On 2023-07-19 17:20, Helge Deller wrote:
The io_uring testcase is broken on IA-64 since commit d808459b2e31 ("io_uring: Adjust mapping wrt architecture aliasing requirements"). The reason is, that this commit introduced an own architectureindependend get_unmapped_area() search algorithm which doesn't suite thememory region requirements for IA-64. To avoid similar problems in the future it's better to switch back to the architecture-provided get_unmapped_area() function and adjust the needed input parameters before the call. Additionally io_uring_mmu_get_unmapped_area() will now become easier to understand and maintain. This patch has been tested on physical IA-64 and PA-RISC machines, without any failures in the io_uring testcases. On PA-RISC the LTP mmmap testcases did not report any regressions either. I don't expect issues for other architectures, but it would be nice if this patch could be tested on other machines too. Reported-by: matoro <matoro_mailinglist_kernel@xxxxxxxxx>Fixes: d808459b2e31 ("io_uring: Adjust mapping wrt architecture aliasing requirements")Signed-off-by: Helge Deller <deller@xxxxxx> diff --git a/arch/ia64/kernel/sys_ia64.c b/arch/ia64/kernel/sys_ia64.c index 6e948d015332..eb561cc93632 100644 --- a/arch/ia64/kernel/sys_ia64.c +++ b/arch/ia64/kernel/sys_ia64.c@@ -63,7 +63,7 @@ arch_get_unmapped_area (struct file *filp, unsigned long addr, unsigned long leninfo.low_limit = addr; info.high_limit = TASK_SIZE; info.align_mask = align_mask; - info.align_offset = 0; + info.align_offset = pgoff << PAGE_SHIFT; return vm_unmapped_area(&info); }diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.cindex 39acccabf2ed..465b7cb9d44f 100644 --- a/arch/parisc/kernel/sys_parisc.c +++ b/arch/parisc/kernel/sys_parisc.c @@ -26,12 +26,17 @@ #include <linux/compat.h> /*- * Construct an artificial page offset for the mapping based on the physical + * Construct an artificial page offset for the mapping based on the virtual* address of the kernel file mapping variable.+ * If filp is zero the calculated pgoff value aliases the memory of the given + * address. This is useful for io_uring where the mapping shall alias a kernel + * address and a userspace adress where both the kernel and the userspace+ * access the same memory region. */ -#define GET_FILP_PGOFF(filp) \ - (filp ? (((unsigned long) filp->f_mapping) >> 8) \ - & ((SHM_COLOUR-1) >> PAGE_SHIFT) : 0UL) +#define GET_FILP_PGOFF(filp, addr) \ + ((filp ? (((unsigned long) filp->f_mapping) >> 8) \ + & ((SHM_COLOUR-1) >> PAGE_SHIFT) : 0UL) \ + + (addr >> PAGE_SHIFT)) static unsigned long shared_align_offset(unsigned long filp_pgoff, unsigned long pgoff)@@ -111,7 +116,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,do_color_align = 0; if (filp || (flags & MAP_SHARED)) do_color_align = 1; - filp_pgoff = GET_FILP_PGOFF(filp); + filp_pgoff = GET_FILP_PGOFF(filp, addr); if (flags & MAP_FIXED) { /* Even MAP_FIXED mappings must reside within TASK_SIZE */ diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index f1b79959d1c1..70eb01faf15f 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c@@ -3425,8 +3425,6 @@ static unsigned long io_uring_mmu_get_unmapped_area(struct file *filp,unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { - const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags); - struct vm_unmapped_area_info info; void *ptr; /*@@ -3441,32 +3439,26 @@ static unsigned long io_uring_mmu_get_unmapped_area(struct file *filp,if (IS_ERR(ptr)) return -ENOMEM; - info.flags = VM_UNMAPPED_AREA_TOPDOWN; - info.length = len; - info.low_limit = max(PAGE_SIZE, mmap_min_addr); - info.high_limit = arch_get_mmap_base(addr, current->mm->mmap_base); + /* + * Some architectures have strong cache aliasing requirements. + * For such architectures we need a coherent mapping which aliases + * kernel memory *and* userspace memory. To achieve that: + * - use a NULL file pointer to reference physical memory, and + * - use the kernel virtual address of the shared io_uring context + * (instead of the userspace-provided address, which has to be 0UL + * anyway). + * For architectures without such aliasing requirements, the + * architecture will return any suitable mapping because addr is 0. + */ + filp = NULL; + flags |= MAP_SHARED; + pgoff = 0; /* has been translated to ptr above */ #ifdef SHM_COLOUR - info.align_mask = PAGE_MASK & (SHM_COLOUR - 1UL); + addr = (uintptr_t) ptr; #else - info.align_mask = PAGE_MASK & (SHMLBA - 1UL); + addr = 0UL; #endif - info.align_offset = (unsigned long) ptr; - - /* - * A failed mmap() very likely causes application failure, - * so fall back to the bottom-up function here. This scenario - * can happen with large stack limits and large mmap() - * allocations. - */ - addr = vm_unmapped_area(&info); - if (offset_in_page(addr)) { - info.flags = 0; - info.low_limit = TASK_UNMAPPED_BASE; - info.high_limit = mmap_end; - addr = vm_unmapped_area(&info); - } - - return addr; + return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); } #else /* !CONFIG_MMU */
Tested-by: matoro <matoro_mailinglist_kernel@xxxxxxxxx>On 6.4.4. The NFS thing I mentioned in our previous emails appears to be a separate regression not related to io_uring.
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