Messages in this thread | | | From | Pavel Tatashin <> | Date | Mon, 15 Feb 2021 17:28:18 -0500 | Subject | Re: [PATCH v2 1/1] arm64: mm: correct the inside linear map boundaries during hotplug check |
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> > > > Btw, the KASLR check is incorrect: memstart_addr could also be > > negative when running the 52-bit VA kernel on hardware that is only > > 48-bit VA capable. > > Good point! > > if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) > memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52); > > So, I will remove IS_ENABLED(CONFIG_RANDOMIZE_BASE) again.
Hi Ard,
Actually, looking more at this, I do not see how with 52VA on a 48VA processor start offset can become negative unless randomization is involved. The start of the linear map will point to the first physical address that is reported by memblock_start_of_DRAM(). However, memstart_addr will be negative. So, I think the current approach using IS_ENABLED(CONFIG_RANDOMIZE_BASE) is good.
48VA processor with VA_BITS_48: memstart_addr 40000000 start_linear_pa 40000000 end_linear_pa 80003fffffff
48VA processor with VA_BITS_52: memstart_addr fff1000040000000 <- Negative start_linear_pa 40000000 <- positive, and the first PA address end_linear_pa 80003fffffff
Thank you, Pasha
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