From: Pavel Tatashin <pasha.tatashin@oracle.com>
To: steven.sistare@oracle.com, linux-kernel@vger.kernel.org,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
x86@kernel.org, gregkh@linuxfoundation.org, jkosina@suse.cz,
hughd@google.com, dave.hansen@linux.intel.com, luto@kernel.org,
torvalds@linux-foundation.org
Subject: [PATCH 4.9] x86/pti/efi: broken conversion from efi to kernel page table
Date: Thu, 11 Jan 2018 16:58:20 -0500 [thread overview]
Message-ID: <20180111215820.29736-1-pasha.tatashin@oracle.com> (raw)
The page table order must be increased for EFI table in order to avoid a
bug where NMI tries to change the page table to kernel page table, while
efi page table is active.
For more disccussion about this bug, see this thread:
http://lkml.iu.edu/hypermail/linux/kernel/1801.1/00951.html
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
---
arch/x86/include/asm/pgalloc.h | 11 +++++++++++
arch/x86/platform/efi/efi_64.c | 2 +-
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h
index b6d425999f99..1178a51b77f3 100644
--- a/arch/x86/include/asm/pgalloc.h
+++ b/arch/x86/include/asm/pgalloc.h
@@ -27,6 +27,17 @@ static inline void paravirt_release_pud(unsigned long pfn) {}
*/
extern gfp_t __userpte_alloc_gfp;
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+/*
+ * Instead of one PGD, we acquire two PGDs. Being order-1, it is
+ * both 8k in size and 8k-aligned. That lets us just flip bit 12
+ * in a pointer to swap between the two 4k halves.
+ */
+#define PGD_ALLOCATION_ORDER 1
+#else
+#define PGD_ALLOCATION_ORDER 0
+#endif
+
/*
* Allocate and free page tables.
*/
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 2f25a363068c..dcb2d9d185a2 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -142,7 +142,7 @@ int __init efi_alloc_page_tables(void)
return 0;
gfp_mask = GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO;
- efi_pgd = (pgd_t *)__get_free_page(gfp_mask);
+ efi_pgd = (pgd_t *)__get_free_pages(gfp_mask, PGD_ALLOCATION_ORDER);
if (!efi_pgd)
return -ENOMEM;
--
1.8.3.1
next reply other threads:[~2018-01-11 21:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-11 21:58 Pavel Tatashin [this message]
2018-01-12 13:58 ` [PATCH 4.9] x86/pti/efi: broken conversion from efi to kernel page table Ingo Molnar
2018-01-12 14:09 ` Pavel Tatashin
2018-01-12 14:27 ` Jiri Kosina
2018-01-13 13:16 ` Greg KH
2018-01-13 13:18 ` Greg KH
2018-01-13 17:12 ` Greg KH
2018-01-13 17:40 ` Pavel Tatashin
2018-01-13 18:14 ` Greg KH
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