Re: [Qemu-devel] [PATCH -V3 1/4] target-ppc: Update slb array with correct index values.

[Alexander Graf]

On 23.08.2013, at 06:20, Aneesh Kumar K.V wrote:

> From: "Aneesh Kumar K.V" <address@hidden>
> 
> Without this, a value of rb=0 and rs=0 results in replacing the 0th
> index. This can be observed when using gdb remote debugging support.
> 
> (gdb) x/10i do_fork
> 0xc000000000085330 <do_fork>:        Cannot access memory at address 
> 0xc000000000085330
> (gdb)
> 
> This is because when we do the slb sync via kvm_cpu_synchronize_state,
> we overwrite the slb entry (0th entry) for 0xc000000000085330
> 
> Signed-off-by: Aneesh Kumar K.V <address@hidden>
> ---
> target-ppc/kvm.c | 20 ++++++++++++++++++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index 30a870e..6878af2 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -1033,9 +1033,25 @@ int kvm_arch_get_registers(CPUState *cs)
> 
>     /* Sync SLB */
> #ifdef TARGET_PPC64
> +        /*
> +         * KVM_GET_SREGS doesn't return slb entry with slot information
> +         * same as index. The ioctl zero fills the array and update only
> +         * upto slb_max entries. We cannot depend on the slot value
> +         * in the slbe field for update, because a zero slbe value would
> +         * result in us wrongly updating the 0th index. Instead we zero fill
> +         * the env->slb array first so that we mark all entries invalid and
> +         * update with only valid SLB entries.

Still too negative. How about something like this:

/*
* The packed SLB array we get from KVM only contains information
*  about valid entries. So we flush our internal copy to get rid of stale
*  ones, then put all valid SLB entries back in.
*/

> +         */
> +        memset(env->slb, 0, 64 * sizeof(ppc_slb_t));

Can't we use ARRAY_SIZE here and below?


Alex

>     for (i = 0; i < 64; i++) {
> -            ppc_store_slb(env, sregs.u.s.ppc64.slb[i].slbe,
> -                               sregs.u.s.ppc64.slb[i].slbv);
> +            target_ulong rb = sregs.u.s.ppc64.slb[i].slbe;
> +            target_ulong rs = sregs.u.s.ppc64.slb[i].slbv;
> +            /*
> +             * Only restore valid entries
> +             */
> +            if (rb & SLB_ESID_V) {
> +                ppc_store_slb(env, rb, rs);
> +            }
>     }
> #endif
> 
> -- 
> 1.8.1.2
>