From: Hanjun Guo <guohanjun@huawei.com>
To: <linux-kernel@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>
Cc: <linuxarm@huawei.com>, <linux-mm@kvack.org>,
Hanjun Guo <hanjun.guo@linaro.org>,
Toshi Kani <toshi.kani@hpe.com>,
Mark Rutland <mark.rutland@arm.com>,
Will Deacon <will.deacon@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Michal Hocko <mhocko@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Xuefeng Wang <wxf.wang@hisilicon.com>
Subject: [RFC patch] ioremap: don't set up huge I/O mappings when p4d/pud/pmd is zero
Date: Thu, 28 Dec 2017 19:24:21 +0800 [thread overview]
Message-ID: <1514460261-65222-1-git-send-email-guohanjun@huawei.com> (raw)
From: Hanjun Guo <hanjun.guo@linaro.org>
When we using iounmap() to free the 4K mapping, it just clear the PTEs
but leave P4D/PUD/PMD unchanged, also will not free the memory of page
tables.
This will cause issues on ARM64 platform (not sure if other archs have
the same issue) for this case:
1. ioremap a 4K size, valid page table will build,
2. iounmap it, pte0 will set to 0;
3. ioremap the same address with 2M size, pgd/pmd is unchanged,
then set the a new value for pmd;
4. pte0 is leaked;
5. CPU may meet exception because the old pmd is still in TLB,
which will lead to kernel panic.
Fix it by skip setting up the huge I/O mappings when p4d/pud/pmd is
zero.
Reported-by: Lei Li <lious.lilei@hisilicon.com>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Xuefeng Wang <wxf.wang@hisilicon.com>
---
Not sure if this is the right direction, this patch has a obvious
side effect that a mapped address with 4K will not back to 2M. I may
miss something and just wrong, so this is just a RFC version, comments
are welcomed.
lib/ioremap.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/lib/ioremap.c b/lib/ioremap.c
index b808a39..4e6f19a 100644
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -89,7 +89,7 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
do {
next = pmd_addr_end(addr, end);
- if (ioremap_pmd_enabled() &&
+ if (ioremap_pmd_enabled() && pmd_none(*pmd) &&
((next - addr) == PMD_SIZE) &&
IS_ALIGNED(phys_addr + addr, PMD_SIZE)) {
if (pmd_set_huge(pmd, phys_addr + addr, prot))
@@ -115,7 +115,7 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr,
do {
next = pud_addr_end(addr, end);
- if (ioremap_pud_enabled() &&
+ if (ioremap_pud_enabled() && pud_none(*pud) &&
((next - addr) == PUD_SIZE) &&
IS_ALIGNED(phys_addr + addr, PUD_SIZE)) {
if (pud_set_huge(pud, phys_addr + addr, prot))
@@ -141,7 +141,7 @@ static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr,
do {
next = p4d_addr_end(addr, end);
- if (ioremap_p4d_enabled() &&
+ if (ioremap_p4d_enabled() && p4d_none(*p4d) &&
((next - addr) == P4D_SIZE) &&
IS_ALIGNED(phys_addr + addr, P4D_SIZE)) {
if (p4d_set_huge(p4d, phys_addr + addr, prot))
--
1.7.12.4
next reply other threads:[~2017-12-28 11:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-28 11:24 Hanjun Guo [this message]
2017-12-29 8:00 ` [RFC patch] ioremap: don't set up huge I/O mappings when p4d/pud/pmd is zero Hanjun Guo
2018-01-05 22:15 ` Kani, Toshi
2018-01-06 9:46 ` Hanjun Guo
2018-01-08 23:36 ` Kani, Toshi
2018-02-20 9:24 ` Chintan Pandya
2018-02-21 0:34 ` Kani, Toshi
[not found] ` <etPan.5a8d2180.1dbfd272.49b8@localhost>
2018-02-21 11:57 ` 答复: " Will Deacon
[not found] ` <32c9b1c3-086b-ba54-f9e9-aefa50066730@huawei.com>
2018-02-26 11:04 ` Will Deacon
[not found] ` <a80e540f-f3bd-53da-185d-7fffe801f10c@huawei.com>
2018-02-27 19:49 ` Kani, Toshi
2018-02-27 19:59 ` Will Deacon
2018-02-27 20:02 ` Kani, Toshi
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