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Subject[PATCH v1 0/4] Fix issues with huge mapping in ioremap
Date
Note: I was working on these patches for quite sometime
and realized that Toshi Kani has shared some patches
addressing the same isssue with subject
"[PATCH 0/2] fix memory leak / panic in ioremap huge pages".
I've taken slightly different approach here, so sending
to the list, finally.

This patch series attempts to fix the issue described in
this discussion: https://lkml.org/lkml/2017/12/23/3

In summary, CONFIG_HAVE_ARCH_HUGE_VMAP has 2 issues
observed on ARM64

1. Stale TLB entries
2. Page table leaks

Will Deacon has by-passed huge mapping for ARM64
until these issues are fixed properly.

I've tested these patches on ARM64 based SDM845
with 4.9 kernel. Hanjun Guo <hanjun.guo@linaro.org>
shared test-case to reproduce this issue in
https://patchwork.kernel.org/patch/10134581/

However, I had no luck reproducing this issue with
exactly this test. I added some more code to reproduce
and here is my test which surfaces this issue in some
five hours of testing.

Test Code:

#define pr_fmt(fmt) "IOREMAP_TEST: " fmt

#include <linux/console.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/random.h>
#include <linux/io.h>
#include <linux/kthread.h>

static int io_remap_test(void *arg)
{
phys_addr_t phy_addr_1 = 0x98000000;
unsigned long block_size = 0x200000;
unsigned long total_size = 0x400000;
unsigned long va_addr_3;
unsigned long va_addr_4;

struct vm_struct *area;

/*
* run this test for 10 hours
*/
u32 times_ms = 10 * 60 * 60 * 1000;
unsigned long timeout = jiffies + msecs_to_jiffies(times_ms);
int rand_type;
int rand_value;
u32 mem_size;
int i;

area = get_vm_area(total_size, VM_IOREMAP);
va_addr_3 = (unsigned long)area->addr;
va_addr_4 = va_addr_3 + block_size;
pr_err("Virtual area %lx -- %lx\n", va_addr_3, va_addr_3 + total_size);

ioremap_page_range(va_addr_3, va_addr_3 + block_size, phy_addr_1, __pgprot(PROT_DEVICE_nGnRE));
pr_err("My tests will run now 2\n");
do {
get_random_bytes(&rand_value, sizeof(u32));

rand_type = rand_value % 6;
switch (rand_type) {
case 0:
mem_size = 0x1000;
break;
case 1:
mem_size = 0x8000;
break;
case 2:
mem_size = 0x200000;
break;
case 3:
mem_size = 0x30000;
break;
case 4:
mem_size = 0x10000;
break;
case 5:
mem_size = 0x40000;
break;
default:
mem_size = 0x4000;
break;
}

/*
* Prompt TLB to speculatively pre-fetch
*/
readq(va_addr_3 + block_size - 0x20);
readq(va_addr_3 + block_size - 0x18);
readq(va_addr_3 + block_size - 0x10);
readq(va_addr_3 + block_size - 0x8);

ioremap_page_range(va_addr_4, va_addr_4 + mem_size, phy_addr_1, __pgprot(PROT_DEVICE_nGnRE));

if (mem_size >= 0x200000 && !(rand_value%10000)) {
schedule();
pr_err("possible error case\n");
}

/*
* Make CPU aware about our access pattern
* Also, these accesses should lead to crash
*/
for (i = 0; i < 5; i++ ) {
readq(va_addr_3 + block_size - 0x20);
readq(va_addr_3 + block_size - 0x18);
readq(va_addr_3 + block_size - 0x10);
readq(va_addr_3 + block_size - 0x8);
// Crash is expected here
readq(va_addr_4);
readq(va_addr_4 + 0x8);
readq(va_addr_4 + 0x10);
readq(va_addr_4 + 0x18);
readq(va_addr_4 + 0x20);
}

unmap_kernel_range(va_addr_4, mem_size);
} while (time_before(jiffies, timeout));

pr_err("my tests ended now\n");
return 0;
}

static int __init ioremap_testing_init(void)
{
struct task_struct *t;
pr_err("my tests will run now 1\n");

t = kthread_create(&io_remap_test, NULL, "ioremap-testing");
/*
* Do this so that we can run this thread on GOLD cores
*/
kthread_bind(t, 6);
wake_up_process(t);
return 0;
}
late_initcall(ioremap_testing_init);


Chintan Pandya (4):
asm/tlbflush: Add flush_tlb_pgtable() for ARM64
ioremap: Invalidate TLB after huge mappings
arm64: Fix the page leak in pud/pmd_set_huge
Revert "arm64: Enforce BBM for huge IO/VMAP mappings"

arch/arm64/include/asm/tlbflush.h | 5 +++++
arch/arm64/mm/mmu.c | 17 ++++++++---------
include/asm-generic/tlb.h | 6 ++++++
lib/ioremap.c | 9 +++++++--
4 files changed, 26 insertions(+), 11 deletions(-)

--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc., is a member of Code Aurora Forum, a Linux Foundation
Collaborative Project

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