Re: [PATCH v3 6/9] MIPS: KVM: Restore correct value for WIRED at TLB uninit

[James Hogan <james.hogan@imgtec.com>]

On 24/06/14 18:31, Deng-Cheng Zhu wrote:
> From: Deng-Cheng Zhu <dengcheng.zhu@imgtec.com>
> 
> At TLB initialization, the commpage TLB entry is reserved on top of the
> existing WIRED entries (the number not necessarily be 0).
> 
> Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@imgtec.com>
> ---
>  arch/mips/kvm/mips.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 27250ee..3d53d34 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -170,7 +170,7 @@ void kvm_arch_sync_events(struct kvm *kvm)
>  static void kvm_mips_uninit_tlbs(void *arg)
>  {
>  	/* Restore wired count */
> -	write_c0_wired(0);
> +	write_c0_wired(read_c0_wired() - 1);
>  	mtc0_tlbw_hazard();
>  	/* Clear out all the TLBs */
>  	kvm_local_flush_tlb_all();

kvm_local_flush_tlb_all blasts all the entries away regardless of wired,
so I don't think this is an improvement.

I suspect to really be safe/correct in the presence of other dynamic
users of wired it would have to either manage arbitrary
allocation/deallocation of per-cpu tlb entries correctly from a single
place, or abandon the use of wired altogether.

Cheers
James