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restore demand paging PR + PC fixes #31564

Merged
merged 42 commits into from
Jan 24, 2021
Merged

restore demand paging PR + PC fixes #31564

merged 42 commits into from
Jan 24, 2021

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andrewboie
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This PR:

  • Restores all the demand paging commits that were reverted on Friday (the root cause of the sentinel failure is DTS device dependency is shifting memory addresses between builds #31546)
  • Adds CONFIG_ARCH_MAPS_ALL_RAM. This signals to the kernel that all RAM has a bootup mapping, and not just the Zephyr image. Page frame management is unaffected, but this will be taken into account when establishing new memory mappings, as to not disturb the existing mapping for all RAM.
  • Enable CONFIG_ARCH_MAPS_ALL_RAM for ACPI targets. Various PC-like targets had their VM size increased.

@github-actions github-actions bot added area: API Changes to public APIs area: ARM ARM (32-bit) Architecture area: ARM_64 area: Boards area: Devicetree area: X86 x86 Architecture (32-bit) labels Jan 23, 2021
@andrewboie andrewboie force-pushed the demand-paging2 branch 3 times, most recently from 8da8e1b to e796dc2 Compare January 23, 2021 22:59
Andrew Boie added 11 commits January 23, 2021 15:01
arch: add KERNEL_VM_OFFSET
e1a6394 
This is only needed if the base address of SRAM doesn't
have the same alignment as the base address of the virtual
address space.

Fix the calculations on X86 where this is the case.

Signed-off-by: Andrew Boie <[email protected]>
linker-defs: add syms for kernel image bounds
e2ec646 
These are needed on MMU systems and define where the kernel
image resides in virtual memory at boot so that it may be
memory-mapped.

Signed-off-by: Andrew Boie <[email protected]>
x86: linker: define z_mapped_* symbols
ce23cff 
We will use this to map the kernel instead of all RAM.
The end of the kernel is always page-aligned, regardless
of CONFIG_SRAM_REGION_PERMISSIONS as it must be mapped.

Signed-off-by: Andrew Boie <[email protected]>
arm64: linker: define z_mapped_* symbols
96cb7e7 
Add linker symbols corresponding to the start and end of the
mapped Zephyr image. This is not used by the ARM arch yet, but
is required to compile the core kernel MMU code.

Signed-off-by: Andrew Boie <[email protected]>
tests: x86: pagetables: pass if userspace disabled
266d584 
_app_smem doesn't exist in this case.

Signed-off-by: Andrew Boie <[email protected]>
kernel: add CONFIG_ARCH_HAS_RESERVED_PAGE_FRAMES
7f7f038 
We will need this to run on x86 with PC-like hardware.

Signed-off-by: Andrew Boie <[email protected]>
kernel: add page frame management
7fb757e 
Initialize the page frame ontology at boot and update it
when we do memory mappings.

Signed-off-by: Andrew Boie <[email protected]>
kernel: add k_mem_map() interface
164edf5 
Allows applications to increase the data space available to Zephyr
via anonymous memory mappings. Loosely based on mmap().

Signed-off-by: Andrew Boie <[email protected]>
mmu: add k_mem_free_get()
cb1d1ae 
Return the amount of physical anonymous memory remaining.

Signed-off-by: Andrew Boie <[email protected]>
x86: reserve the first megabyte
6a24a8f 
A more comprehensive solution would use E820 enumeration, but we
are unlikely to ever care that much, as we intend to use demand
paging on microcontrollers and not PC-like hardware. This is
really to just prevent QEMU from crashing.

Signed-off-by: Andrew Boie <[email protected]>
x86: tests: pagetables: fix assumptions
483da8e 
All RAM may not be mapped. Check the mapping for the main kernel
image and the locore if it exists.

Signed-off-by: Andrew Boie <[email protected]>
Andrew Boie added 18 commits January 23, 2021 15:01
kernel: add demand paging implementation
d62577e 
Implement runtime APIs for pinning, paging in, and evicting
memory, as well as the page fault hook called from architecture
code.

Signed-off-by: Andrew Boie <[email protected]>
tests: mem_map: pin test pages
f19583e 
These get mapped to multiple virtual addresses and must be
pinned.

Signed-off-by: Andrew Boie <[email protected]>
demand_paging: add NRU algorithm
9423c13 
Simple textbook Not Recently Used eviction algorithm.

Signed-off-by: Andrew Boie <[email protected]>
demand_paging: add RAM-based demo backing store
a3d6438 
Will be used by QEMU targets for testing purposes.

Signed-off-by: Andrew Boie <[email protected]>
x86: implement demand paging APIs
4b21090 
All arch_ APIs and macros are implemented, and the page fault
handling code will call into the core kernel.

Signed-off-by: Andrew Boie <[email protected]>
qemu_x86_tiny: enable demand paging
fb96aa9 
This target is specifically for simulating x86 micro-
controllers with limited memory.

Signed-off-by: Andrew Boie <[email protected]>
mmu: pin the whole kernel
6a4e7c5 
This will enable testing of the implementation until the
critical set of pages is identified and known to the
kernel.

Signed-off-by: Andrew Boie <[email protected]>
tests: add basic k_mem_map() test
a6022ce 
Show we can measure free memory properly and map a page of
anonymous memory, which has been zeroed and is writable.

Signed-off-by: Andrew Boie <[email protected]>
tests: add intial demand paging testcase
bdf5c8b 
More to be added, but for now show that we can map more
anonymous memory than we physically have, and that reading/
writing to it works as expected.

Signed-off-by: Andrew Boie <[email protected]>
CODEOWNERS: add demand paging subdir
324bab1 
Adding myself as original author.

Signed-off-by: Andrew Boie <[email protected]>
kernel: add z_num_pagefaults_get()
3061d2e 
Simple counter of number of successfully handled page faults by
the core kernel.

Signed-off-by: Andrew Boie <[email protected]>
tests: demand_paging: add more API tests
b2e3e83 
Add remaining APIs in mem_manage.h even though not all have
been promoted to public (yet).

Signed-off-by: Andrew Boie <[email protected]>
mmu: backing stores reserve page fault room
8667075 
If we evict enough pages to completely fill the backing store,
through APIs like k_mem_map(), z_page_frame_evict(), or
z_mem_page_out(), this will produce a crash the next time we
try to handle a page fault.

The backing store now always reserves a free storage location
for actual page faults.

Signed-off-by: Andrew Boie <[email protected]>
tests: context: disable if DEMAND_PAGING
d612aa9 
Until zephyrproject-rtos#31333 is resolved, the periodic timer in the eviction
algorithm interacts with this test in such a way that the system
deadlocks.

Signed-off-by: Andrew Boie <[email protected]>
mmu: promote public APIs
da03a84 
These are application facing and are prefixed with k_.

Signed-off-by: Andrew Boie <[email protected]>
kernel: add CONFIG_ARCH_MAPS_ALL_RAM
05b8a42 
Some arches like x86 need all memory mapped so that they can
fetch information placed arbitrarily by firmware, like ACPI
tables.

Ensure that if this is the case, the kernel won't accidentally
clobber it by thinking the relevant virtual memory is unused.
Otherwise this has no effect on page frame management.

Signed-off-by: Andrew Boie <[email protected]>
boards: x86: increase VM size on PC-like
481bed3 
These are all PC systems which have large amounts of memory
which needs to be mapped at runtime (most are 2GB).

Increase the address space size accordingly, adding an extra
8MB for mappings.

The ACRN target has 8MB, give it 16MB of VM.

Signed-off-by: Andrew Boie <[email protected]>
x86: map all RAM if ACPI
9cc440e 
ACPI tables can lurk anywhere. Map all memory so they can be
read.

Signed-off-by: Andrew Boie <[email protected]>
@jenmwms
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jenmwms commented Jan 23, 2021

Thanks @andrewboie! I've started HW testing, will post details soon.

@andrewboie andrewboie requested a review from dcpleung January 23, 2021 23:33
@nashif nashif merged commit 7786103 into zephyrproject-rtos:master Jan 24, 2021
@jhedberg
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This unfortunately breaks EHL booting with SBL. Reverting to commit 3746ebc (i.e. right before this PR went in) makes it work again.

@jhedberg
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This unfortunately breaks EHL booting with SBL. Reverting to commit 3746ebc (i.e. right before this PR went in) makes it work again.

Using git bisect to narrow this down gives the following:

5c47bbc5010d98c6f6d795aa6d268138c3463bbd is the first bad commit
commit 5c47bbc5010d98c6f6d795aa6d268138c3463bbd
Author: Andrew Boie <[email protected]>
Date:   Thu Dec 10 11:23:21 2020 -0800

    x86: only map the kernel image
    
    The policy is changed and we no longer map all page frames.
    
    Signed-off-by: Andrew Boie <[email protected]>

 arch/x86/gen_mmu.py | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

@jhedberg
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jhedberg commented Jan 24, 2021 •
edited
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(edited - I was mixing 2MB and 2GB)

I added some debug logs to the ACPI table code with the suspicion that something is outside of the mapped region, but it looks to me like everything is still within 2GB that's declared for the board:

Starting MB Kernel ...
find_rsdp search 0xf0e0
find_rsdp rsdp 0xfff80
z_acpi_find_table rsdt 0x78854030
z_acpi_find_table returning sdt 0x788545b0
*** Booting Zephyr OS build zephyr-v2.4.0-3554-g3746ebc305f5  ***
z_acpi_find_table rsdt 0x78854030
z_acpi_find_table returning sdt 0x78854530
Hello World! ehl_crb_sbl

Btw, I seem to be unable to increase the declared RAM amount from 2GB (even if I also increase KERNEL_VM_SIZE) - it results in some build errors.

@dcpleung dcpleung mentioned this pull request Jan 25, 2021
Closed
@jhedberg jhedberg mentioned this pull request Jan 26, 2021
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@jenmwms jenmwms jenmwms approved these changes

@aasthagr aasthagr aasthagr approved these changes

@dcpleung dcpleung dcpleung approved these changes

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@andrewboie @jenmwms @jhedberg @dcpleung @aasthagr @nashif