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Date: Tue, 4 Sep 2018 09:29:02 +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,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in
early_memremap_pgprot_adjust() to adjust encryption mask
On 09/04/18 at 08:44am, Dave Young wrote:
> 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?
The right way should be checking the efi mem types instead of only
checking is_kdump_kernel.
Something like below, probably also check the region size with something
like efi_mem_range_type(addr, size), return -EINVAL in case cross
different type efi memory desc, added efi people in cc:
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index c63a545ec199..4a24e138c0d0 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -527,6 +527,13 @@ static bool memremap_should_map_decrypted(resource_size_t phys_addr,
break;
}
+ if (is_kdump_kernel() {
+ switch (efi_mem_type(phys_addr)) {
+ /* refer to arch/x86/boot/compressed/eboot.c -> setup_e820()*/
+ case ...
+ }
+ }
+
return false;
}
>
> > >> + */
> > >> 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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