linux-kernel - Re: [PATCH 1/5 V5] Add a function(ioremap_encrypted) for kdump when AMD sme enabled

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Date:   Tue, 3 Jul 2018 10:17:19 +0800
From:   lijiang <lijiang@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
        hpa@...or.com, ebiederm@...ssion.com, joro@...tes.org,
        thomas.lendacky@....com, dyoung@...hat.com,
        kexec@...ts.infradead.org, iommu@...ts.linux-foundation.org,
        bhe@...hat.com
Subject: Re: [PATCH 1/5 V5] Add a function(ioremap_encrypted) for kdump when
 AMD sme enabled

在 2018年07月02日 18:14, Borislav Petkov 写道:
> On Mon, Jul 02, 2018 at 03:26:35PM +0800, Lianbo Jiang wrote:
>> @@ -131,7 +132,8 @@ static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
>>   * caller shouldn't need to know that small detail.
>>   */
>>  static void __iomem *__ioremap_caller(resource_size_t phys_addr,
>> -		unsigned long size, enum page_cache_mode pcm, void *caller)
>> +		unsigned long size, enum page_cache_mode pcm,
>> +		void *caller, bool encrypted)
> 
> So instead of sprinkling that @encrypted argument everywhere and then
> setting it based on sme_active() ...
> 
>>  {
>>  	unsigned long offset, vaddr;
>>  	resource_size_t last_addr;
>> @@ -199,7 +201,7 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
>>  	 * resulting mapping.
>>  	 */
>>  	prot = PAGE_KERNEL_IO;
>> -	if (sev_active() && mem_flags.desc_other)
>> +	if ((sev_active() && mem_flags.desc_other) || encrypted)
> 
> ... why can't you simply do your checks:
> 
> 	sme_active() && is_kdump_kernel()
> 
> here so that __ioremap_caller() can automatically choose the proper
> pgprot value when ioremapping the memory in the kdump kernel?
> 
> And this way the callers don't even have to care whether the memory is
> encrypted or not?
> 
Thank you, Boris. I'm very glad to read your comments. That's a good idea, but it has some
unencrypted memory in kdump mode, for example, the elfcorehdr. In fact, the elfcorehdr and
notes call the same function(read_from_oldmem->ioremap_cache), in this case, it is very
difficult to properly remap the memory if the caller don't care whether the memory is encrypted.

Regards,
Lianbo
>>  		prot = pgprot_encrypted(prot);
>>  
>>  	switch (pcm) {
>