arm64: KVM: Dynamically patch the kernel/hyp VA mask (2b4d1606) · Commits · 戴 / test

arch/arm64/include/asm/kvm_mmu.h

+13 −33

Original line number	Diff line number	Diff line
		@@ -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 +78,15 @@
		* 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 <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;
		}

arch/arm64/kvm/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -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

arch/arm64/kvm/va_layout.c

0 → 100644

+91 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2017 ARM Ltd.
		* Author: Marc Zyngier <marc.zyngier@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_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);
		}
		}

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