Re: [PATCH v4 4/7] crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging

From: Baoquan He <bhe@redhat.com>
To: Coiby Xu <coxu@redhat.com>
Cc: kexec@lists.infradead.org, "Ondrej Kozina" <okozina@redhat.com>,
	"Milan Broz" <gmazyland@gmail.com>,
	"Thomas Staudt" <tstaudt@de.ibm.com>,
	"Daniel P . Berrangé" <berrange@redhat.com>,
	"Kairui Song" <ryncsn@gmail.com>,
	"Jan Pazdziora" <jpazdziora@redhat.com>,
	"Pingfan Liu" <kernelfans@gmail.com>,
	"Dave Young" <dyoung@redhat.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	"Dave Hansen" <dave.hansen@intel.com>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Vivek Goyal" <vgoyal@redhat.com>
Subject: Re: [PATCH v4 4/7] crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging
Date: Tue, 4 Jun 2024 21:52:56 +0800	[thread overview]
Message-ID: <Zl8cOOv9gVzdkU0f@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20240523050451.788754-5-coxu@redhat.com>

On 05/23/24 at 01:04pm, Coiby Xu wrote:
> When there is CPU/memory hot-plugging, the kdump kernel image and initrd
> will be reloaded. The user space can write the "reuse" command to
> /sys/kernel/crash_dm_crypt_key so the stored keys can be re-saved again.
> 
> Note currently only x86 (commit ea53ad9cf73b ("x86/crash: add x86 crash
> hotplug support")) and ppc (WIP) supports the new infrastructure
> (commit 247262756121 ("crash: add generic infrastructure for crash
> hotplug support")). If the new infrastructure get extended to all arches,
> this patch can be dropped.

I am confused, what is the new infrastructure? And why this patch can be
dropped if 'the new infrastructure' is extended to all arches.

> 
> Signed-off-by: Coiby Xu <coxu@redhat.com>
> ---
>  kernel/crash_dump_dm_crypt.c | 30 ++++++++++++++++++++++++++----
>  1 file changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
> index 89fec768fba8..b4dc881cc867 100644
> --- a/kernel/crash_dump_dm_crypt.c
> +++ b/kernel/crash_dump_dm_crypt.c
> @@ -10,12 +10,13 @@
>  // The key scription has the format: cryptsetup:UUID 11+36+1(NULL)=48
>  #define KEY_DESC_LEN 48
>  
> -static char *STATE_STR[] = {"fresh", "initialized", "recorded", "loaded"};
> +static char *STATE_STR[] = {"fresh", "initialized", "recorded", "loaded", "reuse"};
>  static enum STATE_ENUM {
>  	FRESH = 0,
>  	INITIALIZED,
>  	RECORDED,
>  	LOADED,
> +	REUSE,
>  } state;
>  
>  static unsigned int key_count;
> @@ -90,12 +91,31 @@ static int record_key_desc(const char *buf, struct dm_crypt_key *dm_key)
>  	return 0;
>  }
>  
> +static void get_keys_from_kdump_reserved_memory(void)
> +{
> +	struct keys_header *keys_header_loaded;
> +
> +	arch_kexec_unprotect_crashkres();
> +
> +	keys_header_loaded = kmap_local_page(pfn_to_page(
> +		kexec_crash_image->dm_crypt_keys_addr >> PAGE_SHIFT));
> +
> +	memcpy(keys_header, keys_header_loaded, keys_header_size);
> +	kunmap_local(keys_header_loaded);
> +	state = RECORDED;
> +}
> +
>  static int process_cmd(const char *buf, size_t count)
>  {
>  	if (strncmp(buf, "init ", 5) == 0)
>  		return init(buf);
>  	else if (strncmp(buf, "record ", 7) == 0)
>  		return record_key_desc(buf, &keys_header->keys[key_count]);
> +	else if (!strcmp(buf, "reuse")) {
> +		state = REUSE;
> +		get_keys_from_kdump_reserved_memory();
> +		return 0;
> +	}
>  
>  	return -EINVAL;
>  }
> @@ -175,9 +195,11 @@ int crash_load_dm_crypt_keys(struct kimage *image)
>  	}
>  
>  	image->dm_crypt_keys_addr = 0;
> -	r = build_keys_header();
> -	if (r)
> -		return r;
> +	if (state != REUSE) {
> +		r = build_keys_header();
> +		if (r)
> +			return r;

Is the logic here wrong? Isn't it we return when it's REUSE. If not
REUSE, we need build_keys_header(), then add buffer?

> +	}
>  
>  	kbuf.buffer = keys_header;
>  	kbuf.bufsz = keys_header_size;
> -- 
> 2.45.0
> 

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