From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39305) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VDqZV-00037c-Ke for qemu-devel@nongnu.org; Mon, 26 Aug 2013 02:46:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VDqZN-0005uX-RD for qemu-devel@nongnu.org; Mon, 26 Aug 2013 02:46:41 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:49992) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VDqZL-0005tA-LV for qemu-devel@nongnu.org; Mon, 26 Aug 2013 02:46:33 -0400 Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 26 Aug 2013 16:39:09 +1000 From: "Aneesh Kumar K.V" In-Reply-To: References: <1377235210-27093-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1377235210-27093-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Date: Mon, 26 Aug 2013 12:16:09 +0530 Message-ID: <87mwo5dk5q.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH -V3 1/4] target-ppc: Update slb array with correct index values. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: "qemu-ppc@nongnu.org list:PowerPC" , Paul Mackerras , "qemu-devel@nongnu.org qemu-devel" Alexander Graf writes: > On 23.08.2013, at 06:20, Aneesh Kumar K.V wrote: > >> From: "Aneesh Kumar K.V" >> >> 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 : 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 >> --- >> 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. > */ updated > >> + */ >> + memset(env->slb, 0, 64 * sizeof(ppc_slb_t)); > > Can't we use ARRAY_SIZE here and below? I was thinking we want to be explicit there saying we are zeroing out all the 64 entries. I could do sizeof(env->slb). -anesh