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Date:   Fri, 22 Jun 2018 10:51:27 +0800
From:   Baoquan He <bhe@redhat.com>
To:     lijiang <lijiang@redhat.com>
Cc:     thomas.lendacky@amd.com, iommu@lists.linux-foundation.org,
        dyoung@redhat.com, linux-kernel@vger.kernel.org,
        kexec@lists.infradead.org
Subject: Re: [PATCH 2/4 V3] Allocate pages for kdump without encryption when
 SME is enabled
Message-ID: <20180622025127.GM29979@MiWiFi-R3L-srv>
References: <20180616082714.32035-1-lijiang@redhat.com>
 <20180616082714.32035-3-lijiang@redhat.com>
 <20180621015306.GG29979@MiWiFi-R3L-srv>
 <e74e94b6-97dc-23d9-6262-44a7ae8d63bd@redhat.com>
 <20180621102321.GK29979@MiWiFi-R3L-srv>
 <49706f0e-03b6-8c43-c35f-c0b0338a17bd@redhat.com>
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On 06/21/18 at 09:27pm, lijiang wrote:
> 在 2018年06月21日 18:23, Baoquan He 写道:
> > On 06/21/18 at 01:06pm, lijiang wrote:
> >> 在 2018年06月21日 09:53, Baoquan He 写道:
> >>> On 06/16/18 at 04:27pm, Lianbo Jiang wrote:
> >>>> When SME is enabled in the first kernel, we will allocate pages
> >>>> for kdump without encryption in order to be able to boot the
> >>>> second kernel in the same manner as kexec, which helps to keep
> >>>> the same code style.
> >>>>
> >>>> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
> >>>> ---
> >>>>  kernel/kexec_core.c | 12 ++++++++++++
> >>>>  1 file changed, 12 insertions(+)
> >>>>
> >>>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> >>>> index 20fef1a..3c22a9b 100644
> >>>> --- a/kernel/kexec_core.c
> >>>> +++ b/kernel/kexec_core.c
> >>>> @@ -471,6 +471,16 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
> >>>>  		}
> >>>>  	}
> >>>>  
> >>>> +	if (pages) {
> >>>> +		unsigned int count, i;
> >>>> +
> >>>> +		pages->mapping = NULL;
> >>>> +		set_page_private(pages, order);
> >>>> +		count = 1 << order;
> >>>> +		for (i = 0; i < count; i++)
> >>>> +			SetPageReserved(pages + i);
> >>>
> >>> I guess you might imitate the kexec case, however kexec get pages from
> >>> buddy. Crash pages are reserved in memblock, these codes might make no sense.
> >>>
> >> Thanks for your comments.
> >> We have changed the attribute of pages, so the original attribute of pages will be
> >> restored when they free.
> > 
> > Hmm, you can check what kimage_free() is doing, and where
> > kimage->control_pages, dest_pages, unusable_pages is assigned. Do you
> > know where these original attribute of pages comes from and they are
> > used/needed in CRASH case, if you care about them?
> > 
> Originally, we want to have an opportunity to restore the previous attribute of pages, that
> should be more better if the pages are remembered in 'image->control_pages'.

Again, please check who assigns value for 'image->control_pages'.

> If we remove these codes, it is also harmless for kdump, but it will become strange, maybe
> someone could ask where to restore the previous attribute of pages.
> 
> Thanks.
> >>
> >>>> +		arch_kexec_post_alloc_pages(page_address(pages), 1 << order, 0);
> >>>> +	}
> >>>>  	return pages;
> >>>>  }
> >>>>  
> >>>> @@ -865,6 +875,7 @@ static int kimage_load_crash_segment(struct kimage *image,
> >>>>  			result  = -ENOMEM;
> >>>>  			goto out;
> >>>>  		}
> >>>> +		arch_kexec_post_alloc_pages(page_address(page), 1, 0);
> >>>>  		ptr = kmap(page);
> >>>>  		ptr += maddr & ~PAGE_MASK;
> >>>>  		mchunk = min_t(size_t, mbytes,
> >>>> @@ -882,6 +893,7 @@ static int kimage_load_crash_segment(struct kimage *image,
> >>>>  			result = copy_from_user(ptr, buf, uchunk);
> >>>>  		kexec_flush_icache_page(page);
> >>>>  		kunmap(page);
> >>>> +		arch_kexec_pre_free_pages(page_address(page), 1);
> >>>>  		if (result) {
> >>>>  			result = -EFAULT;
> >>>>  			goto out;
> >>>> -- 
> >>>> 2.9.5
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> kexec mailing list
> >>>> kexec@lists.infradead.org
> >>>> http://lists.infradead.org/mailman/listinfo/kexec
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec