From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Aneesh Kumar K.V" Subject: Re: [PATCH v2] powernv: kvm: make _PAGE_NUMA take effect Date: Mon, 27 Jan 2014 15:58:45 +0530 Message-ID: <87wqhllnvm.fsf@linux.vnet.ibm.com> References: <1390292129-15871-1-git-send-email-pingfank@linux.vnet.ibm.com> <8761pdk6x5.fsf@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Liu Ping Fan , linuxppc-dev@lists.ozlabs.org, kvm-ppc , kvm-devel , Ben Herrenschmidt , Paul Mackerras To: Alexander Graf Return-path: In-Reply-To: Sender: kvm-ppc-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Alexander Graf writes: > On 21.01.2014, at 10:42, Aneesh Kumar K.V wrote: > >> Liu Ping Fan writes: >> >>> To make sure that on host, the pages marked with _PAGE_NUMA result in a fault >>> when guest access them, we should force the checking when guest uses hypercall >>> to setup hpte. >>> >>> Signed-off-by: Liu Ping Fan >> >> Reviewed-by: Aneesh Kumar K.V >> >> When we mark pte with _PAGE_NUMA we already call mmu_notifier_invalidate_range_start and >> mmu_notifier_invalidate_range_end, which will mark existing guest hpte >> entry as HPTE_V_ABSENT. Now we need to do that when we are inserting new >> guest hpte entries. This patch does that. > > So what happens next? We insert a page into the HTAB without > HPTE_V_VALID set, so the guest will fail to use it. If the guest does > an H_READ on it it will suddenly turn to V_VALID though? As per the guest the entry is valid, so yes an hread should return a valid entry. But in real hpte we would mark it not valid. > > I might need a crash course in the use of HPTE_V_ABSENT. When guest tries to access the address, the host will handle the fault. kvmppc_hpte_hv_fault should give more info -aneesh