[PATCH v4 08/19] arm64: KVM: Dynamically patch the kernel/hyp VA mask
Marc Zyngier
marc.zyngier at arm.com
Thu Jan 4 10:43:23 PST 2018
So far, we're using a complicated sequence of alternatives to
patch the kernel/hyp VA mask on non-VHE, and NOP out the
masking altogether when on VHE.
THe newly introduced dynamic patching gives us the opportunity
to simplify that code by patching a single instruction with
the correct mask (instead of the mind bending cummulative masking
we have at the moment) or even a single NOP on VHE.
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
arch/arm64/include/asm/kvm_mmu.h | 45 ++++++--------------
arch/arm64/kvm/Makefile | 2 +-
arch/arm64/kvm/va_layout.c | 91 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 104 insertions(+), 34 deletions(-)
create mode 100644 arch/arm64/kvm/va_layout.c
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 672c8684d5c2..b0c3cbe9b513 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -69,9 +69,6 @@
* mappings, and none of this applies in that case.
*/
-#define HYP_PAGE_OFFSET_HIGH_MASK ((UL(1) << VA_BITS) - 1)
-#define HYP_PAGE_OFFSET_LOW_MASK ((UL(1) << (VA_BITS - 1)) - 1)
-
#ifdef __ASSEMBLY__
#include <asm/alternative.h>
@@ -81,28 +78,14 @@
* Convert a kernel VA into a HYP VA.
* reg: VA to be converted.
*
- * This generates the following sequences:
- * - High mask:
- * and x0, x0, #HYP_PAGE_OFFSET_HIGH_MASK
- * nop
- * - Low mask:
- * and x0, x0, #HYP_PAGE_OFFSET_HIGH_MASK
- * and x0, x0, #HYP_PAGE_OFFSET_LOW_MASK
- * - VHE:
- * nop
- * nop
- *
- * The "low mask" version works because the mask is a strict subset of
- * the "high mask", hence performing the first mask for nothing.
- * Should be completely invisible on any viable CPU.
+ * The actual code generation takes place in kvm_update_va_mask, and
+ * the instructions below are only there to reserve the space and
+ * perform the register allocation.
*/
.macro kern_hyp_va reg
-alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
- and \reg, \reg, #HYP_PAGE_OFFSET_HIGH_MASK
-alternative_else_nop_endif
-alternative_if ARM64_HYP_OFFSET_LOW
- and \reg, \reg, #HYP_PAGE_OFFSET_LOW_MASK
-alternative_else_nop_endif
+alternative_cb kvm_update_va_mask
+ and \reg, \reg, #1
+alternative_cb_end
.endm
#else
@@ -113,18 +96,14 @@ alternative_else_nop_endif
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
+void kvm_update_va_mask(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr, int nr_inst);
+
static inline unsigned long __kern_hyp_va(unsigned long v)
{
- asm volatile(ALTERNATIVE("and %0, %0, %1",
- "nop",
- ARM64_HAS_VIRT_HOST_EXTN)
- : "+r" (v)
- : "i" (HYP_PAGE_OFFSET_HIGH_MASK));
- asm volatile(ALTERNATIVE("nop",
- "and %0, %0, %1",
- ARM64_HYP_OFFSET_LOW)
- : "+r" (v)
- : "i" (HYP_PAGE_OFFSET_LOW_MASK));
+ asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n",
+ kvm_update_va_mask)
+ : "+r" (v));
return v;
}
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 87c4f7ae24de..93afff91cb7c 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -16,7 +16,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/e
kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
-kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o
+kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
kvm-$(CONFIG_KVM_ARM_HOST) += guest.o debug.o reset.o sys_regs.o sys_regs_generic_v8.o
kvm-$(CONFIG_KVM_ARM_HOST) += vgic-sys-reg-v3.o
diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
new file mode 100644
index 000000000000..aee758574e61
--- /dev/null
+++ b/arch/arm64/kvm/va_layout.c
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2017 ARM Ltd.
+ * Author: Marc Zyngier <marc.zyngier at arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kvm_host.h>
+#include <asm/alternative.h>
+#include <asm/debug-monitors.h>
+#include <asm/insn.h>
+#include <asm/kvm_mmu.h>
+
+#define HYP_PAGE_OFFSET_HIGH_MASK ((UL(1) << VA_BITS) - 1)
+#define HYP_PAGE_OFFSET_LOW_MASK ((UL(1) << (VA_BITS - 1)) - 1)
+
+static u64 va_mask;
+
+static void compute_layout(void)
+{
+ phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
+ unsigned long mask = HYP_PAGE_OFFSET_HIGH_MASK;
+
+ /*
+ * Activate the lower HYP offset only if the idmap doesn't
+ * clash with it,
+ */
+ if (idmap_addr > HYP_PAGE_OFFSET_LOW_MASK)
+ mask = HYP_PAGE_OFFSET_HIGH_MASK;
+
+ va_mask = mask;
+}
+
+static u32 compute_instruction(int n, u32 rd, u32 rn)
+{
+ u32 insn = AARCH64_BREAK_FAULT;
+
+ switch (n) {
+ case 0:
+ insn = aarch64_insn_gen_logical_immediate(AARCH64_INSN_LOGIC_AND,
+ AARCH64_INSN_VARIANT_64BIT,
+ rn, rd, va_mask);
+ break;
+ }
+
+ return insn;
+}
+
+void __init kvm_update_va_mask(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr, int nr_inst)
+{
+ int i;
+
+ /* We only expect a 1 instruction sequence */
+ BUG_ON(nr_inst != 1);
+
+ if (!has_vhe() && !va_mask)
+ compute_layout();
+
+ for (i = 0; i < nr_inst; i++) {
+ u32 rd, rn, insn, oinsn;
+
+ /*
+ * VHE doesn't need any address translation, let's NOP
+ * everything.
+ */
+ if (has_vhe()) {
+ updptr[i] = aarch64_insn_gen_nop();
+ continue;
+ }
+
+ oinsn = le32_to_cpu(origptr[i]);
+ rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, oinsn);
+ rn = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RN, oinsn);
+
+ insn = compute_instruction(i, rd, rn);
+ BUG_ON(insn == AARCH64_BREAK_FAULT);
+
+ updptr[i] = cpu_to_le32(insn);
+ }
+}
--
2.14.2
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