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Date: Tue, 4 Sep 2018 08:44:17 +0800
From: Dave Young <dyoung@...hat.com>
To: lijiang <lijiang@...hat.com>
Cc: linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
hpa@...or.com, ebiederm@...ssion.com, joro@...tes.org,
thomas.lendacky@....com, kexec@...ts.infradead.org,
iommu@...ts.linux-foundation.org, bhe@...hat.com
Subject: Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in
early_memremap_pgprot_adjust() to adjust encryption mask
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@...hat.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
> >
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