arm64: KVM: HYP mode world switch implementation

The HYP mode world switch in all its glory.

Implements save/restore of host/guest registers, EL2 trapping,
IPA resolution, and additional services (tlb invalidation).

Reviewed-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 617 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
new file mode 100644
index 000000000000..0b18c2e1e043
--- /dev/null
+++ b/arch/arm64/kvm/hyp.S
@@ -0,0 +1,617 @@
+/*
+ * Copyright (C) 2012,2013 - 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/linkage.h>
+#include <linux/irqchip/arm-gic.h>
+
+#include <asm/assembler.h>
+#include <asm/memory.h>
+#include <asm/asm-offsets.h>
+#include <asm/fpsimdmacros.h>
+#include <asm/kvm.h>
+#include <asm/kvm_asm.h>
+#include <asm/kvm_arm.h>
+#include <asm/kvm_mmu.h>
+
+#define CPU_GP_REG_OFFSET(x)    (CPU_GP_REGS + x)
+#define CPU_XREG_OFFSET(x)      CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)
+#define CPU_SPSR_OFFSET(x)      CPU_GP_REG_OFFSET(CPU_SPSR + 8*x)
+#define CPU_SYSREG_OFFSET(x)    (CPU_SYSREGS + 8*x)
+
+        .text
+        .pushsection    .hyp.text, "ax"
+        .align  PAGE_SHIFT
+
+__kvm_hyp_code_start:
+        .globl __kvm_hyp_code_start
+
+.macro save_common_regs
+        // x2: base address for cpu context
+        // x3: tmp register
+
+        add     x3, x2, #CPU_XREG_OFFSET(19)
+        stp     x19, x20, [x3]
+        stp     x21, x22, [x3, #16]
+        stp     x23, x24, [x3, #32]
+        stp     x25, x26, [x3, #48]
+        stp     x27, x28, [x3, #64]
+        stp     x29, lr, [x3, #80]
+
+        mrs     x19, sp_el0
+        mrs     x20, elr_el2            // EL1 PC
+        mrs     x21, spsr_el2           // EL1 pstate
+
+        stp     x19, x20, [x3, #96]
+        str     x21, [x3, #112]
+
+        mrs     x22, sp_el1
+        mrs     x23, elr_el1
+        mrs     x24, spsr_el1
+
+        str     x22, [x2, #CPU_GP_REG_OFFSET(CPU_SP_EL1)]
+        str     x23, [x2, #CPU_GP_REG_OFFSET(CPU_ELR_EL1)]
+        str     x24, [x2, #CPU_SPSR_OFFSET(KVM_SPSR_EL1)]
+.endm
+
+.macro restore_common_regs
+        // x2: base address for cpu context
+        // x3: tmp register
+
+        ldr     x22, [x2, #CPU_GP_REG_OFFSET(CPU_SP_EL1)]
+        ldr     x23, [x2, #CPU_GP_REG_OFFSET(CPU_ELR_EL1)]
+        ldr     x24, [x2, #CPU_SPSR_OFFSET(KVM_SPSR_EL1)]
+
+        msr     sp_el1, x22
+        msr     elr_el1, x23
+        msr     spsr_el1, x24
+
+        add     x3, x2, #CPU_XREG_OFFSET(31)    // SP_EL0
+        ldp     x19, x20, [x3]
+        ldr     x21, [x3, #16]
+
+        msr     sp_el0, x19
+        msr     elr_el2, x20                            // EL1 PC
+        msr     spsr_el2, x21                           // EL1 pstate
+
+        add     x3, x2, #CPU_XREG_OFFSET(19)
+        ldp     x19, x20, [x3]
+        ldp     x21, x22, [x3, #16]
+        ldp     x23, x24, [x3, #32]
+        ldp     x25, x26, [x3, #48]
+        ldp     x27, x28, [x3, #64]
+        ldp     x29, lr, [x3, #80]
+.endm
+
+.macro save_host_regs
+        save_common_regs
+.endm
+
+.macro restore_host_regs
+        restore_common_regs
+.endm
+
+.macro save_fpsimd
+        // x2: cpu context address
+        // x3, x4: tmp regs
+        add     x3, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
+        fpsimd_save x3, 4
+.endm
+
+.macro restore_fpsimd
+        // x2: cpu context address
+        // x3, x4: tmp regs
+        add     x3, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
+        fpsimd_restore x3, 4
+.endm
+
+.macro save_guest_regs
+        // x0 is the vcpu address
+        // x1 is the return code, do not corrupt!
+        // x2 is the cpu context
+        // x3 is a tmp register
+        // Guest's x0-x3 are on the stack
+
+        // Compute base to save registers
+        add     x3, x2, #CPU_XREG_OFFSET(4)
+        stp     x4, x5, [x3]
+        stp     x6, x7, [x3, #16]
+        stp     x8, x9, [x3, #32]
+        stp     x10, x11, [x3, #48]
+        stp     x12, x13, [x3, #64]
+        stp     x14, x15, [x3, #80]
+        stp     x16, x17, [x3, #96]
+        str     x18, [x3, #112]
+
+        pop     x6, x7                  // x2, x3
+        pop     x4, x5                  // x0, x1
+
+        add     x3, x2, #CPU_XREG_OFFSET(0)
+        stp     x4, x5, [x3]
+        stp     x6, x7, [x3, #16]
+
+        save_common_regs
+.endm
+
+.macro restore_guest_regs
+        // x0 is the vcpu address.
+        // x2 is the cpu context
+        // x3 is a tmp register
+
+        // Prepare x0-x3 for later restore
+        add     x3, x2, #CPU_XREG_OFFSET(0)
+        ldp     x4, x5, [x3]
+        ldp     x6, x7, [x3, #16]
+        push    x4, x5          // Push x0-x3 on the stack
+        push    x6, x7
+
+        // x4-x18
+        ldp     x4, x5, [x3, #32]
+        ldp     x6, x7, [x3, #48]
+        ldp     x8, x9, [x3, #64]
+        ldp     x10, x11, [x3, #80]
+        ldp     x12, x13, [x3, #96]
+        ldp     x14, x15, [x3, #112]
+        ldp     x16, x17, [x3, #128]
+        ldr     x18, [x3, #144]
+
+        // x19-x29, lr, sp*, elr*, spsr*
+        restore_common_regs
+
+        // Last bits of the 64bit state
+        pop     x2, x3
+        pop     x0, x1
+
+        // Do not touch any register after this!
+.endm
+
+/*
+ * Macros to perform system register save/restore.
+ *
+ * Ordering here is absolutely critical, and must be kept consistent
+ * in {save,restore}_sysregs, {save,restore}_guest_32bit_state,
+ * and in kvm_asm.h.
+ *
+ * In other words, don't touch any of these unless you know what
+ * you are doing.
+ */
+.macro save_sysregs
+        // x2: base address for cpu context
+        // x3: tmp register
+
+        add     x3, x2, #CPU_SYSREG_OFFSET(MPIDR_EL1)
+
+        mrs     x4,     vmpidr_el2
+        mrs     x5,     csselr_el1
+        mrs     x6,     sctlr_el1
+        mrs     x7,     actlr_el1
+        mrs     x8,     cpacr_el1
+        mrs     x9,     ttbr0_el1
+        mrs     x10,    ttbr1_el1
+        mrs     x11,    tcr_el1
+        mrs     x12,    esr_el1
+        mrs     x13,    afsr0_el1
+        mrs     x14,    afsr1_el1
+        mrs     x15,    far_el1
+        mrs     x16,    mair_el1
+        mrs     x17,    vbar_el1
+        mrs     x18,    contextidr_el1
+        mrs     x19,    tpidr_el0
+        mrs     x20,    tpidrro_el0
+        mrs     x21,    tpidr_el1
+        mrs     x22,    amair_el1
+        mrs     x23,    cntkctl_el1
+
+        stp     x4, x5, [x3]
+        stp     x6, x7, [x3, #16]
+        stp     x8, x9, [x3, #32]
+        stp     x10, x11, [x3, #48]
+        stp     x12, x13, [x3, #64]
+        stp     x14, x15, [x3, #80]
+        stp     x16, x17, [x3, #96]
+        stp     x18, x19, [x3, #112]
+        stp     x20, x21, [x3, #128]
+        stp     x22, x23, [x3, #144]
+.endm
+
+.macro restore_sysregs
+        // x2: base address for cpu context
+        // x3: tmp register
+
+        add     x3, x2, #CPU_SYSREG_OFFSET(MPIDR_EL1)
+
+        ldp     x4, x5, [x3]
+        ldp     x6, x7, [x3, #16]
+        ldp     x8, x9, [x3, #32]
+        ldp     x10, x11, [x3, #48]
+        ldp     x12, x13, [x3, #64]
+        ldp     x14, x15, [x3, #80]
+        ldp     x16, x17, [x3, #96]
+        ldp     x18, x19, [x3, #112]
+        ldp     x20, x21, [x3, #128]
+        ldp     x22, x23, [x3, #144]
+
+        msr     vmpidr_el2,     x4
+        msr     csselr_el1,     x5
+        msr     sctlr_el1,      x6
+        msr     actlr_el1,      x7
+        msr     cpacr_el1,      x8
+        msr     ttbr0_el1,      x9
+        msr     ttbr1_el1,      x10
+        msr     tcr_el1,        x11
+        msr     esr_el1,        x12
+        msr     afsr0_el1,      x13
+        msr     afsr1_el1,      x14
+        msr     far_el1,        x15
+        msr     mair_el1,       x16
+        msr     vbar_el1,       x17
+        msr     contextidr_el1, x18
+        msr     tpidr_el0,      x19
+        msr     tpidrro_el0,    x20
+        msr     tpidr_el1,      x21
+        msr     amair_el1,      x22
+        msr     cntkctl_el1,    x23
+.endm
+
+.macro activate_traps
+        ldr     x2, [x0, #VCPU_IRQ_LINES]
+        ldr     x1, [x0, #VCPU_HCR_EL2]
+        orr     x2, x2, x1
+        msr     hcr_el2, x2
+
+        ldr     x2, =(CPTR_EL2_TTA)
+        msr     cptr_el2, x2
+
+        ldr     x2, =(1 << 15)  // Trap CP15 Cr=15
+        msr     hstr_el2, x2
+
+        mrs     x2, mdcr_el2
+        and     x2, x2, #MDCR_EL2_HPMN_MASK
+        orr     x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
+        msr     mdcr_el2, x2
+.endm
+
+.macro deactivate_traps
+        mov     x2, #HCR_RW
+        msr     hcr_el2, x2
+        msr     cptr_el2, xzr
+        msr     hstr_el2, xzr
+
+        mrs     x2, mdcr_el2
+        and     x2, x2, #MDCR_EL2_HPMN_MASK
+        msr     mdcr_el2, x2
+.endm
+
+.macro activate_vm
+        ldr     x1, [x0, #VCPU_KVM]
+        kern_hyp_va     x1
+        ldr     x2, [x1, #KVM_VTTBR]
+        msr     vttbr_el2, x2
+.endm
+
+.macro deactivate_vm
+        msr     vttbr_el2, xzr
+.endm
+
+__save_sysregs:
+        save_sysregs
+        ret
+
+__restore_sysregs:
+        restore_sysregs
+        ret
+
+__save_fpsimd:
+        save_fpsimd
+        ret
+
+__restore_fpsimd:
+        restore_fpsimd
+        ret
+
+/*
+ * u64 __kvm_vcpu_run(struct kvm_vcpu *vcpu);
+ *
+ * This is the world switch. The first half of the function
+ * deals with entering the guest, and anything from __kvm_vcpu_return
+ * to the end of the function deals with reentering the host.
+ * On the enter path, only x0 (vcpu pointer) must be preserved until
+ * the last moment. On the exit path, x0 (vcpu pointer) and x1 (exception
+ * code) must both be preserved until the epilogue.
+ * In both cases, x2 points to the CPU context we're saving/restoring from/to.
+ */
+ENTRY(__kvm_vcpu_run)
+        kern_hyp_va     x0
+        msr     tpidr_el2, x0   // Save the vcpu register
+
+        // Host context
+        ldr     x2, [x0, #VCPU_HOST_CONTEXT]
+        kern_hyp_va x2
+
+        save_host_regs
+        bl __save_fpsimd
+        bl __save_sysregs
+
+        activate_traps
+        activate_vm
+
+        // Guest context
+        add     x2, x0, #VCPU_CONTEXT
+
+        bl __restore_sysregs
+        bl __restore_fpsimd
+        restore_guest_regs
+
+        // That's it, no more messing around.
+        eret
+
+__kvm_vcpu_return:
+        // Assume x0 is the vcpu pointer, x1 the return code
+        // Guest's x0-x3 are on the stack
+
+        // Guest context
+        add     x2, x0, #VCPU_CONTEXT
+
+        save_guest_regs
+        bl __save_fpsimd
+        bl __save_sysregs
+
+        deactivate_traps
+        deactivate_vm
+
+        // Host context
+        ldr     x2, [x0, #VCPU_HOST_CONTEXT]
+        kern_hyp_va x2
+
+        bl __restore_sysregs
+        bl __restore_fpsimd
+        restore_host_regs
+
+        mov     x0, x1
+        ret
+END(__kvm_vcpu_run)
+
+// void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
+ENTRY(__kvm_tlb_flush_vmid_ipa)
+        kern_hyp_va     x0
+        ldr     x2, [x0, #KVM_VTTBR]
+        msr     vttbr_el2, x2
+        isb
+
+        /*
+         * We could do so much better if we had the VA as well.
+         * Instead, we invalidate Stage-2 for this IPA, and the
+         * whole of Stage-1. Weep...
+         */
+        tlbi    ipas2e1is, x1
+        dsb     sy
+        tlbi    vmalle1is
+        dsb     sy
+        isb
+
+        msr     vttbr_el2, xzr
+        ret
+ENDPROC(__kvm_tlb_flush_vmid_ipa)
+
+ENTRY(__kvm_flush_vm_context)
+        tlbi    alle1is
+        ic      ialluis
+        dsb     sy
+        ret
+ENDPROC(__kvm_flush_vm_context)
+
+__kvm_hyp_panic:
+        // Guess the context by looking at VTTBR:
+        // If zero, then we're already a host.
+        // Otherwise restore a minimal host context before panicing.
+        mrs     x0, vttbr_el2
+        cbz     x0, 1f
+
+        mrs     x0, tpidr_el2
+
+        deactivate_traps
+        deactivate_vm
+
+        ldr     x2, [x0, #VCPU_HOST_CONTEXT]
+        kern_hyp_va x2
+
+        bl __restore_sysregs
+
+1:      adr     x0, __hyp_panic_str
+        adr     x1, 2f
+        ldp     x2, x3, [x1]
+        sub     x0, x0, x2
+        add     x0, x0, x3
+        mrs     x1, spsr_el2
+        mrs     x2, elr_el2
+        mrs     x3, esr_el2
+        mrs     x4, far_el2
+        mrs     x5, hpfar_el2
+        mrs     x6, par_el1
+        mrs     x7, tpidr_el2
+
+        mov     lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
+                      PSR_MODE_EL1h)
+        msr     spsr_el2, lr
+        ldr     lr, =panic
+        msr     elr_el2, lr
+        eret
+
+        .align  3
+2:      .quad   HYP_PAGE_OFFSET
+        .quad   PAGE_OFFSET
+ENDPROC(__kvm_hyp_panic)
+
+__hyp_panic_str:
+        .ascii  "HYP panic:\nPS:%08x PC:%p ESR:%p\nFAR:%p HPFAR:%p PAR:%p\nVCPU:%p\n\0"
+
+        .align  2
+
+ENTRY(kvm_call_hyp)
+        hvc     #0
+        ret
+ENDPROC(kvm_call_hyp)
+
+.macro invalid_vector   label, target
+        .align  2
+\label:
+        b \target
+ENDPROC(\label)
+.endm
+
+        /* None of these should ever happen */
+        invalid_vector  el2t_sync_invalid, __kvm_hyp_panic
+        invalid_vector  el2t_irq_invalid, __kvm_hyp_panic
+        invalid_vector  el2t_fiq_invalid, __kvm_hyp_panic
+        invalid_vector  el2t_error_invalid, __kvm_hyp_panic
+        invalid_vector  el2h_sync_invalid, __kvm_hyp_panic
+        invalid_vector  el2h_irq_invalid, __kvm_hyp_panic
+        invalid_vector  el2h_fiq_invalid, __kvm_hyp_panic
+        invalid_vector  el2h_error_invalid, __kvm_hyp_panic
+        invalid_vector  el1_sync_invalid, __kvm_hyp_panic
+        invalid_vector  el1_irq_invalid, __kvm_hyp_panic
+        invalid_vector  el1_fiq_invalid, __kvm_hyp_panic
+        invalid_vector  el1_error_invalid, __kvm_hyp_panic
+
+el1_sync:                                       // Guest trapped into EL2
+        push    x0, x1
+        push    x2, x3
+
+        mrs     x1, esr_el2
+        lsr     x2, x1, #ESR_EL2_EC_SHIFT
+
+        cmp     x2, #ESR_EL2_EC_HVC64
+        b.ne    el1_trap
+
+        mrs     x3, vttbr_el2                   // If vttbr is valid, the 64bit guest
+        cbnz    x3, el1_trap                    // called HVC
+
+        /* Here, we're pretty sure the host called HVC. */
+        pop     x2, x3
+        pop     x0, x1
+
+        push    lr, xzr
+
+        /*
+         * Compute the function address in EL2, and shuffle the parameters.
+         */
+        kern_hyp_va     x0
+        mov     lr, x0
+        mov     x0, x1
+        mov     x1, x2
+        mov     x2, x3
+        blr     lr
+
+        pop     lr, xzr
+        eret
+
+el1_trap:
+        /*
+         * x1: ESR
+         * x2: ESR_EC
+         */
+        cmp     x2, #ESR_EL2_EC_DABT
+        mov     x0, #ESR_EL2_EC_IABT
+        ccmp    x2, x0, #4, ne
+        b.ne    1f              // Not an abort we care about
+
+        /* This is an abort. Check for permission fault */
+        and     x2, x1, #ESR_EL2_FSC_TYPE
+        cmp     x2, #FSC_PERM
+        b.ne    1f              // Not a permission fault
+
+        /*
+         * Check for Stage-1 page table walk, which is guaranteed
+         * to give a valid HPFAR_EL2.
+         */
+        tbnz    x1, #7, 1f      // S1PTW is set
+
+        /*
+         * Permission fault, HPFAR_EL2 is invalid.
+         * Resolve the IPA the hard way using the guest VA.
+         * Stage-1 translation already validated the memory access rights.
+         * As such, we can use the EL1 translation regime, and don't have
+         * to distinguish between EL0 and EL1 access.
+         */
+        mrs     x2, far_el2
+        at      s1e1r, x2
+        isb
+
+        /* Read result */
+        mrs     x3, par_el1
+        tbnz    x3, #0, 3f              // Bail out if we failed the translation
+        ubfx    x3, x3, #12, #36        // Extract IPA
+        lsl     x3, x3, #4              // and present it like HPFAR
+        b       2f
+
+1:      mrs     x3, hpfar_el2
+        mrs     x2, far_el2
+
+2:      mrs     x0, tpidr_el2
+        str     x1, [x0, #VCPU_ESR_EL2]
+        str     x2, [x0, #VCPU_FAR_EL2]
+        str     x3, [x0, #VCPU_HPFAR_EL2]
+
+        mov     x1, #ARM_EXCEPTION_TRAP
+        b       __kvm_vcpu_return
+
+        /*
+         * Translation failed. Just return to the guest and
+         * let it fault again. Another CPU is probably playing
+         * behind our back.
+         */
+3:      pop     x2, x3
+        pop     x0, x1
+
+        eret
+
+el1_irq:
+        push    x0, x1
+        push    x2, x3
+        mrs     x0, tpidr_el2
+        mov     x1, #ARM_EXCEPTION_IRQ
+        b       __kvm_vcpu_return
+
+        .ltorg
+
+        .align 11
+
+ENTRY(__kvm_hyp_vector)
+        ventry  el2t_sync_invalid               // Synchronous EL2t
+        ventry  el2t_irq_invalid                // IRQ EL2t
+        ventry  el2t_fiq_invalid                // FIQ EL2t
+        ventry  el2t_error_invalid              // Error EL2t
+
+        ventry  el2h_sync_invalid               // Synchronous EL2h
+        ventry  el2h_irq_invalid                // IRQ EL2h
+        ventry  el2h_fiq_invalid                // FIQ EL2h
+        ventry  el2h_error_invalid              // Error EL2h
+
+        ventry  el1_sync                        // Synchronous 64-bit EL1
+        ventry  el1_irq                         // IRQ 64-bit EL1
+        ventry  el1_fiq_invalid                 // FIQ 64-bit EL1
+        ventry  el1_error_invalid               // Error 64-bit EL1
+
+        ventry  el1_sync                        // Synchronous 32-bit EL1
+        ventry  el1_irq                         // IRQ 32-bit EL1
+        ventry  el1_fiq_invalid                 // FIQ 32-bit EL1
+        ventry  el1_error_invalid               // Error 32-bit EL1
+ENDPROC(__kvm_hyp_vector)
+
+__kvm_hyp_code_end:
+        .globl  __kvm_hyp_code_end
+
+        .popsection