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Message-ID: <3885ab33-d704-4e50-bad7-0dbe3b012ebe@intel.com>
Date: Wed, 28 Feb 2024 12:16:11 +1300
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCHv8 09/17] x86/mm: Adding callbacks to prepare encrypted
 memory for kexec
Content-Language: en-US
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Thomas Gleixner
	<tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
	<bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, <x86@kernel.org>
CC: "Rafael J. Wysocki" <rafael@kernel.org>, Peter Zijlstra
	<peterz@infradead.org>, Adrian Hunter <adrian.hunter@intel.com>, "Kuppuswamy
 Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>, "Elena
 Reshetova" <elena.reshetova@intel.com>, Jun Nakajima
	<jun.nakajima@intel.com>, Rick Edgecombe <rick.p.edgecombe@intel.com>, Tom
 Lendacky <thomas.lendacky@amd.com>, "Kalra, Ashish" <ashish.kalra@amd.com>,
	"Sean Christopherson" <seanjc@google.com>, Baoquan He <bhe@redhat.com>,
	<kexec@lists.infradead.org>, <linux-coco@lists.linux.dev>,
	<linux-kernel@vger.kernel.org>, Nikolay Borisov <nik.borisov@suse.com>
References: <20240227212452.3228893-1-kirill.shutemov@linux.intel.com>
 <20240227212452.3228893-10-kirill.shutemov@linux.intel.com>
From: "Huang, Kai" <kai.huang@intel.com>
In-Reply-To: <20240227212452.3228893-10-kirill.shutemov@linux.intel.com>
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On 28/02/2024 10:24 am, Kirill A. Shutemov wrote:
> AMD SEV and Intel TDX guests allocate shared buffers for performing I/O.
> This is done by allocating pages normally from the buddy allocator and
> then converting them to shared using set_memory_decrypted().
> 
> On kexec, the second kernel is unaware of which memory has been
> converted in this manner. It only sees E820_TYPE_RAM. Accessing shared
> memory as private is fatal.
> 
> Therefore, the memory state must be reset to its original state before
> starting the new kernel with kexec.
> 
> The process of converting shared memory back to private occurs in two
> steps:
> 
> - enc_kexec_stop_conversion() stops new conversions.
> 
> - enc_kexec_unshare_mem() unshares all existing shared memory, reverting
>    it back to private.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>x
> ---

Reviewed-by: Kai Huang <kai.huang@intel.com>