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Date:   Tue, 4 Sep 2018 08:44:17 +0800
From:   Dave Young <dyoung@redhat.com>
To:     lijiang <lijiang@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
Subject: Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in
 early_memremap_pgprot_adjust() to adjust encryption mask
Message-ID: <20180904004417.GA9842@dhcp-128-65.nay.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>
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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?

> >> +                 */
> >>  		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
> >