Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933356AbbHJLTs (ORCPT ); Mon, 10 Aug 2015 07:19:48 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:5439 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933189AbbHJLTo (ORCPT ); Mon, 10 Aug 2015 07:19:44 -0400 X-IronPort-AV: E=Sophos;i="5.15,645,1432598400"; d="scan'208";a="292933803" Date: Mon, 10 Aug 2015 12:18:15 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Julien Grall CC: , , , , , Konrad Rzeszutek Wilk , Boris Ostrovsky , "David Vrabel" , Wei Liu Subject: Re: [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux In-Reply-To: <1438966019-19322-13-git-send-email-julien.grall@citrix.com> Message-ID: References: <1438966019-19322-1-git-send-email-julien.grall@citrix.com> <1438966019-19322-13-git-send-email-julien.grall@citrix.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6105 Lines: 184 On Fri, 7 Aug 2015, Julien Grall wrote: > For ARM64 guests, Linux is able to support either 64K or 4K page > granularity. Although, the hypercall interface is always based on 4K > page granularity. > > With 64K page granularity, a single page will be spread over multiple > Xen frame. > > To avoid splitting the page into 4K frame, take advantage of the > extent_order field to directly allocate/free chunk of the Linux page > size. > > Note that PVMMU is only used for PV guest (which is x86) and the page > granularity is always 4KB. Some BUILD_BUG_ON has been added to ensure > that because the code has not been modified. > > Signed-off-by: Julien Grall This is much better than the previous version. Good idea using the extent_order field. I only have a minor comment below. > --- > Cc: Konrad Rzeszutek Wilk > Cc: Boris Ostrovsky > Cc: David Vrabel > Cc: Wei Liu > > Changes in v3: > - Fix errors reported by checkpatch.pl > - s/mfn/gfn/ based on the new naming > - Rather than splitting the page into 4KB chunk, use the > extent_order field to allocate directly a Linux page size. This > is avoid lots of code for no benefits. > > Changes in v2: > - Use xen_apply_to_page to split a page in 4K chunk > - It's not necessary to have a smaller frame list. Re-use > PAGE_SIZE > - Convert reserve_additional_memory to use XEN_... macro > --- > drivers/xen/balloon.c | 47 ++++++++++++++++++++++++++++++++++++----------- > 1 file changed, 36 insertions(+), 11 deletions(-) > > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > index 9734649..c8739c8 100644 > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -70,6 +70,9 @@ > #include > #include > > +/* Use one extent per PAGE_SIZE to avoid break down into multiple frame */ > +#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1) > + > /* > * balloon_process() state: > * > @@ -230,6 +233,11 @@ static enum bp_state reserve_additional_memory(long credit) > nid = memory_add_physaddr_to_nid(hotplug_start_paddr); > > #ifdef CONFIG_XEN_HAVE_PVMMU > + /* We don't support PV MMU when Linux and Xen is using > + * different page granularity. > + */ > + BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE); > + > /* > * add_memory() will build page tables for the new memory so > * the p2m must contain invalid entries so the correct > @@ -326,11 +334,11 @@ static enum bp_state reserve_additional_memory(long credit) > static enum bp_state increase_reservation(unsigned long nr_pages) > { > int rc; > - unsigned long pfn, i; > + unsigned long i; > struct page *page; > struct xen_memory_reservation reservation = { > .address_bits = 0, > - .extent_order = 0, > + .extent_order = EXTENT_ORDER, > .domid = DOMID_SELF > }; > > @@ -352,7 +360,11 @@ static enum bp_state increase_reservation(unsigned long nr_pages) > nr_pages = i; > break; > } > - frame_list[i] = page_to_pfn(page); > + > + /* XENMEM_populate_physmap requires a PFN based on Xen > + * granularity. > + */ > + frame_list[i] = xen_page_to_pfn(page); > page = balloon_next_page(page); > } > > @@ -366,10 +378,15 @@ static enum bp_state increase_reservation(unsigned long nr_pages) > page = balloon_retrieve(false); > BUG_ON(page == NULL); > > - pfn = page_to_pfn(page); > - > #ifdef CONFIG_XEN_HAVE_PVMMU > + /* We don't support PV MMU when Linux and Xen is using > + * different page granularity. > + */ > + BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE); > + > if (!xen_feature(XENFEAT_auto_translated_physmap)) { > + unsigned long pfn = page_to_pfn(page); > + > set_phys_to_machine(pfn, frame_list[i]); > > /* Link back into the page tables if not highmem. */ > @@ -396,14 +413,15 @@ static enum bp_state increase_reservation(unsigned long nr_pages) > static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) > { > enum bp_state state = BP_DONE; > - unsigned long pfn, i; > + unsigned long i; > struct page *page; > int ret; > struct xen_memory_reservation reservation = { > .address_bits = 0, > - .extent_order = 0, > + .extent_order = EXTENT_ORDER, > .domid = DOMID_SELF > }; > + static struct page *pages[ARRAY_SIZE(frame_list)]; This array can be rather large: I would try to avoid it, see below. > #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG > if (balloon_stats.hotplug_pages) { > @@ -426,7 +444,9 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) > } > scrub_page(page); > > - frame_list[i] = page_to_pfn(page); > + /* XENMEM_decrease_reservation requires a GFN */ > + frame_list[i] = xen_page_to_gfn(page); > + pages[i] = page; > } > > /* > @@ -440,12 +460,17 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) > > /* Update direct mapping, invalidate P2M, and add to balloon. */ > for (i = 0; i < nr_pages; i++) { > - pfn = frame_list[i]; > - frame_list[i] = pfn_to_gfn(pfn); > - page = pfn_to_page(pfn); > + page = pages[i]; > > #ifdef CONFIG_XEN_HAVE_PVMMU > + /* We don't support PV MMU when Linux and Xen is using > + * different page granularity. > + */ > + BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE); > + > if (!xen_feature(XENFEAT_auto_translated_physmap)) { > + unsigned long pfn = page_to_pfn(page); I would simply and avoid introducing a new array: pfn = (frame_list[i] << XEN_PAGE_SHIFT) >> PAGE_SHIFT; page = pfn_to_page(pfn); > if (!PageHighMem(page)) { > ret = HYPERVISOR_update_va_mapping( > (unsigned long)__va(pfn << PAGE_SHIFT), > -- > 2.1.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/