[PATCH] arm64: KVM: Invoke compute_layout() before alternatives are applied

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Will Deacon <will@kernel.org>
Subject: [PATCH] arm64: KVM: Invoke compute_layout() before alternatives are applied
Date: Wed, 16 Oct 2019 18:59:53 +0200	[thread overview]
Message-ID: <20191016165953.o6ogh4fdmsjmd2sw@linutronix.de> (raw)

compute_layout() is invoked as part of an alternative fixup under
stop_machine(). This function invokes get_random_long() which acquires a
sleeping lock on -RT which can not be acquired in this context.

Rename compute_layout() to kvm_compute_layout() and invoke it before
stop_machines() invokes the fixups. Add a __init prefix to
kvm_compute_layout() because the caller has it, too (and so the code can
be discarded after boot).

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/arm64/include/asm/alternative.h |  6 ++++++
 arch/arm64/kernel/alternative.c      |  1 +
 arch/arm64/kvm/va_layout.c           | 11 ++++-------
 3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index b9f8d787eea9f..7532f044d713b 100644
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -35,6 +35,12 @@ void apply_alternatives_module(void *start, size_t length);
 static inline void apply_alternatives_module(void *start, size_t length) { }
 #endif
 
+#ifdef CONFIG_KVM_ARM_HOST
+void kvm_compute_layout(void);
+#else
+static inline void kvm_compute_layout(void) { }
+#endif
+
 #define ALTINSTR_ENTRY(feature,cb)					      \
 	" .word 661b - .\n"				/* label           */ \
 	" .if " __stringify(cb) " == 0\n"				      \
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index d1757ef1b1e74..c28652ee06f64 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -238,6 +238,7 @@ static int __apply_alternatives_multi_stop(void *unused)
 void __init apply_alternatives_all(void)
 {
 	/* better not try code patching on a live SMP system */
+	kvm_compute_layout();
 	stop_machine(__apply_alternatives_multi_stop, NULL, cpu_online_mask);
 }
 
diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
index 2cf7d4b606c38..0b9fbdf0aaddd 100644
--- a/arch/arm64/kvm/va_layout.c
+++ b/arch/arm64/kvm/va_layout.c
@@ -22,12 +22,15 @@ static u8 tag_lsb;
 static u64 tag_val;
 static u64 va_mask;
 
-static void compute_layout(void)
+__init void kvm_compute_layout(void)
 {
 	phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
 	u64 hyp_va_msb;
 	int kva_msb;
 
+	if (WARN_ON(va_mask))
+		return;
+
 	/* Where is my RAM region? */
 	hyp_va_msb  = idmap_addr & BIT(vabits_actual - 1);
 	hyp_va_msb ^= BIT(vabits_actual - 1);
@@ -110,9 +113,6 @@ void __init kvm_update_va_mask(struct alt_instr *alt,
 
 	BUG_ON(nr_inst != 5);
 
-	if (!has_vhe() && !va_mask)
-		compute_layout();
-
 	for (i = 0; i < nr_inst; i++) {
 		u32 rd, rn, insn, oinsn;
 
@@ -156,9 +156,6 @@ void kvm_patch_vector_branch(struct alt_instr *alt,
 		return;
 	}
 
-	if (!va_mask)
-		compute_layout();
-
 	/*
 	 * Compute HYP VA by using the same computation as kern_hyp_va()
 	 */
-- 
2.23.0

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