From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
npiggin@gmail.com, Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Subject: [PATCH v4 06/22] powerpc/mce: Don't reload pte val in addr_to_pfn
Date: Tue, 5 May 2020 12:47:13 +0530 [thread overview]
Message-ID: <20200505071729.54912-7-aneesh.kumar@linux.ibm.com> (raw)
In-Reply-To: <20200505071729.54912-1-aneesh.kumar@linux.ibm.com>
A lockless page table walk should be safe against parallel THP collapse, THP
split and madvise(MADV_DONTNEED)/parallel fault. This patch makes sure kernel
won't reload the pteval when checking for different conditions. The patch also added
a check for pte_present to make sure the kernel is indeed operating
on a PTE and not a pointer to level 0 table page.
The pfn value we find here can be different from the actual pfn on which
machine check happened. This can happen if we raced with a parallel update
of the page table. In such a scenario we end up isolating a wrong pfn. But that
doesn't have any other side effect.
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
arch/powerpc/kernel/mce_power.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index 067b094bfeff..1d18991f3854 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -27,7 +27,7 @@
*/
unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
{
- pte_t *ptep;
+ pte_t *ptep, pte;
unsigned int shift;
unsigned long pfn, flags;
struct mm_struct *mm;
@@ -39,19 +39,23 @@ unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
local_irq_save(flags);
ptep = __find_linux_pte(mm->pgd, addr, NULL, &shift);
+ if (!ptep) {
+ pfn = ULONG_MAX;
+ goto out;
+ }
+ pte = READ_ONCE(*ptep);
- if (!ptep || pte_special(*ptep)) {
+ if (!pte_present(pte) || pte_special(pte)) {
pfn = ULONG_MAX;
goto out;
}
if (shift <= PAGE_SHIFT)
- pfn = pte_pfn(*ptep);
+ pfn = pte_pfn(pte);
else {
unsigned long rpnmask = (1ul << shift) - PAGE_SIZE;
- pfn = pte_pfn(__pte(pte_val(*ptep) | (addr & rpnmask)));
+ pfn = pte_pfn(__pte(pte_val(pte) | (addr & rpnmask)));
}
-
out:
local_irq_restore(flags);
return pfn;
--
2.26.2
next prev parent reply other threads:[~2020-05-05 7:39 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 7:17 [PATCH v4 00/22] Avoid IPI while updating page table entries Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 01/22] powerpc/pkeys: Avoid using lockless page table walk Aneesh Kumar K.V
2020-05-13 8:49 ` Michael Ellerman
2020-05-05 7:17 ` [PATCH v4 02/22] powerpc/pkeys: Check vma before returning key fault error to the user Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 03/22] powerpc/mm/hash64: use _PAGE_PTE when checking for pte_present Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 04/22] powerpc/hash64: Restrict page table lookup using init_mm with __flush_hash_table_range Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 05/22] powerpc/book3s64/hash: Use the pte_t address from the caller Aneesh Kumar K.V
2020-05-05 7:17 ` Aneesh Kumar K.V [this message]
2020-05-05 7:17 ` [PATCH v4 07/22] powerpc/perf/callchain: Use __get_user_pages_fast in read_user_stack_slow Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 08/22] powerpc/kvm/book3s: switch from raw_spin_*lock to arch_spin_lock Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 09/22] powerpc/kvm/book3s: Add helper to walk partition scoped linux page table Aneesh Kumar K.V
2020-05-28 1:43 ` Paul Mackerras
2020-05-28 6:01 ` Aneesh Kumar K.V
2020-05-28 7:25 ` Paul Mackerras
2020-05-05 7:17 ` [PATCH v4 10/22] powerpc/kvm/nested: Add helper to walk nested shadow " Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 11/22] powerpc/kvm/book3s: Use kvm helpers to walk shadow or secondary table Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 12/22] powerpc/kvm/book3s: Add helper for host page table walk Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 13/22] powerpc/kvm/book3s: Use find_kvm_host_pte in page fault handler Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 14/22] powerpc/kvm/book3s: Use find_kvm_host_pte in h_enter Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 15/22] powerpc/kvm/book3s: use find_kvm_host_pte in pute_tce functions Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 16/22] powerpc/kvm/book3s: Avoid using rmap to protect parallel page table update Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 17/22] powerpc/kvm/book3s: use find_kvm_host_pte in kvmppc_book3s_instantiate_page Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 18/22] powerpc/kvm/book3s: Use find_kvm_host_pte in kvmppc_get_hpa Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 19/22] powerpc/kvm/book3s: Use pte_present instead of opencoding _PAGE_PRESENT check Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 20/22] powerpc/mm/book3s64: Avoid sending IPI on clearing PMD Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 21/22] mm: change pmdp_huge_get_and_clear_full take vm_area_struct as arg Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 22/22] powerpc/mm/book3s64: Fix MADV_DONTNEED and parallel page fault race Aneesh Kumar K.V
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200505071729.54912-7-aneesh.kumar@linux.ibm.com \
--to=aneesh.kumar@linux.ibm.com \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mahesh@linux.vnet.ibm.com \
--cc=mpe@ellerman.id.au \
--cc=npiggin@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).