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Diffstat (limited to 'arch/arm/kvm/hyp/hyp-entry.S')
-rw-r--r-- | arch/arm/kvm/hyp/hyp-entry.S | 307 |
1 files changed, 307 insertions, 0 deletions
diff --git a/arch/arm/kvm/hyp/hyp-entry.S b/arch/arm/kvm/hyp/hyp-entry.S new file mode 100644 index 000000000..aa3f9a983 --- /dev/null +++ b/arch/arm/kvm/hyp/hyp-entry.S @@ -0,0 +1,307 @@ +/* + * Copyright (C) 2012 - Virtual Open Systems and Columbia University + * Author: Christoffer Dall <c.dall@virtualopensystems.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, write to the Free Software + * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + */ + +#include <linux/arm-smccc.h> +#include <linux/linkage.h> +#include <asm/kvm_arm.h> +#include <asm/kvm_asm.h> + + .arch_extension virt + + .text + .pushsection .hyp.text, "ax" + +.macro load_vcpu reg + mrc p15, 4, \reg, c13, c0, 2 @ HTPIDR +.endm + +/******************************************************************** + * Hypervisor exception vector and handlers + * + * + * The KVM/ARM Hypervisor ABI is defined as follows: + * + * Entry to Hyp mode from the host kernel will happen _only_ when an HVC + * instruction is issued since all traps are disabled when running the host + * kernel as per the Hyp-mode initialization at boot time. + * + * HVC instructions cause a trap to the vector page + offset 0x14 (see hyp_hvc + * below) when the HVC instruction is called from SVC mode (i.e. a guest or the + * host kernel) and they cause a trap to the vector page + offset 0x8 when HVC + * instructions are called from within Hyp-mode. + * + * Hyp-ABI: Calling HYP-mode functions from host (in SVC mode): + * Switching to Hyp mode is done through a simple HVC #0 instruction. The + * exception vector code will check that the HVC comes from VMID==0. + * - r0 contains a pointer to a HYP function + * - r1, r2, and r3 contain arguments to the above function. + * - The HYP function will be called with its arguments in r0, r1 and r2. + * On HYP function return, we return directly to SVC. + * + * Note that the above is used to execute code in Hyp-mode from a host-kernel + * point of view, and is a different concept from performing a world-switch and + * executing guest code SVC mode (with a VMID != 0). + */ + + .align 5 +__kvm_hyp_vector: + .global __kvm_hyp_vector + + @ Hyp-mode exception vector + W(b) hyp_reset + W(b) hyp_undef + W(b) hyp_svc + W(b) hyp_pabt + W(b) hyp_dabt + W(b) hyp_hvc + W(b) hyp_irq + W(b) hyp_fiq + +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR + .align 5 +__kvm_hyp_vector_ic_inv: + .global __kvm_hyp_vector_ic_inv + + /* + * We encode the exception entry in the bottom 3 bits of + * SP, and we have to guarantee to be 8 bytes aligned. + */ + W(add) sp, sp, #1 /* Reset 7 */ + W(add) sp, sp, #1 /* Undef 6 */ + W(add) sp, sp, #1 /* Syscall 5 */ + W(add) sp, sp, #1 /* Prefetch abort 4 */ + W(add) sp, sp, #1 /* Data abort 3 */ + W(add) sp, sp, #1 /* HVC 2 */ + W(add) sp, sp, #1 /* IRQ 1 */ + W(nop) /* FIQ 0 */ + + mcr p15, 0, r0, c7, c5, 0 /* ICIALLU */ + isb + + b decode_vectors + + .align 5 +__kvm_hyp_vector_bp_inv: + .global __kvm_hyp_vector_bp_inv + + /* + * We encode the exception entry in the bottom 3 bits of + * SP, and we have to guarantee to be 8 bytes aligned. + */ + W(add) sp, sp, #1 /* Reset 7 */ + W(add) sp, sp, #1 /* Undef 6 */ + W(add) sp, sp, #1 /* Syscall 5 */ + W(add) sp, sp, #1 /* Prefetch abort 4 */ + W(add) sp, sp, #1 /* Data abort 3 */ + W(add) sp, sp, #1 /* HVC 2 */ + W(add) sp, sp, #1 /* IRQ 1 */ + W(nop) /* FIQ 0 */ + + mcr p15, 0, r0, c7, c5, 6 /* BPIALL */ + isb + +decode_vectors: + +#ifdef CONFIG_THUMB2_KERNEL + /* + * Yet another silly hack: Use VPIDR as a temp register. + * Thumb2 is really a pain, as SP cannot be used with most + * of the bitwise instructions. The vect_br macro ensures + * things gets cleaned-up. + */ + mcr p15, 4, r0, c0, c0, 0 /* VPIDR */ + mov r0, sp + and r0, r0, #7 + sub sp, sp, r0 + push {r1, r2} + mov r1, r0 + mrc p15, 4, r0, c0, c0, 0 /* VPIDR */ + mrc p15, 0, r2, c0, c0, 0 /* MIDR */ + mcr p15, 4, r2, c0, c0, 0 /* VPIDR */ +#endif + +.macro vect_br val, targ +ARM( eor sp, sp, #\val ) +ARM( tst sp, #7 ) +ARM( eorne sp, sp, #\val ) + +THUMB( cmp r1, #\val ) +THUMB( popeq {r1, r2} ) + + beq \targ +.endm + + vect_br 0, hyp_fiq + vect_br 1, hyp_irq + vect_br 2, hyp_hvc + vect_br 3, hyp_dabt + vect_br 4, hyp_pabt + vect_br 5, hyp_svc + vect_br 6, hyp_undef + vect_br 7, hyp_reset +#endif + +.macro invalid_vector label, cause + .align +\label: mov r0, #\cause + b __hyp_panic +.endm + + invalid_vector hyp_reset ARM_EXCEPTION_RESET + invalid_vector hyp_undef ARM_EXCEPTION_UNDEFINED + invalid_vector hyp_svc ARM_EXCEPTION_SOFTWARE + invalid_vector hyp_pabt ARM_EXCEPTION_PREF_ABORT + invalid_vector hyp_fiq ARM_EXCEPTION_FIQ + +ENTRY(__hyp_do_panic) + mrs lr, cpsr + bic lr, lr, #MODE_MASK + orr lr, lr, #SVC_MODE +THUMB( orr lr, lr, #PSR_T_BIT ) + msr spsr_cxsf, lr + ldr lr, =panic + msr ELR_hyp, lr + ldr lr, =kvm_call_hyp + clrex + eret +ENDPROC(__hyp_do_panic) + +hyp_hvc: + /* + * Getting here is either because of a trap from a guest, + * or from executing HVC from the host kernel, which means + * "do something in Hyp mode". + */ + push {r0, r1, r2} + + @ Check syndrome register + mrc p15, 4, r1, c5, c2, 0 @ HSR + lsr r0, r1, #HSR_EC_SHIFT + cmp r0, #HSR_EC_HVC + bne guest_trap @ Not HVC instr. + + /* + * Let's check if the HVC came from VMID 0 and allow simple + * switch to Hyp mode + */ + mrrc p15, 6, r0, r2, c2 + lsr r2, r2, #16 + and r2, r2, #0xff + cmp r2, #0 + bne guest_hvc_trap @ Guest called HVC + + /* + * Getting here means host called HVC, we shift parameters and branch + * to Hyp function. + */ + pop {r0, r1, r2} + + /* + * Check if we have a kernel function, which is guaranteed to be + * bigger than the maximum hyp stub hypercall + */ + cmp r0, #HVC_STUB_HCALL_NR + bhs 1f + + /* + * Not a kernel function, treat it as a stub hypercall. + * Compute the physical address for __kvm_handle_stub_hvc + * (as the code lives in the idmaped page) and branch there. + * We hijack ip (r12) as a tmp register. + */ + push {r1} + ldr r1, =kimage_voffset + ldr r1, [r1] + ldr ip, =__kvm_handle_stub_hvc + sub ip, ip, r1 + pop {r1} + + bx ip + +1: + /* + * Pushing r2 here is just a way of keeping the stack aligned to + * 8 bytes on any path that can trigger a HYP exception. Here, + * we may well be about to jump into the guest, and the guest + * exit would otherwise be badly decoded by our fancy + * "decode-exception-without-a-branch" code... + */ + push {r2, lr} + + mov lr, r0 + mov r0, r1 + mov r1, r2 + mov r2, r3 + +THUMB( orr lr, #1) + blx lr @ Call the HYP function + + pop {r2, lr} + eret + +guest_hvc_trap: + movw r2, #:lower16:ARM_SMCCC_ARCH_WORKAROUND_1 + movt r2, #:upper16:ARM_SMCCC_ARCH_WORKAROUND_1 + ldr r0, [sp] @ Guest's r0 + teq r0, r2 + bne guest_trap + add sp, sp, #12 + @ Returns: + @ r0 = 0 + @ r1 = HSR value (perfectly predictable) + @ r2 = ARM_SMCCC_ARCH_WORKAROUND_1 + mov r0, #0 + eret + +guest_trap: + load_vcpu r0 @ Load VCPU pointer to r0 + +#ifdef CONFIG_VFPv3 + @ Check for a VFP access + lsr r1, r1, #HSR_EC_SHIFT + cmp r1, #HSR_EC_CP_0_13 + beq __vfp_guest_restore +#endif + + mov r1, #ARM_EXCEPTION_HVC + b __guest_exit + +hyp_irq: + push {r0, r1, r2} + mov r1, #ARM_EXCEPTION_IRQ + load_vcpu r0 @ Load VCPU pointer to r0 + b __guest_exit + +hyp_dabt: + push {r0, r1} + mrs r0, ELR_hyp + ldr r1, =abort_guest_exit_start +THUMB( add r1, r1, #1) + cmp r0, r1 + ldrne r1, =abort_guest_exit_end +THUMB( addne r1, r1, #1) + cmpne r0, r1 + pop {r0, r1} + bne __hyp_panic + + orr r0, r0, #(1 << ARM_EXIT_WITH_ABORT_BIT) + eret + + .ltorg + + .popsection |