linux-kernel - [PATCH v13 06/18] arm64: hibernate: abstract ttrb0 setup function

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Date:   Thu,  8 Apr 2021 00:05:25 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     pasha.tatashin@...een.com, jmorris@...ei.org, sashal@...nel.org,
        ebiederm@...ssion.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, corbet@....net,
        catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, maz@...nel.org,
        james.morse@....com, vladimir.murzin@....com,
        matthias.bgg@...il.com, linux-mm@...ck.org, mark.rutland@....com,
        steve.capper@....com, rfontana@...hat.com, tglx@...utronix.de,
        selindag@...il.com, tyhicks@...ux.microsoft.com,
        kernelfans@...il.com
Subject: [PATCH v13 06/18] arm64: hibernate: abstract ttrb0 setup function

Currently, only hibernate sets custom ttbr0 with safe idmaped function.
Kexec, is also going to be using this functinality when relocation code
is going to be idmapped.

Move the setup seqeuence to a dedicated cpu_install_ttbr0() for custom
ttbr0.

Suggested-by: James Morse <james.morse@....com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
---
 arch/arm64/include/asm/mmu_context.h | 24 ++++++++++++++++++++++++
 arch/arm64/kernel/hibernate.c        | 21 +--------------------
 2 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index bd02e99b1a4c..f64d0d5e1b1f 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -115,6 +115,30 @@ static inline void cpu_install_idmap(void)
 	cpu_switch_mm(lm_alias(idmap_pg_dir), &init_mm);
 }
 
+/*
+ * 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/kexec 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).
+ *
+ * We change T0SZ as part of installing the idmap. This is undone by
+ * cpu_uninstall_idmap() in __cpu_suspend_exit().
+ */
+static inline void cpu_install_ttbr0(phys_addr_t ttbr0, unsigned long t0sz)
+{
+	cpu_set_reserved_ttbr0();
+	local_flush_tlb_all();
+	__cpu_set_tcr_t0sz(t0sz);
+
+	/* avoid cpu_switch_mm() and its SW-PAN and CNP interactions */
+	write_sysreg(ttbr0, ttbr0_el1);
+	isb();
+}
+
 /*
  * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD,
  * avoiding the possibility of conflicting TLB entries being allocated.
diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index 0b8bad8bb6eb..ded5115bcb63 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -206,26 +206,7 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	if (rc)
 		return rc;
 
-	/*
-	 * 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).
-	 *
-	 * We change T0SZ as part of installing the idmap. This is undone by
-	 * cpu_uninstall_idmap() in __cpu_suspend_exit().
-	 */
-	cpu_set_reserved_ttbr0();
-	local_flush_tlb_all();
-	__cpu_set_tcr_t0sz(t0sz);
-	write_sysreg(trans_ttbr0, ttbr0_el1);
-	isb();
-
+	cpu_install_ttbr0(trans_ttbr0, t0sz);
 	*phys_dst_addr = virt_to_phys(page);
 
 	return 0;
-- 
2.25.1