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

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Message-ID: <49706f0e-03b6-8c43-c35f-c0b0338a17bd@redhat.com>
Date:   Thu, 21 Jun 2018 21:27:23 +0800
From:   lijiang <lijiang@...hat.com>
To:     Baoquan He <bhe@...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

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

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