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Subject: Re: [Xen-devel] xen: Can't insert balloon page into VM userspace (WAS
 Re: [linux-linus bisection] complete test-arm64-arm64-xl-xsm)
To:     Julien Grall <julien.grall@arm.com>,
        Juergen Gross <jgross@suse.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        Matthew Wilcox <willy@infradead.org>
Cc:     k.khlebnikov@samsung.com,
        Stefano Stabellini <sstabellini@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        "VMware, Inc." <pv-drivers@vmware.com>,
        osstest service owner <osstest-admin@xenproject.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org, Julien Freche <jfreche@vmware.com>,
        Nadav Amit <namit@vmware.com>, xen-devel@lists.xenproject.org
References: <E1h3Uiq-0002L6-Ij@osstest.test-lab.xenproject.org>
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 <e0b64793-260d-5e70-0544-e7290509b605@redhat.com>
 <45323ea0-2a50-8891-830e-e1f8a8ed23ea@citrix.com>
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 <ec71c03e-987d-2b73-9fe6-2604a3c32017@suse.com>
 <cb525882-b52f-c142-8a6a-e5cb491e05d0@arm.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <f02aa953-d5d1-4e78-160f-9bca1516379f@redhat.com>
Date:   Thu, 14 Mar 2019 15:14:56 +0100
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In-Reply-To: <cb525882-b52f-c142-8a6a-e5cb491e05d0@arm.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On 14.03.19 15:12, Julien Grall wrote:
> Hi,
> 
> On 3/14/19 8:37 AM, Juergen Gross wrote:
>> On 12/03/2019 20:46, David Hildenbrand wrote:
>>> On 12.03.19 19:23, David Hildenbrand wrote:
>>>
>>> I guess something like this could do the trick if I understood it correctly:
>>>
>>> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
>>> index 39b229f9e256..d37dd5bb7a8f 100644
>>> --- a/drivers/xen/balloon.c
>>> +++ b/drivers/xen/balloon.c
>>> @@ -604,6 +604,7 @@ int alloc_xenballooned_pages(int nr_pages, struct
>>> page **pages)
>>>          while (pgno < nr_pages) {
>>>                  page = balloon_retrieve(true);
>>>                  if (page) {
>>> +                       __ClearPageOffline(page);
>>>                          pages[pgno++] = page;
>>>   #ifdef CONFIG_XEN_HAVE_PVMMU
>>>                          /*
>>> @@ -645,8 +646,10 @@ void free_xenballooned_pages(int nr_pages, struct
>>> page **pages)
>>>          mutex_lock(&balloon_mutex);
>>>
>>>          for (i = 0; i < nr_pages; i++) {
>>> -               if (pages[i])
>>> +               if (pages[i]) {
>>> +                       __SetPageOffline(pages[i]);
>>>                          balloon_append(pages[i]);
>>> +               }
>>>          }
>>>
>>>          balloon_stats.target_unpopulated -= nr_pages;
>>>
>>>
>>> At least this way, the pages allocated (and thus eventually mapped to
>>> user space) would not be marked, but the other ones would remain marked
>>> and could be excluded by makedumptool.
>>>
>>
>> I think this patch should do the trick. Julien, could you give it a
>> try? On x86 I can't reproduce your problem easily as dom0 is PV with
>> plenty of unpopulated pages for grant memory not suffering from
>> missing "offline" bit.
> 
> Sure. I managed to get the console working with the patch suggested by 
> David. Feel free to add my tested-by if when you resend it as is.
> 

Thanks, I will send as proper patch later!

Cheers!

> Cheers,
> 


-- 

Thanks,

David / dhildenb