mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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44e92e0364
Currently, the nds32 FPU dose not support the arithmetic of denormalized
number. When the nds32 FPU finds the result of the instruction is a
denormlized number, the nds32 FPU considers it to be an underflow condition
and rounds the result to an appropriate number. It may causes some loss
of precision. This commit proposes a solution to re-execute the
instruction by the FPU emulator to enhance the precision. To transfer
calculations from user space to kernel space, this feature will enable
the underflow exception trap by default. Enabling this feature may cause
some side effects:
1. Performance loss due to extra FPU exception
2. Need another scheme to control real underflow trap
A new parameter, UDF_trap, which is belong to FPU context is used
to control underflow trap.
User can configure this feature via CONFIG_SUPPORT_DENORMAL_ARITHMETIC
Signed-off-by: Vincent Chen <vincentc@andestech.com>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
83 lines
1.7 KiB
C
83 lines
1.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2005-2017 Andes Technology Corporation
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#include <linux/syscalls.h>
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#include <linux/uaccess.h>
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#include <asm/cachectl.h>
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#include <asm/proc-fns.h>
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#include <asm/udftrap.h>
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#include <asm/fpu.h>
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SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
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unsigned long, prot, unsigned long, flags,
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unsigned long, fd, unsigned long, pgoff)
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{
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if (pgoff & (~PAGE_MASK >> 12))
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return -EINVAL;
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return sys_mmap_pgoff(addr, len, prot, flags, fd,
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pgoff >> (PAGE_SHIFT - 12));
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}
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SYSCALL_DEFINE4(fadvise64_64_wrapper,int, fd, int, advice, loff_t, offset,
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loff_t, len)
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{
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return sys_fadvise64_64(fd, offset, len, advice);
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}
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SYSCALL_DEFINE3(cacheflush, unsigned int, start, unsigned int, end, int, cache)
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{
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struct vm_area_struct *vma;
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bool flushi = true, wbd = true;
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vma = find_vma(current->mm, start);
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if (!vma)
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return -EFAULT;
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switch (cache) {
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case ICACHE:
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wbd = false;
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break;
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case DCACHE:
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flushi = false;
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break;
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case BCACHE:
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break;
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default:
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return -EINVAL;
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}
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cpu_cache_wbinval_range_check(vma, start, end, flushi, wbd);
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return 0;
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}
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SYSCALL_DEFINE1(udftrap, int, option)
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{
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#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
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int old_udftrap;
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if (!used_math()) {
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load_fpu(&init_fpuregs);
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current->thread.fpu.UDF_trap = init_fpuregs.UDF_trap;
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set_used_math();
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}
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old_udftrap = current->thread.fpu.UDF_trap;
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switch (option) {
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case DISABLE_UDFTRAP:
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current->thread.fpu.UDF_trap = 0;
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break;
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case ENABLE_UDFTRAP:
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current->thread.fpu.UDF_trap = FPCSR_mskUDFE;
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break;
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case GET_UDFTRAP:
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break;
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default:
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return -EINVAL;
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}
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return old_udftrap;
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#else
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return -ENOTSUPP;
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#endif
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}
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