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Re: [Xen-devel] [PATCH v1 09/10] mm/memory_hotplug: Don't mark pages PG_reserved when initializing the memmap
- To: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx
- From: David Hildenbrand <david@xxxxxxxxxx>
- Date: Tue, 5 Nov 2019 11:18:49 +0100
- Cc: linux-hyperv@xxxxxxxxxxxxxxx, Michal Hocko <mhocko@xxxxxxxx>, Radim Krčmář <rkrcmar@xxxxxxxxxx>, kvm@xxxxxxxxxxxxxxx, Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>, KarimAllah Ahmed <karahmed@xxxxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, Alexander Duyck <alexander.duyck@xxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxxx>, linux-mm@xxxxxxxxx, Paul Mackerras <paulus@xxxxxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Wanpeng Li <wanpengli@xxxxxxxxxxx>, Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>, "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>, devel@xxxxxxxxxxxxxxxxxxxx, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>, "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, x86@xxxxxxxxxx, YueHaibing <yuehaibing@xxxxxxxxxx>, "Matthew Wilcox \(Oracle\)" <willy@xxxxxxxxxxxxx>, Mike Rapoport <rppt@xxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Vlastimil Babka <vbabka@xxxxxxx>, Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>, Oscar Salvador <osalvador@xxxxxxx>, "Isaac J. Manjarres" <isaacm@xxxxxxxxxxxxxx>, Matt Sickler <Matt.Sickler@xxxxxxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Anshuman Khandual <anshuman.khandual@xxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, Sasha Levin <sashal@xxxxxxxxxx>, kvm-ppc@xxxxxxxxxxxxxxx, Qian Cai <cai@xxxxxx>, Alex Williamson <alex.williamson@xxxxxxxxxx>, Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Nicholas Piggin <npiggin@xxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Dan Williams <dan.j.williams@xxxxxxxxx>, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Allison Randal <allison@xxxxxxxxxxx>, Jim Mattson <jmattson@xxxxxxxxxx>, Christophe Leroy <christophe.leroy@xxxxxx>, Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>, Cornelia Huck <cohuck@xxxxxxxxxx>, Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>, Sean Christopherson <sean.j.christopherson@xxxxxxxxx>, Johannes Weiner <hannes@xxxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, linuxppc-dev@xxxxxxxxxxxxxxxx
- Delivery-date: Tue, 05 Nov 2019 10:19:29 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04.11.19 23:44, Boris Ostrovsky wrote:
On 10/24/19 8:09 AM, David Hildenbrand wrote:
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 4f2e78a5e4db..af69f057913a 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -374,6 +374,13 @@ static void xen_online_page(struct page *page, unsigned
int order)
mutex_lock(&balloon_mutex);
for (i = 0; i < size; i++) {
p = pfn_to_page(start_pfn + i);
+ /*
+ * TODO: The core used to mark the pages reserved. Most probably
+ * we can stop doing that now. However, especially
+ * alloc_xenballooned_pages() left PG_reserved set
+ * on pages that can get mapped to user space.
+ */
+ __SetPageReserved(p);
I suspect this is not needed. Pages can get into balloon either from
here or from non-hotplug path (e.g. decrease_reservation()) and so when
we get a page from the balloon we would get a random page that may or
may not have Reserved bit set.
Yeah, I also think it is fine. If you agree, I'll drop this hunk and add
details to the patch description.
--
Thanks,
David / dhildenb
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