From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 05D7E6B050D for ; Tue, 11 Jul 2017 10:57:50 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id u71so1504714qkl.8 for ; Tue, 11 Jul 2017 07:57:50 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id d78si116670qkc.297.2017.07.11.07.57.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Jul 2017 07:57:49 -0700 (PDT) Date: Tue, 11 Jul 2017 10:57:44 -0400 From: Jerome Glisse Subject: Re: [PATCH 2/5] mm/device-public-memory: device memory cache coherent with CPU v2 Message-ID: <20170711145744.GA5347@redhat.com> References: <20170703211415.11283-1-jglisse@redhat.com> <20170703211415.11283-3-jglisse@redhat.com> <20170711141215.4fd1a972@firefly.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170711141215.4fd1a972@firefly.ozlabs.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Balbir Singh Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, John Hubbard , David Nellans , Dan Williams , Balbir Singh , Aneesh Kumar , "Paul E . McKenney" , Benjamin Herrenschmidt , Ross Zwisler On Tue, Jul 11, 2017 at 02:12:15PM +1000, Balbir Singh wrote: > On Mon, 3 Jul 2017 17:14:12 -0400 > Jerome Glisse wrote: > > > Platform with advance system bus (like CAPI or CCIX) allow device > > memory to be accessible from CPU in a cache coherent fashion. Add > > a new type of ZONE_DEVICE to represent such memory. The use case > > are the same as for the un-addressable device memory but without > > all the corners cases. > > > > Looks good overall, some comments inline. > [...] > > /* > > @@ -92,6 +100,8 @@ enum memory_type { > > * The page_free() callback is called once the page refcount reaches 1 > > * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug. > > * This allows the device driver to implement its own memory management.) > > + * > > + * For MEMORY_DEVICE_CACHE_COHERENT only the page_free() callback matter. > > Correct, but I wonder if we should in the long term allow for minor faults > (due to coherency) via this interface? This is something we can explore latter on. [...] > > diff --git a/kernel/memremap.c b/kernel/memremap.c > > index e82456c39a6a..da74775f2247 100644 > > --- a/kernel/memremap.c > > +++ b/kernel/memremap.c > > @@ -466,7 +466,7 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) > > > > > > #ifdef CONFIG_DEVICE_PRIVATE > > Does the #ifdef above need to go as well? Good catch i should make that conditional on DEVICE_PUBLIC or whatever the name endup to be. I will make sure i test without DEVICE_PRIVATE config before posting again. [...] > > @@ -2541,11 +2551,21 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate, > > */ > > __SetPageUptodate(page); > > > > - if (is_zone_device_page(page) && is_device_private_page(page)) { > > - swp_entry_t swp_entry; > > + if (is_zone_device_page(page)) { > > + if (is_device_private_page(page)) { > > + swp_entry_t swp_entry; > > > > - swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE); > > - entry = swp_entry_to_pte(swp_entry); > > + swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE); > > + entry = swp_entry_to_pte(swp_entry); > > + } > > +#if IS_ENABLED(CONFIG_DEVICE_PUBLIC) > > Do we need this #if check? is_device_public_page(page) > will return false if the config is disabled pte_mkdevmap() is not define if ZONE_DEVICE is not enabled hence i had to protect this with #if/#endif to avoid build error. > > > + else if (is_device_public_page(page)) { > > + entry = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot))); > > + if (vma->vm_flags & VM_WRITE) > > + entry = pte_mkwrite(pte_mkdirty(entry)); > > + entry = pte_mkdevmap(entry); > > + } > > +#endif /* IS_ENABLED(CONFIG_DEVICE_PUBLIC) */ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org