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Subject: Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in
 early_memremap_pgprot_adjust() to adjust encryption mask
To:     Dave Young <dyoung@redhat.com>
Cc:     linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de,
        hpa@zytor.com, ebiederm@xmission.com, joro@8bytes.org,
        thomas.lendacky@amd.com, kexec@lists.infradead.org,
        iommu@lists.linux-foundation.org, bhe@redhat.com
References: <20180831081930.31561-1-lijiang@redhat.com>
 <20180831081930.31561-3-lijiang@redhat.com>
 <20180903024512.GA2568@dhcp-128-65.nay.redhat.com>
 <d2229538-51d5-ead7-c7e5-f4afe5b53693@redhat.com>
 <20180904004417.GA9842@dhcp-128-65.nay.redhat.com>
From:   lijiang <lijiang@redhat.com>
Message-ID: <da473e45-6790-89fb-42c8-9f8f38eb0cbf@redhat.com>
Date:   Tue, 4 Sep 2018 09:44:18 +0800
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在 2018年09月04日 08:44, Dave Young 写道:
> On 09/03/18 at 10:06pm, lijiang wrote:
>> 在 2018年09月03日 10:45, Dave Young 写道:
>>> On 08/31/18 at 04:19pm, Lianbo Jiang wrote:
>>>> For kdump kernel, when SME is enabled, the acpi table and dmi table will need
>>>> to be remapped without the memory encryption mask. So we have to strengthen
>>>> the logic in early_memremap_pgprot_adjust(), which makes us have an opportunity
>>>> to adjust the memory encryption mask.
>>>>
>>>> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
>>>> ---
>>>>  arch/x86/mm/ioremap.c | 9 ++++++++-
>>>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
>>>> index e01e6c695add..f9d9a39955f3 100644
>>>> --- a/arch/x86/mm/ioremap.c
>>>> +++ b/arch/x86/mm/ioremap.c
>>>> @@ -689,8 +689,15 @@ pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
>>>>  	encrypted_prot = true;
>>>>  
>>>>  	if (sme_active()) {
>>>> +                /*
>>>> +                 * In kdump kernel, the acpi table and dmi table will need
>>>> +                 * to be remapped without the memory encryption mask. Here
>>>> +                 * we have to strengthen the logic to adjust the memory
>>>> +                 * encryption mask.
>>>
>>> Assume the acpi/dmi tables are identical for both 1st kernel and kdump
>>> kernel, I'm not sure what is the difference, why need special handling
>>> for kdump. Can you add more explanations?
>>>
>>
>> Ok, i will use a dmi example to explain this issue.
>>
>> There are significant differences about E820 between the 1st kernel and kdump kernel. I pasted them at bottom.
>>
>> Firstly, we need to know how they are called.
>> __acpi_map_table()\                                                        / early_memremap_is_setup_data()
>>                    |-> early_memremap()-> early_memremap_pgprot_adjust()-> | memremap_is_efi_data()
>>  dmi_early_remap()/                                                        \ memremap_should_map_decrypted()-> e820__get_entry_type()
>>
>> Secondly, we also need to understand the memremap_should_map_decrypted(), which is illustrated by the fake code.
>> static bool memremap_should_map_decrypted(resource_size_t phys_addr,
>>                                           unsigned long size)
>> {
>>
>>     /* code ... */
>>
>>     switch (e820__get_entry_type(phys_addr, phys_addr + size - 1)) {
>>         case E820_TYPE_RESERVED:
>>         case E820_TYPE_ACPI:
>>         case E820_TYPE_NVS:
>>         case E820_TYPE_UNUSABLE:
>>                 /* For SEV, these areas are encrypted */
>>                 if (sev_active())
>>                         break;
>>                 /* Fallthrough */
>>
>>         case E820_TYPE_PRAM:
>>                 /* For SME, these areas are decrypted */
>>                 return true;
>>         default:
>>                 /* these areas are encrypted by default*/
>>                 break;
>>     }
>>
>>     return false;
>> }
>>
>> For the dmi case, the dmi base address is 0x6286b000 in my test machine.
>>
>> In the 1st kernel, the e820__get_entry_type() can get a valid entry and type by the dmi address, and we can also find the dmi base address from e820.
>> (see the 1st kernel log)
>> 0x6286b000 ∈ [mem 0x000000006286b000-0x000000006286efff]
>> So, these areas are decrypted according to the memremap_should_map_decrypted().
>>
>> In kdump kernel, the dmi base address is still 0x6286b000, but we can not find the dmi base address from e820 any more. The e820__get_entry_type() can
>> not get a valid entry and type by the dmi base address, it will go into the default branch. That is to say, these areas become encrypted. In fact, these
>> areas are also decrypted, so we have to strengthen the logic of adjusting the memory encryption mask.
>>
>>
>> The 1st kernel log:
>>
>> [    0.000000] BIOS-provided physical RAM map:
>> [    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000008bfff] usable
>> [    0.000000] BIOS-e820: [mem 0x000000000008c000-0x000000000009ffff] reserved
>> [    0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
>> [    0.000000] BIOS-e820: [mem 0x0000000000100000-0x0000000029920fff] usable
>> [    0.000000] BIOS-e820: [mem 0x0000000029921000-0x0000000029921fff] reserved
>> [    0.000000] BIOS-e820: [mem 0x0000000029922000-0x0000000062256fff] usable
>> [    0.000000] BIOS-e820: [mem 0x0000000062257000-0x0000000062356fff] reserved
>> [    0.000000] BIOS-e820: [mem 0x0000000062357000-0x000000006235cfff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x000000006235d000-0x00000000623dbfff] usable
>> [    0.000000] BIOS-e820: [mem 0x00000000623dc000-0x000000006261bfff] reserved
>> [    0.000000] BIOS-e820: [mem 0x000000006261c000-0x000000006263dfff] usable
>> [    0.000000] BIOS-e820: [mem 0x000000006263e000-0x000000006269dfff] reserved
>> [    0.000000] BIOS-e820: [mem 0x000000006269e000-0x00000000627d6fff] usable
>> [    0.000000] BIOS-e820: [mem 0x00000000627d7000-0x00000000627e3fff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x00000000627e4000-0x00000000627e4fff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x00000000627e5000-0x00000000627e8fff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x00000000627e9000-0x00000000627eafff] usable
>> [    0.000000] BIOS-e820: [mem 0x00000000627eb000-0x00000000627ebfff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x00000000627ec000-0x000000006286afff] usable
>> [    0.000000] BIOS-e820: [mem 0x000000006286b000-0x000000006286efff] reserved
>> [    0.000000] BIOS-e820: [mem 0x000000006286f000-0x00000000682f8fff] usable
>> [    0.000000] BIOS-e820: [mem 0x00000000682f9000-0x0000000068b05fff] reserved
>> [    0.000000] BIOS-e820: [mem 0x0000000068b06000-0x0000000068b09fff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x0000000068b0a000-0x0000000068b1afff] reserved
>> [    0.000000] BIOS-e820: [mem 0x0000000068b1b000-0x0000000068b1dfff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x0000000068b1e000-0x0000000071d1dfff] usable
>> [    0.000000] BIOS-e820: [mem 0x0000000071d1e000-0x0000000071d2dfff] reserved
>> [    0.000000] BIOS-e820: [mem 0x0000000071d2e000-0x0000000071d3dfff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x0000000071d3e000-0x0000000071d4dfff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x0000000071d4e000-0x0000000077ffffff] usable
>> [    0.000000] BIOS-e820: [mem 0x0000000078000000-0x000000008fffffff] reserved
>> [    0.000000] BIOS-e820: [mem 0x00000000fed80000-0x00000000fed80fff] reserved
>> [    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000087effffff] usable
>> [    0.000000] BIOS-e820: [mem 0x000000087f000000-0x000000087fffffff] reserved
>>
>> The kdump kernel log:
>>
>> [    0.000000] BIOS-provided physical RAM map:
>> [    0.000000] BIOS-e820: [mem 0x0000000000001000-0x000000000008bfff] usable
>> [    0.000000] BIOS-e820: [mem 0x0000000052000000-0x0000000061ffffff] usable
>> [    0.000000] BIOS-e820: [mem 0x00000000622ee000-0x0000000062300fff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x0000000062301000-0x0000000062301fff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x0000000062703000-0x0000000062703fff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x0000000062735000-0x0000000062737fff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x000000006273a000-0x000000006273afff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x0000000068b06000-0x0000000068b09fff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x0000000068b1b000-0x0000000068b1dfff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x0000000071d2e000-0x0000000071d3dfff] ACPI NVS
>> [    0.000000] BIOS-e820: [mem 0x0000000071d3e000-0x0000000071d4dfff] ACPI data
>> [    0.000000] BIOS-e820: [mem 0x00000007fe000000-0x000000087df70fff] usable
>>
> 
> Can you provide the efi memmap dmesg?  boot with efi=debug?
> 

Sorry, this machine is ProLiant DL385Gen10, which is not EFI boot.
I might not be able to provide the EFI information.

>>>> +                 */
>>>>  		if (early_memremap_is_setup_data(phys_addr, size) ||
>>>> -		    memremap_is_efi_data(phys_addr, size))
>>>> +		    memremap_is_efi_data(phys_addr, size) ||
>>>> +		    is_kdump_kernel())
>>>>  			encrypted_prot = false;
>>>>  	}
>>>>  
>>>> -- 
>>>> 2.17.1
>>>>
>>>
>>> Thanks
>>> Dave
>>>