linux-kernel - Re: [PATCH v8 2/7] kexec: define functions to map and unmap segments

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Message-ID: <3723d5f8-12b7-417f-9030-218e561e9397@linux.microsoft.com>
Date: Fri, 21 Feb 2025 13:05:45 -0800
From: steven chen <chenste@...ux.microsoft.com>
To: Mimi Zohar <zohar@...ux.ibm.com>, stefanb@...ux.ibm.com,
 roberto.sassu@...weicloud.com, roberto.sassu@...wei.com,
 eric.snowberg@...cle.com, ebiederm@...ssion.com, paul@...l-moore.com,
 code@...icks.com, bauermann@...abnow.com, linux-integrity@...r.kernel.org,
 kexec@...ts.infradead.org, linux-security-module@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
 James.Bottomley@...senPartnership.com, bhe@...hat.com, vgoyal@...hat.com,
 dyoung@...hat.com
Subject: Re: [PATCH v8 2/7] kexec: define functions to map and unmap segments

On 2/20/2025 9:22 AM, Mimi Zohar wrote:
> Hi Steven,
>
> On Tue, 2025-02-18 at 14:54 -0800, steven chen wrote:
>> Currently, the mechanism to map and unmap segments to the kimage
>> structure is not available to the subsystems outside of kexec.  This
>> functionality is needed when IMA is allocating the memory segments
>> during kexec 'load' operation.  Implement functions to map and unmap
>> segments to kimage.
> Obviously up to now Kexec was mapping the segments. Missing from this patch description is
> the reason "why" these functions are needed now.  It's not enough to say "is needed when
> IMA is allocating the memory segments during kexec 'load' operation".  The question is why
> does "IMA" need to allocate the memory segments.  Don't make the kexec/kexec_dump
> maintainers guess.
>
> Refer to the section "Describe your changes" in
> https://www.kernel.org/doc/Documentation/process/submitting-patches.rst
>
>> Implement kimage_map_segment() to enable mapping of IMA buffer source
>> pages to the kimage structure post kexec 'load'.  This function,
>> accepting a kimage pointer, an address, and a size, will gather the
>> source pages within the specified address range, create an array of page
>> pointers, and map these to a contiguous virtual address range.  The
>> function returns the start of this range if successful, or NULL if
>> unsuccessful.
>>
>> Implement kimage_unmap_segment() for unmapping segments
>> using vunmap().
>>
>> From: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> Author: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
> Again, no such thing as an "Author" tag.  Refer to the comments on 1/7.
>
>> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
> As previously requested, please add the Cc's inline here and in all the kexec/kdump
> related patches:
>
> Cc: Eric Biederman <ebiederm@...ssion.com>
> Cc: Baoquan He <bhe@...hat.com>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: Dave Young <dyoung@...hat.com>
>
>> Signed-off-by: steven chen <chenste@...ux.microsoft.com>
> thanks,
>
> Mimi

Mimi, thanks. I will update in next version.

Steven