From 5b7a08e0ea5bb51f886f2f5e2373de2bf5981dd2 Mon Sep 17 00:00:00 2001

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Date: Thu, 28 Nov 2019 20:58:05 +0100

Subject: [PATCH 1/2] arm64: KVM: Invoke compute_layout() before alternatives

 are applied

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_machine() applies the alternatives. Add a __init prefix to

kvm_compute_layout() because the caller has it, too (and so the code can be

discarded after boot).

Reviewed-by: James Morse <james.morse@arm.com>

Acked-by: Marc Zyngier <maz@kernel.org>

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

---

 arch/arm64/include/asm/kvm_mmu.h | 1 +

 arch/arm64/kernel/smp.c          | 4 ++++

 arch/arm64/kvm/va_layout.c       | 8 +-------

 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h

index befe37d..53d846f 100644

--- a/arch/arm64/include/asm/kvm_mmu.h

+++ b/arch/arm64/include/asm/kvm_mmu.h

@@ -91,6 +91,7 @@

 void kvm_update_va_mask(struct alt_instr *alt,

 			__le32 *origptr, __le32 *updptr, int nr_inst);

+void kvm_compute_layout(void);

 static inline unsigned long __kern_hyp_va(unsigned long v)

 {

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c

index dc9fe87..02d41ea 100644

--- a/arch/arm64/kernel/smp.c

+++ b/arch/arm64/kernel/smp.c

@@ -31,6 +31,7 @@

 #include <linux/of.h>

 #include <linux/irq_work.h>

 #include <linux/kexec.h>

+#include <linux/kvm_host.h>

 #include <asm/alternative.h>

 #include <asm/atomic.h>

@@ -39,6 +40,7 @@

 #include <asm/cputype.h>

 #include <asm/cpu_ops.h>

 #include <asm/daifflags.h>

+#include <asm/kvm_mmu.h>

 #include <asm/mmu_context.h>

 #include <asm/numa.h>

 #include <asm/pgtable.h>

@@ -408,6 +410,8 @@ static void __init hyp_mode_check(void)

 			   "CPU: CPUs started in inconsistent modes");

 	else

 		pr_info("CPU: All CPU(s) started at EL1\n");

+	if (IS_ENABLED(CONFIG_KVM_ARM_HOST))

+		kvm_compute_layout();

 }

 void __init smp_cpus_done(unsigned int max_cpus)

diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c

index 2cf7d4b..dab1fea 100644

--- a/arch/arm64/kvm/va_layout.c

+++ b/arch/arm64/kvm/va_layout.c

@@ -22,7 +22,7 @@

 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;

@@ -110,9 +110,6 @@ 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 +153,6 @@ 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()

 	 */

-- 

1.8.3.1

From d2d093ca412b7fd66acd745d00e3ebd4764fe127 Mon Sep 17 00:00:00 2001

From: Russell King <rmk+kernel@armlinux.org.uk>

Date: Sat, 28 Dec 2019 11:57:14 +0000

Subject: [PATCH 2/2] arm64: kvm: Fix IDMAP overlap with HYP VA

Booting 5.4 on LX2160A reveals that KVM is non-functional:

kvm: Limiting the IPA size due to kernel Virtual Address limit

kvm [1]: IPA Size Limit: 43bits

kvm [1]: IDMAP intersecting with HYP VA, unable to continue

kvm [1]: error initializing Hyp mode: -22

Debugging shows:

kvm [1]: IDMAP page: 81a26000

kvm [1]: HYP VA range: 0:22ffffffff

as RAM is located at:

80000000-fbdfffff : System RAM

2080000000-237fffffff : System RAM

Comparing this with the same kernel on Armada 8040 shows:

kvm: Limiting the IPA size due to kernel Virtual Address limit

kvm [1]: IPA Size Limit: 43bits

kvm [1]: IDMAP page: 2a26000

kvm [1]: HYP VA range: 4800000000:493fffffff

...

kvm [1]: Hyp mode initialized successfully

which indicates that hyp_va_msb is set, and is always set to the

opposite value of the idmap page to avoid the overlap. This does not

happen with the LX2160A.

Further debugging shows vabits_actual = 39, kva_msb = 38 on LX2160A and

kva_msb = 33 on Armada 8040. Looking at the bit layout of the HYP VA,

there is still one bit available for hyp_va_msb. Set this bit

appropriately. This allows KVM to be functional on the LX2160A, but

without any HYP VA randomisation:

kvm: Limiting the IPA size due to kernel Virtual Address limit

kvm [1]: IPA Size Limit: 43bits

kvm [1]: IDMAP page: 81a24000

kvm [1]: HYP VA range: 4000000000:62ffffffff

...

kvm [1]: Hyp mode initialized successfully

Fixes: ed57cac83e05 ("arm64: KVM: Introduce EL2 VA randomisation")

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

[maz: small additional cleanups, preserved case where the tag

 is legitimately 0 and we can just use the mask, Fixes tag]

Signed-off-by: Marc Zyngier <maz@kernel.org>

Link: https://lore.kernel.org/r/E1ilAiY-0000MA-RG@rmk-PC.armlinux.org.uk

---

 arch/arm64/kvm/va_layout.c | 56 +++++++++++++++++++++-------------------------

 1 file changed, 25 insertions(+), 31 deletions(-)

diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c

index dab1fea..a4f48c1 100644

--- a/arch/arm64/kvm/va_layout.c

+++ b/arch/arm64/kvm/va_layout.c

@@ -13,52 +13,46 @@

 #include <asm/kvm_mmu.h>

 /*

- * The LSB of the random hyp VA tag or 0 if no randomization is used.

+ * The LSB of the HYP VA tag

  */

 static u8 tag_lsb;

 /*

- * The random hyp VA tag value with the region bit if hyp randomization is used

+ * The HYP VA tag value with the region bit

  */

 static u64 tag_val;

 static u64 va_mask;

+/*

+ * We want to generate a hyp VA with the following format (with V ==

+ * vabits_actual):

+ *

+ *  63 ... V |     V-1    | V-2 .. tag_lsb | tag_lsb - 1 .. 0

+ *  ---------------------------------------------------------

+ * | 0000000 | hyp_va_msb |   random tag   |  kern linear VA |

+ *           |--------- tag_val -----------|----- va_mask ---|

+ *

+ * which does not conflict with the idmap regions.

+ */

 __init void kvm_compute_layout(void)

 {

 	phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);

 	u64 hyp_va_msb;

-	int kva_msb;

 	/* Where is my RAM region? */

 	hyp_va_msb  = idmap_addr & BIT(vabits_actual - 1);

 	hyp_va_msb ^= BIT(vabits_actual - 1);

-	kva_msb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^

+	tag_lsb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^

 			(u64)(high_memory - 1));

-	if (kva_msb == (vabits_actual - 1)) {

-		/*

-		 * No space in the address, let's compute the mask so

-		 * that it covers (vabits_actual - 1) bits, and the region

-		 * bit. The tag stays set to zero.

-		 */

-		va_mask  = BIT(vabits_actual - 1) - 1;

-		va_mask |= hyp_va_msb;

-	} else {

-		/*

-		 * We do have some free bits to insert a random tag.

-		 * Hyp VAs are now created from kernel linear map VAs

-		 * using the following formula (with V == vabits_actual):

-		 *

-		 *  63 ... V |     V-1    | V-2 .. tag_lsb | tag_lsb - 1 .. 0

-		 *  ---------------------------------------------------------

-		 * | 0000000 | hyp_va_msb |    random tag  |  kern linear VA |

-		 */

-		tag_lsb = kva_msb;

-		va_mask = GENMASK_ULL(tag_lsb - 1, 0);

-		tag_val = get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb);

-		tag_val |= hyp_va_msb;

-		tag_val >>= tag_lsb;

+	va_mask = GENMASK_ULL(tag_lsb - 1, 0);

+	tag_val = hyp_va_msb;

+

+	if (tag_lsb != (vabits_actual - 1)) {

+		/* We have some free bits to insert a random tag. */

+		tag_val |= get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb);

 	}

+	tag_val >>= tag_lsb;

 }

 static u32 compute_instruction(int n, u32 rd, u32 rn)

@@ -117,11 +111,11 @@ void __init kvm_update_va_mask(struct alt_instr *alt,

 		 * VHE doesn't need any address translation, let's NOP

 		 * everything.

 		 *

-		 * Alternatively, if we don't have any spare bits in

-		 * the address, NOP everything after masking that

-		 * kernel VA.

+		 * Alternatively, if the tag is zero (because the layout

+		 * dictates it and we don't have any spare bits in the

+		 * address), NOP everything after masking the kernel VA.

 		 */

-		if (has_vhe() || (!tag_lsb && i > 0)) {

+		if (has_vhe() || (!tag_val && i > 0)) {

 			updptr[i] = cpu_to_le32(aarch64_insn_gen_nop());

 			continue;

 		}

-- 

1.8.3.1