linux-kernel - Re: [PATCH 2/4 V3] Allocate pages for kdump without encryption when SME is enabled

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Message-ID: <20180621102321.GK29979@MiWiFi-R3L-srv>
Date:   Thu, 21 Jun 2018 18:23:21 +0800
From:   Baoquan He <bhe@...hat.com>
To:     lijiang <lijiang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, thomas.lendacky@....com,
        iommu@...ts.linux-foundation.org, dyoung@...hat.com,
        kexec@...ts.infradead.org
Subject: Re: [PATCH 2/4 V3] Allocate pages for kdump without encryption when
 SME is enabled

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@...hat.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?

> 
> >> +		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@...ts.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/kexec

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