From 2b4d1606aac27f2485061abd953ea1e103b5e26e Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sun, 3 Dec 2017 17:36:55 +0000 Subject: [PATCH] arm64: KVM: Dynamically patch the kernel/hyp VA mask 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 cumulative masking we have at the moment) or even a single NOP on VHE. This also adds some initial code that will allow the patching callback to switch to a more complex patching. Acked-by: Catalin Marinas Reviewed-by: James Morse Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_mmu.h | 46 +++++----------- arch/arm64/kvm/Makefile | 2 +- arch/arm64/kvm/va_layout.c | 91 ++++++++++++++++++++++++++++++++ 3 files changed, 105 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 cffa34e23718..0656c79d968f 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 @@ -81,28 +78,15 @@ * 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 (kvm_update_va_mask uses the + * specific registers encoded in the instructions). */ .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 +97,14 @@ alternative_else_nop_endif #include #include +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..0d7bf8319894 --- /dev/null +++ b/arch/arm64/kvm/va_layout.c @@ -0,0 +1,91 @@ +/* + * Copyright (C) 2017 ARM Ltd. + * Author: Marc Zyngier + * + * 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 . + */ + +#include +#include +#include +#include +#include + +#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_LOW_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 single instruction in the alternative 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] = cpu_to_le32(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); + } +} -- GitLab