Hi,
On 8/22/20 3:44 AM, Gavin Shan wrote:
> Depending on the kernel configuration, PUD_SIZE could be equal to
> PMD_SIZE. For example, both of them are 512MB with the following
> kernel configuration. In this case, both PUD and PMD are folded
> to PGD.
>
> CONFIG_ARM64_64K_PAGES y
> CONFIG_ARM64_VA_BITS 42
> CONFIG_PGTABLE_LEVELS 2
>
> With the above configuration, the stage2 PUD is used to backup the
> 512MB huge page when the stage2 mapping is built. During the mapping,
> the PUD and its subordinate levels of page table entries are unmapped
> if the PUD is present and not huge page sensitive in stage2_set_pud_huge().
> Unfornately, the @addr isn't aligned to S2_PUD_SIZE and wrong page table
> entries are zapped. It eventually leads to PUD's present bit can't be
> cleared successfully and infinite loop in stage2_set_pud_huge().
>
> This fixes the issue by checking with S2_{PUD, PMD}_SIZE instead of
> {PUD, PMD}_SIZE to determine if stage2 PUD or PMD is used to back the
> huge page. For this particular case, the stage2 PMD entry should be
> used to backup the 512MB huge page with stage2_set_pmd_huge().
I can reproduce this on my rockpro64 using kvmtool.
I see two issues here: first, PUD_SIZE = 512MB, but S2_PUD_SIZE = 4TB (checked
using printk), and second, stage2_set_pud_huge() hangs. I'm working on debugging them.
Thanks,
Alex
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