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If EL1 generates an asynchronous abort and then traps into EL2 before the abort has been delivered, we may end-up with the abort firing at the worse possible place: on the host. In order to avoid this, it is necessary to take the abort at EL2, by clearing the PSTATE.A bit. In order to survive this abort, we do it at a point where we're in a known state with respect to the world switch, and handle the resulting exception, overloading the exit code in the process. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
199 lines
5.2 KiB
ArmAsm
199 lines
5.2 KiB
ArmAsm
/*
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* Copyright (C) 2015 - ARM Ltd
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* Author: Marc Zyngier <marc.zyngier@arm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/linkage.h>
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#include <asm/asm-offsets.h>
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#include <asm/assembler.h>
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#include <asm/fpsimdmacros.h>
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#include <asm/kvm.h>
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#include <asm/kvm_arm.h>
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#include <asm/kvm_asm.h>
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#include <asm/kvm_mmu.h>
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#define CPU_GP_REG_OFFSET(x) (CPU_GP_REGS + x)
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#define CPU_XREG_OFFSET(x) CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)
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.text
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.pushsection .hyp.text, "ax"
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.macro save_callee_saved_regs ctxt
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stp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
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stp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
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stp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
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stp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
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stp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
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stp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)]
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.endm
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.macro restore_callee_saved_regs ctxt
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ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
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ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
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ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
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ldp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
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ldp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
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ldp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)]
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.endm
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/*
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* u64 __guest_enter(struct kvm_vcpu *vcpu,
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* struct kvm_cpu_context *host_ctxt);
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*/
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ENTRY(__guest_enter)
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// x0: vcpu
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// x1: host context
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// x2-x17: clobbered by macros
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// x18: guest context
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// Store the host regs
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save_callee_saved_regs x1
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// Store the host_ctxt for use at exit time
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str x1, [sp, #-16]!
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add x18, x0, #VCPU_CONTEXT
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// Restore guest regs x0-x17
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ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)]
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ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)]
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ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)]
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ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)]
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ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)]
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ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)]
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ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)]
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ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)]
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ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)]
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// Restore guest regs x19-x29, lr
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restore_callee_saved_regs x18
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// Restore guest reg x18
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ldr x18, [x18, #CPU_XREG_OFFSET(18)]
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// Do not touch any register after this!
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eret
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ENDPROC(__guest_enter)
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ENTRY(__guest_exit)
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// x0: return code
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// x1: vcpu
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// x2-x29,lr: vcpu regs
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// vcpu x0-x1 on the stack
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add x1, x1, #VCPU_CONTEXT
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ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
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// Store the guest regs x2 and x3
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stp x2, x3, [x1, #CPU_XREG_OFFSET(2)]
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// Retrieve the guest regs x0-x1 from the stack
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ldp x2, x3, [sp], #16 // x0, x1
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// Store the guest regs x0-x1 and x4-x18
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stp x2, x3, [x1, #CPU_XREG_OFFSET(0)]
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stp x4, x5, [x1, #CPU_XREG_OFFSET(4)]
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stp x6, x7, [x1, #CPU_XREG_OFFSET(6)]
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stp x8, x9, [x1, #CPU_XREG_OFFSET(8)]
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stp x10, x11, [x1, #CPU_XREG_OFFSET(10)]
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stp x12, x13, [x1, #CPU_XREG_OFFSET(12)]
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stp x14, x15, [x1, #CPU_XREG_OFFSET(14)]
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stp x16, x17, [x1, #CPU_XREG_OFFSET(16)]
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str x18, [x1, #CPU_XREG_OFFSET(18)]
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// Store the guest regs x19-x29, lr
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save_callee_saved_regs x1
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// Restore the host_ctxt from the stack
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ldr x2, [sp], #16
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// Now restore the host regs
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restore_callee_saved_regs x2
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// If we have a pending asynchronous abort, now is the
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// time to find out. From your VAXorcist book, page 666:
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// "Threaten me not, oh Evil one! For I speak with
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// the power of DEC, and I command thee to show thyself!"
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mrs x2, elr_el2
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mrs x3, esr_el2
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mrs x4, spsr_el2
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mov x5, x0
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dsb sy // Synchronize against in-flight ld/st
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msr daifclr, #4 // Unmask aborts
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// This is our single instruction exception window. A pending
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// SError is guaranteed to occur at the earliest when we unmask
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// it, and at the latest just after the ISB.
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.global abort_guest_exit_start
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abort_guest_exit_start:
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isb
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.global abort_guest_exit_end
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abort_guest_exit_end:
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// If the exception took place, restore the EL1 exception
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// context so that we can report some information.
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// Merge the exception code with the SError pending bit.
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tbz x0, #ARM_EXIT_WITH_SERROR_BIT, 1f
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msr elr_el2, x2
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msr esr_el2, x3
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msr spsr_el2, x4
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orr x0, x0, x5
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1: ret
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ENDPROC(__guest_exit)
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ENTRY(__fpsimd_guest_restore)
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stp x2, x3, [sp, #-16]!
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stp x4, lr, [sp, #-16]!
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alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
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mrs x2, cptr_el2
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bic x2, x2, #CPTR_EL2_TFP
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msr cptr_el2, x2
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alternative_else
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mrs x2, cpacr_el1
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orr x2, x2, #CPACR_EL1_FPEN
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msr cpacr_el1, x2
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alternative_endif
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isb
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mrs x3, tpidr_el2
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ldr x0, [x3, #VCPU_HOST_CONTEXT]
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kern_hyp_va x0
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add x0, x0, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
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bl __fpsimd_save_state
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add x2, x3, #VCPU_CONTEXT
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add x0, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
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bl __fpsimd_restore_state
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// Skip restoring fpexc32 for AArch64 guests
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mrs x1, hcr_el2
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tbnz x1, #HCR_RW_SHIFT, 1f
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ldr x4, [x3, #VCPU_FPEXC32_EL2]
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msr fpexc32_el2, x4
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1:
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ldp x4, lr, [sp], #16
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ldp x2, x3, [sp], #16
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ldp x0, x1, [sp], #16
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eret
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ENDPROC(__fpsimd_guest_restore)
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