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Diffstat (limited to 'arch/mips/kvm/entry.c')
| -rw-r--r-- | arch/mips/kvm/entry.c | 701 |
1 files changed, 701 insertions, 0 deletions
diff --git a/arch/mips/kvm/entry.c b/arch/mips/kvm/entry.c new file mode 100644 index 000000000000..6a02b3a3fa65 --- /dev/null +++ b/arch/mips/kvm/entry.c @@ -0,0 +1,701 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Generation of main entry point for the guest, exception handling. + * + * Copyright (C) 2012 MIPS Technologies, Inc. + * Authors: Sanjay Lal <sanjayl@kymasys.com> + * + * Copyright (C) 2016 Imagination Technologies Ltd. + */ + +#include <linux/kvm_host.h> +#include <asm/msa.h> +#include <asm/setup.h> +#include <asm/uasm.h> + +/* Register names */ +#define ZERO 0 +#define AT 1 +#define V0 2 +#define V1 3 +#define A0 4 +#define A1 5 + +#if _MIPS_SIM == _MIPS_SIM_ABI32 +#define T0 8 +#define T1 9 +#define T2 10 +#define T3 11 +#endif /* _MIPS_SIM == _MIPS_SIM_ABI32 */ + +#if _MIPS_SIM == _MIPS_SIM_ABI64 || _MIPS_SIM == _MIPS_SIM_NABI32 +#define T0 12 +#define T1 13 +#define T2 14 +#define T3 15 +#endif /* _MIPS_SIM == _MIPS_SIM_ABI64 || _MIPS_SIM == _MIPS_SIM_NABI32 */ + +#define S0 16 +#define S1 17 +#define T9 25 +#define K0 26 +#define K1 27 +#define GP 28 +#define SP 29 +#define RA 31 + +/* Some CP0 registers */ +#define C0_HWRENA 7, 0 +#define C0_BADVADDR 8, 0 +#define C0_ENTRYHI 10, 0 +#define C0_STATUS 12, 0 +#define C0_CAUSE 13, 0 +#define C0_EPC 14, 0 +#define C0_EBASE 15, 1 +#define C0_CONFIG5 16, 5 +#define C0_DDATA_LO 28, 3 +#define C0_ERROREPC 30, 0 + +#define CALLFRAME_SIZ 32 + +#ifdef CONFIG_64BIT +#define ST0_KX_IF_64 ST0_KX +#else +#define ST0_KX_IF_64 0 +#endif + +static unsigned int scratch_vcpu[2] = { C0_DDATA_LO }; +static unsigned int scratch_tmp[2] = { C0_ERROREPC }; + +enum label_id { + label_fpu_1 = 1, + label_msa_1, + label_return_to_host, + label_kernel_asid, + label_exit_common, +}; + +UASM_L_LA(_fpu_1) +UASM_L_LA(_msa_1) +UASM_L_LA(_return_to_host) +UASM_L_LA(_kernel_asid) +UASM_L_LA(_exit_common) + +static void *kvm_mips_build_enter_guest(void *addr); +static void *kvm_mips_build_ret_from_exit(void *addr); +static void *kvm_mips_build_ret_to_guest(void *addr); +static void *kvm_mips_build_ret_to_host(void *addr); + +/** + * kvm_mips_entry_setup() - Perform global setup for entry code. + * + * Perform global setup for entry code, such as choosing a scratch register. + * + * Returns: 0 on success. + * -errno on failure. + */ +int kvm_mips_entry_setup(void) +{ + /* + * We prefer to use KScratchN registers if they are available over the + * defaults above, which may not work on all cores. + */ + unsigned int kscratch_mask = cpu_data[0].kscratch_mask & 0xfc; + + /* Pick a scratch register for storing VCPU */ + if (kscratch_mask) { + scratch_vcpu[0] = 31; + scratch_vcpu[1] = ffs(kscratch_mask) - 1; + kscratch_mask &= ~BIT(scratch_vcpu[1]); + } + + /* Pick a scratch register to use as a temp for saving state */ + if (kscratch_mask) { + scratch_tmp[0] = 31; + scratch_tmp[1] = ffs(kscratch_mask) - 1; + kscratch_mask &= ~BIT(scratch_tmp[1]); + } + + return 0; +} + +static void kvm_mips_build_save_scratch(u32 **p, unsigned int tmp, + unsigned int frame) +{ + /* Save the VCPU scratch register value in cp0_epc of the stack frame */ + UASM_i_MFC0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]); + UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame); + + /* Save the temp scratch register value in cp0_cause of stack frame */ + if (scratch_tmp[0] == 31) { + UASM_i_MFC0(p, tmp, scratch_tmp[0], scratch_tmp[1]); + UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame); + } +} + +static void kvm_mips_build_restore_scratch(u32 **p, unsigned int tmp, + unsigned int frame) +{ + /* + * Restore host scratch register values saved by + * kvm_mips_build_save_scratch(). + */ + UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame); + UASM_i_MTC0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]); + + if (scratch_tmp[0] == 31) { + UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame); + UASM_i_MTC0(p, tmp, scratch_tmp[0], scratch_tmp[1]); + } +} + +/** + * build_set_exc_base() - Assemble code to write exception base address. + * @p: Code buffer pointer. + * @reg: Source register (generated code may set WG bit in @reg). + * + * Assemble code to modify the exception base address in the EBase register, + * using the appropriately sized access and setting the WG bit if necessary. + */ +static inline void build_set_exc_base(u32 **p, unsigned int reg) +{ + if (cpu_has_ebase_wg) { + /* Set WG so that all the bits get written */ + uasm_i_ori(p, reg, reg, MIPS_EBASE_WG); + UASM_i_MTC0(p, reg, C0_EBASE); + } else { + uasm_i_mtc0(p, reg, C0_EBASE); + } +} + +/** + * kvm_mips_build_vcpu_run() - Assemble function to start running a guest VCPU. + * @addr: Address to start writing code. + * + * Assemble the start of the vcpu_run function to run a guest VCPU. The function + * conforms to the following prototype: + * + * int vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu); + * + * The exit from the guest and return to the caller is handled by the code + * generated by kvm_mips_build_ret_to_host(). + * + * Returns: Next address after end of written function. + */ +void *kvm_mips_build_vcpu_run(void *addr) +{ + u32 *p = addr; + unsigned int i; + + /* + * A0: run + * A1: vcpu + */ + + /* k0/k1 not being used in host kernel context */ + UASM_i_ADDIU(&p, K1, SP, -(int)sizeof(struct pt_regs)); + for (i = 16; i < 32; ++i) { + if (i == 24) + i = 28; + UASM_i_SW(&p, i, offsetof(struct pt_regs, regs[i]), K1); + } + + /* Save host status */ + uasm_i_mfc0(&p, V0, C0_STATUS); + UASM_i_SW(&p, V0, offsetof(struct pt_regs, cp0_status), K1); + + /* Save scratch registers, will be used to store pointer to vcpu etc */ + kvm_mips_build_save_scratch(&p, V1, K1); + + /* VCPU scratch register has pointer to vcpu */ + UASM_i_MTC0(&p, A1, scratch_vcpu[0], scratch_vcpu[1]); + + /* Offset into vcpu->arch */ + UASM_i_ADDIU(&p, K1, A1, offsetof(struct kvm_vcpu, arch)); + + /* + * Save the host stack to VCPU, used for exception processing + * when we exit from the Guest + */ + UASM_i_SW(&p, SP, offsetof(struct kvm_vcpu_arch, host_stack), K1); + + /* Save the kernel gp as well */ + UASM_i_SW(&p, GP, offsetof(struct kvm_vcpu_arch, host_gp), K1); + + /* + * Setup status register for running the guest in UM, interrupts + * are disabled + */ + UASM_i_LA(&p, K0, ST0_EXL | KSU_USER | ST0_BEV | ST0_KX_IF_64); + uasm_i_mtc0(&p, K0, C0_STATUS); + uasm_i_ehb(&p); + + /* load up the new EBASE */ + UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, guest_ebase), K1); + build_set_exc_base(&p, K0); + + /* + * Now that the new EBASE has been loaded, unset BEV, set + * interrupt mask as it was but make sure that timer interrupts + * are enabled + */ + uasm_i_addiu(&p, K0, ZERO, ST0_EXL | KSU_USER | ST0_IE | ST0_KX_IF_64); + uasm_i_andi(&p, V0, V0, ST0_IM); + uasm_i_or(&p, K0, K0, V0); + uasm_i_mtc0(&p, K0, C0_STATUS); + uasm_i_ehb(&p); + + p = kvm_mips_build_enter_guest(p); + + return p; +} + +/** + * kvm_mips_build_enter_guest() - Assemble code to resume guest execution. + * @addr: Address to start writing code. + * + * Assemble the code to resume guest execution. This code is common between the + * initial entry into the guest from the host, and returning from the exit + * handler back to the guest. + * + * Returns: Next address after end of written function. + */ +static void *kvm_mips_build_enter_guest(void *addr) +{ + u32 *p = addr; + unsigned int i; + struct uasm_label labels[2]; + struct uasm_reloc relocs[2]; + struct uasm_label *l = labels; + struct uasm_reloc *r = relocs; + + memset(labels, 0, sizeof(labels)); + memset(relocs, 0, sizeof(relocs)); + + /* Set Guest EPC */ + UASM_i_LW(&p, T0, offsetof(struct kvm_vcpu_arch, pc), K1); + UASM_i_MTC0(&p, T0, C0_EPC); + + /* Set the ASID for the Guest Kernel */ + UASM_i_LW(&p, T0, offsetof(struct kvm_vcpu_arch, cop0), K1); + UASM_i_LW(&p, T0, offsetof(struct mips_coproc, reg[MIPS_CP0_STATUS][0]), + T0); + uasm_i_andi(&p, T0, T0, KSU_USER | ST0_ERL | ST0_EXL); + uasm_i_xori(&p, T0, T0, KSU_USER); + uasm_il_bnez(&p, &r, T0, label_kernel_asid); + UASM_i_ADDIU(&p, T1, K1, + offsetof(struct kvm_vcpu_arch, guest_kernel_asid)); + /* else user */ + UASM_i_ADDIU(&p, T1, K1, + offsetof(struct kvm_vcpu_arch, guest_user_asid)); + uasm_l_kernel_asid(&l, p); + + /* t1: contains the base of the ASID array, need to get the cpu id */ + /* smp_processor_id */ + uasm_i_lw(&p, T2, offsetof(struct thread_info, cpu), GP); + /* x4 */ + uasm_i_sll(&p, T2, T2, 2); + UASM_i_ADDU(&p, T3, T1, T2); + uasm_i_lw(&p, K0, 0, T3); +#ifdef CONFIG_MIPS_ASID_BITS_VARIABLE + /* x sizeof(struct cpuinfo_mips)/4 */ + uasm_i_addiu(&p, T3, ZERO, sizeof(struct cpuinfo_mips)/4); + uasm_i_mul(&p, T2, T2, T3); + + UASM_i_LA_mostly(&p, AT, (long)&cpu_data[0].asid_mask); + UASM_i_ADDU(&p, AT, AT, T2); + UASM_i_LW(&p, T2, uasm_rel_lo((long)&cpu_data[0].asid_mask), AT); + uasm_i_and(&p, K0, K0, T2); +#else + uasm_i_andi(&p, K0, K0, MIPS_ENTRYHI_ASID); +#endif + uasm_i_mtc0(&p, K0, C0_ENTRYHI); + uasm_i_ehb(&p); + + /* Disable RDHWR access */ + uasm_i_mtc0(&p, ZERO, C0_HWRENA); + + /* load the guest context from VCPU and return */ + for (i = 1; i < 32; ++i) { + /* Guest k0/k1 loaded later */ + if (i == K0 || i == K1) + continue; + UASM_i_LW(&p, i, offsetof(struct kvm_vcpu_arch, gprs[i]), K1); + } + +#ifndef CONFIG_CPU_MIPSR6 + /* Restore hi/lo */ + UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, hi), K1); + uasm_i_mthi(&p, K0); + + UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, lo), K1); + uasm_i_mtlo(&p, K0); +#endif + + /* Restore the guest's k0/k1 registers */ + UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, gprs[K0]), K1); + UASM_i_LW(&p, K1, offsetof(struct kvm_vcpu_arch, gprs[K1]), K1); + + /* Jump to guest */ + uasm_i_eret(&p); + + uasm_resolve_relocs(relocs, labels); + + return p; +} + +/** + * kvm_mips_build_exception() - Assemble first level guest exception handler. + * @addr: Address to start writing code. + * @handler: Address of common handler (within range of @addr). + * + * Assemble exception vector code for guest execution. The generated vector will + * branch to the common exception handler generated by kvm_mips_build_exit(). + * + * Returns: Next address after end of written function. + */ +void *kvm_mips_build_exception(void *addr, void *handler) +{ + u32 *p = addr; + struct uasm_label labels[2]; + struct uasm_reloc relocs[2]; + struct uasm_label *l = labels; + struct uasm_reloc *r = relocs; + + memset(labels, 0, sizeof(labels)); + memset(relocs, 0, sizeof(relocs)); + + /* Save guest k1 into scratch register */ + UASM_i_MTC0(&p, K1, scratch_tmp[0], scratch_tmp[1]); + + /* Get the VCPU pointer from the VCPU scratch register */ + UASM_i_MFC0(&p, K1, scratch_vcpu[0], scratch_vcpu[1]); + UASM_i_ADDIU(&p, K1, K1, offsetof(struct kvm_vcpu, arch)); + + /* Save guest k0 into VCPU structure */ + UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, gprs[K0]), K1); + + /* Branch to the common handler */ + uasm_il_b(&p, &r, label_exit_common); + uasm_i_nop(&p); + + uasm_l_exit_common(&l, handler); + uasm_resolve_relocs(relocs, labels); + + return p; +} + +/** + * kvm_mips_build_exit() - Assemble common guest exit handler. + * @addr: Address to start writing code. + * + * Assemble the generic guest exit handling code. This is called by the + * exception vectors (generated by kvm_mips_build_exception()), and calls + * kvm_mips_handle_exit(), then either resumes the guest or returns to the host + * depending on the return value. + * + * Returns: Next address after end of written function. + */ +void *kvm_mips_build_exit(void *addr) +{ + u32 *p = addr; + unsigned int i; + struct uasm_label labels[3]; + struct uasm_reloc relocs[3]; + struct uasm_label *l = labels; + struct uasm_reloc *r = relocs; + + memset(labels, 0, sizeof(labels)); + memset(relocs, 0, sizeof(relocs)); + + /* + * Generic Guest exception handler. We end up here when the guest + * does something that causes a trap to kernel mode. + * + * Both k0/k1 registers will have already been saved (k0 into the vcpu + * structure, and k1 into the scratch_tmp register). + * + * The k1 register will already contain the kvm_vcpu_arch pointer. + */ + + /* Start saving Guest context to VCPU */ + for (i = 0; i < 32; ++i) { + /* Guest k0/k1 saved later */ + if (i == K0 || i == K1) + continue; + UASM_i_SW(&p, i, offsetof(struct kvm_vcpu_arch, gprs[i]), K1); + } + +#ifndef CONFIG_CPU_MIPSR6 + /* We need to save hi/lo and restore them on the way out */ + uasm_i_mfhi(&p, T0); + UASM_i_SW(&p, T0, offsetof(struct kvm_vcpu_arch, hi), K1); + + uasm_i_mflo(&p, T0); + UASM_i_SW(&p, T0, offsetof(struct kvm_vcpu_arch, lo), K1); +#endif + + /* Finally save guest k1 to VCPU */ + uasm_i_ehb(&p); + UASM_i_MFC0(&p, T0, scratch_tmp[0], scratch_tmp[1]); + UASM_i_SW(&p, T0, offsetof(struct kvm_vcpu_arch, gprs[K1]), K1); + + /* Now that context has been saved, we can use other registers */ + + /* Restore vcpu */ + UASM_i_MFC0(&p, A1, scratch_vcpu[0], scratch_vcpu[1]); + uasm_i_move(&p, S1, A1); + + /* Restore run (vcpu->run) */ + UASM_i_LW(&p, A0, offsetof(struct kvm_vcpu, run), A1); + /* Save pointer to run in s0, will be saved by the compiler */ + uasm_i_move(&p, S0, A0); + + /* + * Save Host level EPC, BadVaddr and Cause to VCPU, useful to process + * the exception + */ + UASM_i_MFC0(&p, K0, C0_EPC); + UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, pc), K1); + + UASM_i_MFC0(&p, K0, C0_BADVADDR); + UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, host_cp0_badvaddr), + K1); + + uasm_i_mfc0(&p, K0, C0_CAUSE); + uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch, host_cp0_cause), K1); + + /* Now restore the host state just enough to run the handlers */ + + /* Switch EBASE to the one used by Linux */ + /* load up the host EBASE */ + uasm_i_mfc0(&p, V0, C0_STATUS); + + uasm_i_lui(&p, AT, ST0_BEV >> 16); + uasm_i_or(&p, K0, V0, AT); + + uasm_i_mtc0(&p, K0, C0_STATUS); + uasm_i_ehb(&p); + + UASM_i_LA_mostly(&p, K0, (long)&ebase); + UASM_i_LW(&p, K0, uasm_rel_lo((long)&ebase), K0); + build_set_exc_base(&p, K0); + + if (raw_cpu_has_fpu) { + /* + * If FPU is enabled, save FCR31 and clear it so that later + * ctc1's don't trigger FPE for pending exceptions. + */ + uasm_i_lui(&p, AT, ST0_CU1 >> 16); + uasm_i_and(&p, V1, V0, AT); + uasm_il_beqz(&p, &r, V1, label_fpu_1); + uasm_i_nop(&p); + uasm_i_cfc1(&p, T0, 31); + uasm_i_sw(&p, T0, offsetof(struct kvm_vcpu_arch, fpu.fcr31), + K1); + uasm_i_ctc1(&p, ZERO, 31); + uasm_l_fpu_1(&l, p); + } + + if (cpu_has_msa) { + /* + * If MSA is enabled, save MSACSR and clear it so that later + * instructions don't trigger MSAFPE for pending exceptions. + */ + uasm_i_mfc0(&p, T0, C0_CONFIG5); + uasm_i_ext(&p, T0, T0, 27, 1); /* MIPS_CONF5_MSAEN */ + uasm_il_beqz(&p, &r, T0, label_msa_1); + uasm_i_nop(&p); + uasm_i_cfcmsa(&p, T0, MSA_CSR); + uasm_i_sw(&p, T0, offsetof(struct kvm_vcpu_arch, fpu.msacsr), + K1); + uasm_i_ctcmsa(&p, MSA_CSR, ZERO); + uasm_l_msa_1(&l, p); + } + + /* Now that the new EBASE has been loaded, unset BEV and KSU_USER */ + uasm_i_addiu(&p, AT, ZERO, ~(ST0_EXL | KSU_USER | ST0_IE)); + uasm_i_and(&p, V0, V0, AT); + uasm_i_lui(&p, AT, ST0_CU0 >> 16); + uasm_i_or(&p, V0, V0, AT); + uasm_i_mtc0(&p, V0, C0_STATUS); + uasm_i_ehb(&p); + + /* Load up host GP */ + UASM_i_LW(&p, GP, offsetof(struct kvm_vcpu_arch, host_gp), K1); + + /* Need a stack before we can jump to "C" */ + UASM_i_LW(&p, SP, offsetof(struct kvm_vcpu_arch, host_stack), K1); + + /* Saved host state */ + UASM_i_ADDIU(&p, SP, SP, -(int)sizeof(struct pt_regs)); + + /* + * XXXKYMA do we need to load the host ASID, maybe not because the + * kernel entries are marked GLOBAL, need to verify + */ + + /* Restore host scratch registers, as we'll have clobbered them */ + kvm_mips_build_restore_scratch(&p, K0, SP); + + /* Restore RDHWR access */ + UASM_i_LA_mostly(&p, K0, (long)&hwrena); + uasm_i_lw(&p, K0, uasm_rel_lo((long)&hwrena), K0); + uasm_i_mtc0(&p, K0, C0_HWRENA); + + /* Jump to handler */ + /* + * XXXKYMA: not sure if this is safe, how large is the stack?? + * Now jump to the kvm_mips_handle_exit() to see if we can deal + * with this in the kernel + */ + UASM_i_LA(&p, T9, (unsigned long)kvm_mips_handle_exit); + uasm_i_jalr(&p, RA, T9); + UASM_i_ADDIU(&p, SP, SP, -CALLFRAME_SIZ); + + uasm_resolve_relocs(relocs, labels); + + p = kvm_mips_build_ret_from_exit(p); + + return p; +} + +/** + * kvm_mips_build_ret_from_exit() - Assemble guest exit return handler. + * @addr: Address to start writing code. + * + * Assemble the code to handle the return from kvm_mips_handle_exit(), either + * resuming the guest or returning to the host depending on the return value. + * + * Returns: Next address after end of written function. + */ +static void *kvm_mips_build_ret_from_exit(void *addr) +{ + u32 *p = addr; + struct uasm_label labels[2]; + struct uasm_reloc relocs[2]; + struct uasm_label *l = labels; + struct uasm_reloc *r = relocs; + + memset(labels, 0, sizeof(labels)); + memset(relocs, 0, sizeof(relocs)); + + /* Return from handler Make sure interrupts are disabled */ + uasm_i_di(&p, ZERO); + uasm_i_ehb(&p); + + /* + * XXXKYMA: k0/k1 could have been blown away if we processed + * an exception while we were handling the exception from the + * guest, reload k1 + */ + + uasm_i_move(&p, K1, S1); + UASM_i_ADDIU(&p, K1, K1, offsetof(struct kvm_vcpu, arch)); + + /* + * Check return value, should tell us if we are returning to the + * host (handle I/O etc)or resuming the guest + */ + uasm_i_andi(&p, T0, V0, RESUME_HOST); + uasm_il_bnez(&p, &r, T0, label_return_to_host); + uasm_i_nop(&p); + + p = kvm_mips_build_ret_to_guest(p); + + uasm_l_return_to_host(&l, p); + p = kvm_mips_build_ret_to_host(p); + + uasm_resolve_relocs(relocs, labels); + + return p; +} + +/** + * kvm_mips_build_ret_to_guest() - Assemble code to return to the guest. + * @addr: Address to start writing code. + * + * Assemble the code to handle return from the guest exit handler + * (kvm_mips_handle_exit()) back to the guest. + * + * Returns: Next address after end of written function. + */ +static void *kvm_mips_build_ret_to_guest(void *addr) +{ + u32 *p = addr; + + /* Put the saved pointer to vcpu (s1) back into the scratch register */ + UASM_i_MTC0(&p, S1, scratch_vcpu[0], scratch_vcpu[1]); + + /* Load up the Guest EBASE to minimize the window where BEV is set */ + UASM_i_LW(&p, T0, offsetof(struct kvm_vcpu_arch, guest_ebase), K1); + + /* Switch EBASE back to the one used by KVM */ + uasm_i_mfc0(&p, V1, C0_STATUS); + uasm_i_lui(&p, AT, ST0_BEV >> 16); + uasm_i_or(&p, K0, V1, AT); + uasm_i_mtc0(&p, K0, C0_STATUS); + uasm_i_ehb(&p); + build_set_exc_base(&p, T0); + + /* Setup status register for running guest in UM */ + uasm_i_ori(&p, V1, V1, ST0_EXL | KSU_USER | ST0_IE); + UASM_i_LA(&p, AT, ~(ST0_CU0 | ST0_MX)); + uasm_i_and(&p, V1, V1, AT); + uasm_i_mtc0(&p, V1, C0_STATUS); + uasm_i_ehb(&p); + + p = kvm_mips_build_enter_guest(p); + + return p; +} + +/** + * kvm_mips_build_ret_to_host() - Assemble code to return to the host. + * @addr: Address to start writing code. + * + * Assemble the code to handle return from the guest exit handler + * (kvm_mips_handle_exit()) back to the host, i.e. to the caller of the vcpu_run + * function generated by kvm_mips_build_vcpu_run(). + * + * Returns: Next address after end of written function. + */ +static void *kvm_mips_build_ret_to_host(void *addr) +{ + u32 *p = addr; + unsigned int i; + + /* EBASE is already pointing to Linux */ + UASM_i_LW(&p, K1, offsetof(struct kvm_vcpu_arch, host_stack), K1); + UASM_i_ADDIU(&p, K1, K1, -(int)sizeof(struct pt_regs)); + + /* + * r2/v0 is the return code, shift it down by 2 (arithmetic) + * to recover the err code + */ + uasm_i_sra(&p, K0, V0, 2); + uasm_i_move(&p, V0, K0); + + /* Load context saved on the host stack */ + for (i = 16; i < 31; ++i) { + if (i == 24) + i = 28; + UASM_i_LW(&p, i, offsetof(struct pt_regs, regs[i]), K1); + } + + /* Restore RDHWR access */ + UASM_i_LA_mostly(&p, K0, (long)&hwrena); + uasm_i_lw(&p, K0, uasm_rel_lo((long)&hwrena), K0); + uasm_i_mtc0(&p, K0, C0_HWRENA); + + /* Restore RA, which is the address we will return to */ + UASM_i_LW(&p, RA, offsetof(struct pt_regs, regs[RA]), K1); + uasm_i_jr(&p, RA); + uasm_i_nop(&p); + + return p; +} + |