xf)); /* check alignment */
>
> + if (len != 4) {
> + printk(KERN_WARNING "ioapic: wrong length %d\n", len);
> + return 0;
> + }
> +

Just remove the printks please, as guests can flood hosts dmesg.