[PATCH v3 4/4] riscv: Stop emitting preventive sfence.vma for new userspace mappings with Svvptc

[kernel test robot]

Hi Alexandre,

kernel test robot noticed the following build errors:

[auto build test ERROR on robh/for-next]
[also build test ERROR on linus/master v6.10-rc7]
[cannot apply to next-20240710]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexandre-Ghiti/riscv-Add-ISA-extension-parsing-for-Svvptc/20240702-171920
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
patch link:    https://lore.kernel.org/r/20240702085034.48395-5-alexghiti%40rivosinc.com
patch subject: [PATCH v3 4/4] riscv: Stop emitting preventive sfence.vma for new userspace mappings with Svvptc
config: riscv-allmodconfig (https://download.01.org/0day-ci/archive/20240711/202407111151.m5cK0E6R-lkp@intel.com/config)
compiler: clang version 19.0.0git (https://github.com/llvm/llvm-project a0c6b8aef853eedaa0980f07c0a502a5a8a9740e)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240711/202407111151.m5cK0E6R-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202407111151.m5cK0E6R-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from lib/test_bitops.c:10:
   In file included from include/linux/module.h:19:
   In file included from include/linux/elf.h:6:
   In file included from arch/riscv/include/asm/elf.h:12:
   In file included from include/linux/compat.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:9:
   In file included from include/linux/sched/task.h:13:
   In file included from include/linux/uaccess.h:11:
   In file included from arch/riscv/include/asm/uaccess.h:12:
>> arch/riscv/include/asm/pgtable.h:498:1: error: label at end of compound statement is a C23 extension [-Werror,-Wc23-extensions]
     498 | }
         | ^
   1 error generated.


vim +498 arch/riscv/include/asm/pgtable.h

07037db5d479f9 Palmer Dabbelt          2017-07-10  469  
07037db5d479f9 Palmer Dabbelt          2017-07-10  470  #define pgd_ERROR(e) \
07037db5d479f9 Palmer Dabbelt          2017-07-10  471  	pr_err("%s:%d: bad pgd " PTE_FMT ".\n", __FILE__, __LINE__, pgd_val(e))
07037db5d479f9 Palmer Dabbelt          2017-07-10  472  
07037db5d479f9 Palmer Dabbelt          2017-07-10  473  
07037db5d479f9 Palmer Dabbelt          2017-07-10  474  /* Commit new configuration to MMU hardware */
864609c6a0b5f0 Matthew Wilcox (Oracle  2023-08-02  475) static inline void update_mmu_cache_range(struct vm_fault *vmf,
864609c6a0b5f0 Matthew Wilcox (Oracle  2023-08-02  476) 		struct vm_area_struct *vma, unsigned long address,
864609c6a0b5f0 Matthew Wilcox (Oracle  2023-08-02  477) 		pte_t *ptep, unsigned int nr)
07037db5d479f9 Palmer Dabbelt          2017-07-10  478  {
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  479  	asm goto(ALTERNATIVE("nop", "j %l[svvptc]", 0, RISCV_ISA_EXT_SVVPTC, 1)
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  480  		 : : : : svvptc);
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  481  
07037db5d479f9 Palmer Dabbelt          2017-07-10  482  	/*
07037db5d479f9 Palmer Dabbelt          2017-07-10  483  	 * The kernel assumes that TLBs don't cache invalid entries, but
07037db5d479f9 Palmer Dabbelt          2017-07-10  484  	 * in RISC-V, SFENCE.VMA specifies an ordering constraint, not a
07037db5d479f9 Palmer Dabbelt          2017-07-10  485  	 * cache flush; it is necessary even after writing invalid entries.
07037db5d479f9 Palmer Dabbelt          2017-07-10  486  	 * Relying on flush_tlb_fix_spurious_fault would suffice, but
07037db5d479f9 Palmer Dabbelt          2017-07-10  487  	 * the extra traps reduce performance.  So, eagerly SFENCE.VMA.
07037db5d479f9 Palmer Dabbelt          2017-07-10  488  	 */
864609c6a0b5f0 Matthew Wilcox (Oracle  2023-08-02  489) 	while (nr--)
864609c6a0b5f0 Matthew Wilcox (Oracle  2023-08-02  490) 		local_flush_tlb_page(address + nr * PAGE_SIZE);
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  491  
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  492  svvptc:
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  493  	/*
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  494  	 * Svvptc guarantees that the new valid pte will be visible within
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  495  	 * a bounded timeframe, so when the uarch does not cache invalid
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  496  	 * entries, we don't have to do anything.
b5bdff9ee1fdca Alexandre Ghiti         2024-07-02  497  	 */
07037db5d479f9 Palmer Dabbelt          2017-07-10 @498  }
864609c6a0b5f0 Matthew Wilcox (Oracle  2023-08-02  499) #define update_mmu_cache(vma, addr, ptep) \
864609c6a0b5f0 Matthew Wilcox (Oracle  2023-08-02  500) 	update_mmu_cache_range(NULL, vma, addr, ptep, 1)
07037db5d479f9 Palmer Dabbelt          2017-07-10  501  

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