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authorMark Rutland <mark.rutland@arm.com>2016-08-11 14:11:05 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2016-08-12 18:46:29 +0100
commit0194e760f7d2f42adb5e1db31b27a4331dd89c2f (patch)
treebed2101068d2cc4aa7a29ee6466d328166ca478d
parent9adeb8e72dbfe976709df01e259ed556ee60e779 (diff)
arm64: hibernate: avoid potential TLB conflict
In create_safe_exec_page we install a set of global mappings in TTBR0, then subsequently invalidate TLBs. While TTBR0 points at the zero page, and the TLBs should be free of stale global entries, we may have stale ASID-tagged entries (e.g. from the EFI runtime services mappings) for the same VAs. Per the ARM ARM these ASID-tagged entries may conflict with newly-allocated global entries, and we must follow a Break-Before-Make approach to avoid issues resulting from this. This patch reworks create_safe_exec_page to invalidate TLBs while the zero page is still in place, ensuring that there are no potential conflicts when the new TTBR0 value is installed. As a single CPU is online while this code executes, we do not need to perform broadcast TLB maintenance, and can call local_flush_tlb_all(), which also subsumes some barriers. The remaining assembly is converted to use write_sysreg() and isb(). Other than this, we safely manipulate TTBRs in the hibernate dance. The code we install as part of the new TTBR0 mapping (the hibernated kernel's swsusp_arch_suspend_exit) installs a zero page into TTBR1, invalidates TLBs, then installs its preferred value. Upon being restored to the middle of swsusp_arch_suspend, the new image will call __cpu_suspend_exit, which will call cpu_uninstall_idmap, installing the zero page in TTBR0 and invalidating all TLB entries. Fixes: 82869ac57b5d ("arm64: kernel: Add support for hibernate/suspend-to-disk") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: James Morse <james.morse@arm.com> Tested-by: James Morse <james.morse@arm.com> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: <stable@vger.kernel.org> # 4.7+ Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/kernel/hibernate.c23
1 files changed, 17 insertions, 6 deletions
diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index 21ab5df9fa76..b2e7de8726e8 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -35,6 +35,7 @@
#include <asm/sections.h>
#include <asm/smp.h>
#include <asm/suspend.h>
+#include <asm/sysreg.h>
#include <asm/virt.h>
/*
@@ -217,12 +218,22 @@ static int create_safe_exec_page(void *src_start, size_t length,
set_pte(pte, __pte(virt_to_phys((void *)dst) |
pgprot_val(PAGE_KERNEL_EXEC)));
- /* Load our new page tables */
- asm volatile("msr ttbr0_el1, %0;"
- "isb;"
- "tlbi vmalle1is;"
- "dsb ish;"
- "isb" : : "r"(virt_to_phys(pgd)));
+ /*
+ * Load our new page tables. A strict BBM approach requires that we
+ * ensure that TLBs are free of any entries that may overlap with the
+ * global mappings we are about to install.
+ *
+ * For a real hibernate/resume cycle TTBR0 currently points to a zero
+ * page, but TLBs may contain stale ASID-tagged entries (e.g. for EFI
+ * runtime services), while for a userspace-driven test_resume cycle it
+ * points to userspace page tables (and we must point it at a zero page
+ * ourselves). Elsewhere we only (un)install the idmap with preemption
+ * disabled, so T0SZ should be as required regardless.
+ */
+ cpu_set_reserved_ttbr0();
+ local_flush_tlb_all();
+ write_sysreg(virt_to_phys(pgd), ttbr0_el1);
+ isb();
*phys_dst_addr = virt_to_phys((void *)dst);