io_uring: Fix io_uring_mmu_get_unmapped_area() for IA-64

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 architecture independend get_unmapped_area() search algorithm which doesn't suite the memory 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 <[email protected]>

Fixes d808459b2e31 ("io_uring: Adjust mapping wrt architecture aliasing requirements")

Signed-off-by Helge Deller <[email protected]>

arch/ia64/kernel/sys_ia64.c +0 -0

index 6e948d015332..eb561cc93632 100644
@@ -63,7 +63,7 @@ arch_get_unmapped_area (struct file *filp, unsigned 

long addr, unsigned long len

arch/ia64/kernel/sys_ia64.c +1 -1

 	info.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);
 }

arch/parisc/kernel/sys_parisc.c +0 -1

index 39acccabf2ed..465b7cb9d44f 100644
@@ -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.
*/

arch/parisc/kernel/sys_parisc.c +5 -4

-#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) {

arch/parisc/kernel/sys_parisc.c +0 -0

 		/* Even MAP_FIXED mappings must reside within TASK_SIZE */

io_uring/io_uring.c +0 -2

index f1b79959d1c1..70eb01faf15f 100644
@@ -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;
 

io_uring/io_uring.c +17 -23

 	/*

@@ -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 */

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 architecture independend get_unmapped_area() search algorithm which doesn't suite the memory 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.

Quoted 13 lines · Helge Deller

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 architecture independend get_unmapped_area() search algorithm which doesn't suite the memory 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.

Quoted 6 lines

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.

Any comments from the IA64 folks?

Helge, should this be split into three patches? One for hppa, one for ia64, and then the io_uring one?

Quoted 14 lines · Jens Axboe

Quoted 13 lines · Helge Deller

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 architecture independend get_unmapped_area() search algorithm which doesn't suite the memory 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.

Quoted 8 lines

Quoted 6 lines

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.

Any comments from the IA64 folks?

matoro tested it on ia64 at least...

Quoted 2 lines

Helge, should this be split into three patches? One for hppa, one for ia64, and then the io_uring one?

If we split up, I would prefer to split it into 2 patches:
One for io_uring together with the hppa patch, since they should go in together.

The ia64 patch is probably unrelated, and can go seperately. But there doesn't seem to be any ia64 maintainer...?

Do you have a chance to test this patch on the other io_uring platforms, without applying it into your tree? I think some testing would be good.

Helge

Quoted 40 lines · Helge Deller

Quoted 14 lines · Jens Axboe

Quoted 13 lines · Helge Deller

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 architecture independend get_unmapped_area() search algorithm which doesn't suite the memory 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.

Quoted 8 lines

Quoted 6 lines

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.

Any comments from the IA64 folks?

matoro tested it on ia64 at least...

Quoted 2 lines

Helge, should this be split into three patches? One for hppa, one for ia64, and then the io_uring one?

If we split up, I would prefer to split it into 2 patches: One for io_uring together with the hppa patch, since they should go in together.

The ia64 patch is probably unrelated, and can go seperately. But there doesn't seem to be any ia64 maintainer...?

Do you have a chance to test this patch on the other io_uring platforms, without applying it into your tree? I think some testing would be good.

Quoted 1 line

Helge

I tested this on ppc64le last night just to be sure, still had 100% pass on test suite.

Quoted 14 lines · Jens Axboe

Quoted 13 lines · Helge Deller

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 architecture independend get_unmapped_area() search algorithm which doesn't suite the memory 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.

Quoted 8 lines

Quoted 6 lines

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.

Any comments from the IA64 folks?

matoro tested it on ia64 at least...

Quoted 2 lines

Helge, should this be split into three patches? One for hppa, one for ia64, and then the io_uring one?

If we split up, I would prefer to split it into 2 patches: One for io_uring together with the hppa patch, since they should go in together.

The ia64 patch is probably unrelated, and can go seperately. But there doesn't seem to be any ia64 maintainer...?

Do you have a chance to test this patch on the other io_uring platforms, without applying it into your tree? I think some testing would be good.

Quoted 3 lines

Do you have a chance to test this patch on the other io_uring platforms, without applying it into your tree? I think some testing would be good.

Yep, I can run it on arm64 and x86-64 pretty easily. Will do so.

Quoted 26 lines · Helge Deller

Quoted 14 lines · Jens Axboe

Quoted 13 lines · Helge Deller

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 architecture independend get_unmapped_area() search algorithm which doesn't suite the memory 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.

Quoted 8 lines

Quoted 6 lines

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.

Any comments from the IA64 folks?

matoro tested it on ia64 at least...

Quoted 6 lines

Quoted 2 lines

Helge, should this be split into three patches? One for hppa, one for ia64, and then the io_uring one?

If we split up, I would prefer to split it into 2 patches: One for io_uring together with the hppa patch, since they should go in together.

OK, that makes sense. Want to spin a new version done like that?