Commits · 4a03b2ac06a5bcae29371866d9d11f5bfd4c9188 · Kirill Smelkov / linux

12 Oct, 2022 19 commits

Youling Tang authored Oct 12, 2022

Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to
the LoongArch architecture, so as to add support for the kexec re-boot
mechanism (CONFIG_KEXEC) on LoongArch platforms.

Kexec supports loading vmlinux.elf in ELF format and vmlinux.efi in PE
format.

I tested kexec on LoongArch machines (Loongson-3A5000) and it works as
expected:

 $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
 $ sudo kexec -e
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

4a03b2ac

LoongArch: Use generic BUG() handler · 2d2c3952

Youling Tang authored Oct 12, 2022

Inspired by commit 9fb7410f("arm64/BUG: Use BRK instruction for
generic BUG traps"), do similar for LoongArch to use generic BUG()
handler.

This patch uses the BREAK software breakpoint instruction to generate
a trap instead, similarly to most other arches, with the generic BUG
code generating the dmesg boilerplate.

This allows bug metadata to be moved to a separate table and reduces
the amount of inline code at BUG() and WARN() sites. This also avoids
clobbering any registers before they can be dumped.

To mitigate the size of the bug table further, this patch makes use of
the existing infrastructure for encoding addresses within the bug table
as 32-bit relative pointers instead of absolute pointers.

(Note: this limits the max kernel size to 2GB.)

Before patch:
[ 3018.338013] lkdtm: Performing direct entry BUG
[ 3018.342445] Kernel bug detected[#5]:
[ 3018.345992] CPU: 2 PID: 865 Comm: cat Tainted: G D 6.0.0-rc6+ #35

After patch:
[  125.585985] lkdtm: Performing direct entry BUG
[  125.590433] ------------[ cut here ]------------
[  125.595020] kernel BUG at drivers/misc/lkdtm/bugs.c:78!
[  125.600211] Oops - BUG[#1]:
[  125.602980] CPU: 3 PID: 410 Comm: cat Not tainted 6.0.0-rc6+ #36

Out-of-line file/line data information obtained compared to before.
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

2d2c3952

LoongArch: Add SysRq-x (TLB Dump) support · dea2df3c

Huacai Chen authored Oct 12, 2022

Add SysRq-x (TLB Dump) support for LoongArch, which is useful for
debugging.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

dea2df3c

LoongArch: Add perf events support · b37042b2

Huacai Chen authored Oct 12, 2022

The perf events infrastructure of LoongArch is very similar to old MIPS-
based Loongson, so most of the codes are derived from MIPS.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

b37042b2

LoongArch: Add qspinlock support · 5f1e001b

Huacai Chen authored Oct 12, 2022

On NUMA system, the performance of qspinlock is better than generic
spinlock. Below is the UnixBench test results on a 8 nodes (4 cores
per node, 32 cores in total) machine.

A. With generic spinlock:

System Benchmarks Index Values               BASELINE       RESULT    INDEX
Dhrystone 2 using register variables         116700.0  449574022.5  38523.9
Double-Precision Whetstone                       55.0      85190.4  15489.2
Execl Throughput                                 43.0      14696.2   3417.7
File Copy 1024 bufsize 2000 maxblocks          3960.0     143157.8    361.5
File Copy 256 bufsize 500 maxblocks            1655.0      37631.8    227.4
File Copy 4096 bufsize 8000 maxblocks          5800.0     444814.2    766.9
Pipe Throughput                               12440.0    5047490.7   4057.5
Pipe-based Context Switching                   4000.0    2021545.7   5053.9
Process Creation                                126.0      23829.8   1891.3
Shell Scripts (1 concurrent)                     42.4      33756.7   7961.5
Shell Scripts (8 concurrent)                      6.0       4062.9   6771.5
System Call Overhead                          15000.0    2479748.6   1653.2
                                                                   ========
System Benchmarks Index Score                                        2955.6

B. With qspinlock:

System Benchmarks Index Values               BASELINE       RESULT    INDEX
Dhrystone 2 using register variables         116700.0  449467876.9  38514.8
Double-Precision Whetstone                       55.0      85174.6  15486.3
Execl Throughput                                 43.0      14769.1   3434.7
File Copy 1024 bufsize 2000 maxblocks          3960.0     146150.5    369.1
File Copy 256 bufsize 500 maxblocks            1655.0      37496.8    226.6
File Copy 4096 bufsize 8000 maxblocks          5800.0     447527.0    771.6
Pipe Throughput                               12440.0    5175989.2   4160.8
Pipe-based Context Switching                   4000.0    2207747.8   5519.4
Process Creation                                126.0      25125.5   1994.1
Shell Scripts (1 concurrent)                     42.4      33461.2   7891.8
Shell Scripts (8 concurrent)                      6.0       4024.7   6707.8
System Call Overhead                          15000.0    2917278.6   1944.9
                                                                   ========
System Benchmarks Index Score                                        3040.1
Signed-off-by: Rui Wang <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

5f1e001b

LoongArch: Use TLB for ioremap() · d2791341

Huacai Chen authored Oct 12, 2022

We can support more cache attributes (e.g., CC, SUC and WUC) and page
protection when we use TLB for ioremap(). The implementation is based
on GENERIC_IOREMAP.

The existing simple ioremap() implementation has better performance so
we keep it and introduce ARCH_IOREMAP to control the selection.

We move pagetable_init() earlier to make early ioremap() works, and we
modify the PCI ecam mapping because the TLB-based version of ioremap()
will actually take the size into account.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

d2791341

LoongArch: Support access filter to /dev/mem interface · 235d074f

Huacai Chen authored Oct 12, 2022

Accidental access to /dev/mem is obviously disastrous, but specific
access can be used by people debugging the kernel. So select GENERIC_
LIB_DEVMEM_IS_ALLOWED, as well as define ARCH_HAS_VALID_PHYS_ADDR_RANGE
and related helpers, to support access filter to /dev/mem interface.
Signed-off-by: Weihao Li <liweihao@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

235d074f

LoongArch: Refactor cache probe and flush methods · b61a40af

Huacai Chen authored Oct 12, 2022

Current cache probe and flush methods have some drawbacks:
1, Assume there are 3 cache levels and only 3 levels;
2, Assume L1 = I + D, L2 = V, L3 = S, V is exclusive, S is inclusive.

However, the fact is I + D, I + D + V, I + D + S and I + D + V + S are
all valid. So, refactor the cache probe and flush methods to adapt more
types of cache hierarchy.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

b61a40af

LoongArch: mm: Refactor TLB exception handlers · a2a84e36

Rui Wang authored Oct 12, 2022

This patch simplifies TLB load, store and modify exception handlers:

1. Reduce instructions, such as alu/csr and memory access;
2. Execute tlb search instruction only in the fast path;
3. Return directly from the fast path for both normal and huge pages;
4. Re-tab the assembly for better vertical alignment.

And fixes the concurrent modification issue of fast path for huge pages.

This issue will occur in the following steps:

   CPU-1 (In TLB exception)         CPU-2 (In THP splitting)
1: Load PMD entry (HUGE=1)
2: Goto huge path
3:                                  Store PMD entry (HUGE=0)
4: Reload PMD entry (HUGE=0)
5: Fill TLB entry (PA is incorrect)

This patch also slightly improves the TLB processing performance:

* Normal pages: 2.15%, Huge pages: 1.70%.

  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <sys/mman.h>

  int main(int argc, char *argv[])
  {
        size_t page_size;
        size_t mem_size;
        size_t off;
        void *base;
        int flags;
        int i;

        if (argc < 2) {
                fprintf(stderr, "%s MEM_SIZE [HUGE]\n", argv[0]);
                return -1;
        }

        page_size = sysconf(_SC_PAGESIZE);
        flags = MAP_PRIVATE | MAP_ANONYMOUS;
        mem_size = strtoul(argv[1], NULL, 10);
        if (argc > 2)
                flags |= MAP_HUGETLB;

        for (i = 0; i < 10; i++) {
                base = mmap(NULL, mem_size, PROT_READ, flags, -1, 0);
                if (base == MAP_FAILED) {
                        fprintf(stderr, "Map memory failed!\n");
                        return -1;
                }

                for (off = 0; off < mem_size; off += page_size)
                        *(volatile int *)(base + off);

                munmap(base, mem_size);
        }

        return 0;
  }
Signed-off-by: Rui Wang <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

a2a84e36