Re: [PATCH v17 3/6] KVM: arm64: Save/restore MTE registers

[Fuad Tabba <tabba@google.com>]

Hi,

> diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
> new file mode 100644
> index 000000000000..88dd1199670b
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_mte.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2020-2021 ARM Ltd.
> + */
> +#ifndef __ASM_KVM_MTE_H
> +#define __ASM_KVM_MTE_H
> +
> +#ifdef __ASSEMBLY__
> +
> +#include <asm/sysreg.h>
> +
> +#ifdef CONFIG_ARM64_MTE
> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +       b       .L__skip_switch\@
> +alternative_else_nop_endif
> +       mrs     \reg1, hcr_el2
> +       tbz     \reg1, #(HCR_ATA_SHIFT), .L__skip_switch\@
> +
> +       mrs_s   \reg1, SYS_RGSR_EL1
> +       str     \reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +       mrs_s   \reg1, SYS_GCR_EL1
> +       str     \reg1, [\h_ctxt, #CPU_GCR_EL1]
> +
> +       ldr     \reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +       msr_s   SYS_RGSR_EL1, \reg1
> +       ldr     \reg1, [\g_ctxt, #CPU_GCR_EL1]
> +       msr_s   SYS_GCR_EL1, \reg1
> +
> +.L__skip_switch\@:
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +alternative_if_not ARM64_MTE
> +       b       .L__skip_switch\@
> +alternative_else_nop_endif
> +       mrs     \reg1, hcr_el2
> +       tbz     \reg1, #(HCR_ATA_SHIFT), .L__skip_switch\@
> +
> +       mrs_s   \reg1, SYS_RGSR_EL1
> +       str     \reg1, [\g_ctxt, #CPU_RGSR_EL1]
> +       mrs_s   \reg1, SYS_GCR_EL1
> +       str     \reg1, [\g_ctxt, #CPU_GCR_EL1]
> +
> +       ldr     \reg1, [\h_ctxt, #CPU_RGSR_EL1]
> +       msr_s   SYS_RGSR_EL1, \reg1
> +       ldr     \reg1, [\h_ctxt, #CPU_GCR_EL1]
> +       msr_s   SYS_GCR_EL1, \reg1
> +
> +       isb
> +
> +.L__skip_switch\@:
> +.endm
> +
> +#else /* CONFIG_ARM64_MTE */

nit: !CONFIG_ARM64_MTE (clearer and matches the style in kvm_ptrauth.h)

Cheers,
/fuad


> +
> +.macro mte_switch_to_guest g_ctxt, h_ctxt, reg1
> +.endm
> +
> +.macro mte_switch_to_hyp g_ctxt, h_ctxt, reg1
> +.endm
> +
> +#endif /* CONFIG_ARM64_MTE */
> +#endif /* __ASSEMBLY__ */
> +#endif /* __ASM_KVM_MTE_H */
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 65d15700a168..347ccac2341e 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -651,7 +651,8 @@
>
>  #define INIT_SCTLR_EL2_MMU_ON                                          \
>         (SCTLR_ELx_M  | SCTLR_ELx_C | SCTLR_ELx_SA | SCTLR_ELx_I |      \
> -        SCTLR_ELx_IESB | SCTLR_ELx_WXN | ENDIAN_SET_EL2 | SCTLR_EL2_RES1)
> +        SCTLR_ELx_IESB | SCTLR_ELx_WXN | ENDIAN_SET_EL2 |              \
> +        SCTLR_ELx_ITFSB | SCTLR_EL2_RES1)
>
>  #define INIT_SCTLR_EL2_MMU_OFF \
>         (SCTLR_EL2_RES1 | ENDIAN_SET_EL2)
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 0cb34ccb6e73..6f0044cb233e 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -111,6 +111,8 @@ int main(void)
>    DEFINE(VCPU_WORKAROUND_FLAGS,        offsetof(struct kvm_vcpu, arch.workaround_flags));
>    DEFINE(VCPU_HCR_EL2,         offsetof(struct kvm_vcpu, arch.hcr_el2));
>    DEFINE(CPU_USER_PT_REGS,     offsetof(struct kvm_cpu_context, regs));
> +  DEFINE(CPU_RGSR_EL1,         offsetof(struct kvm_cpu_context, sys_regs[RGSR_EL1]));
> +  DEFINE(CPU_GCR_EL1,          offsetof(struct kvm_cpu_context, sys_regs[GCR_EL1]));
>    DEFINE(CPU_APIAKEYLO_EL1,    offsetof(struct kvm_cpu_context, sys_regs[APIAKEYLO_EL1]));
>    DEFINE(CPU_APIBKEYLO_EL1,    offsetof(struct kvm_cpu_context, sys_regs[APIBKEYLO_EL1]));
>    DEFINE(CPU_APDAKEYLO_EL1,    offsetof(struct kvm_cpu_context, sys_regs[APDAKEYLO_EL1]));
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index e831d3dfd50d..435346ea1504 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -13,6 +13,7 @@
>  #include <asm/kvm_arm.h>
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_mmu.h>
> +#include <asm/kvm_mte.h>
>  #include <asm/kvm_ptrauth.h>
>
>         .text
> @@ -51,6 +52,9 @@ alternative_else_nop_endif
>
>         add     x29, x0, #VCPU_CONTEXT
>
> +       // mte_switch_to_guest(g_ctxt, h_ctxt, tmp1)
> +       mte_switch_to_guest x29, x1, x2
> +
>         // Macro ptrauth_switch_to_guest format:
>         //      ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3)
>         // The below macro to restore guest keys is not implemented in C code
> @@ -142,6 +146,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
>         // when this feature is enabled for kernel code.
>         ptrauth_switch_to_hyp x1, x2, x3, x4, x5
>
> +       // mte_switch_to_hyp(g_ctxt, h_ctxt, reg1)
> +       mte_switch_to_hyp x1, x2, x3
> +
>         // Restore hyp's sp_el0
>         restore_sp_el0 x2, x3
>
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index cce43bfe158f..de7e14c862e6 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> @@ -14,6 +14,7 @@
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_emulate.h>
>  #include <asm/kvm_hyp.h>
> +#include <asm/kvm_mmu.h>
>
>  static inline void __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
>  {
> @@ -26,6 +27,16 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
>         ctxt_sys_reg(ctxt, TPIDRRO_EL0) = read_sysreg(tpidrro_el0);
>  }
>
> +static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
> +{
> +       struct kvm_vcpu *vcpu = ctxt->__hyp_running_vcpu;
> +
> +       if (!vcpu)
> +               vcpu = container_of(ctxt, struct kvm_vcpu, arch.ctxt);
> +
> +       return kvm_has_mte(kern_hyp_va(vcpu->kvm));
> +}
> +
>  static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  {
>         ctxt_sys_reg(ctxt, CSSELR_EL1)  = read_sysreg(csselr_el1);
> @@ -46,6 +57,11 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>         ctxt_sys_reg(ctxt, PAR_EL1)     = read_sysreg_par();
>         ctxt_sys_reg(ctxt, TPIDR_EL1)   = read_sysreg(tpidr_el1);
>
> +       if (ctxt_has_mte(ctxt)) {
> +               ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
> +               ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
> +       }
> +
>         ctxt_sys_reg(ctxt, SP_EL1)      = read_sysreg(sp_el1);
>         ctxt_sys_reg(ctxt, ELR_EL1)     = read_sysreg_el1(SYS_ELR);
>         ctxt_sys_reg(ctxt, SPSR_EL1)    = read_sysreg_el1(SYS_SPSR);
> @@ -107,6 +123,11 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>         write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1),       par_el1);
>         write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1),     tpidr_el1);
>
> +       if (ctxt_has_mte(ctxt)) {
> +               write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
> +               write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
> +       }
> +
>         if (!has_vhe() &&
>             cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
>             ctxt->__hyp_running_vcpu) {
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 36f67f8deae1..5c75b24eae21 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1309,6 +1309,20 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>         return true;
>  }
>
> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
> +                                  const struct sys_reg_desc *rd)
> +{
> +       return REG_HIDDEN;
> +}
> +
> +#define MTE_REG(name) {                                \
> +       SYS_DESC(SYS_##name),                   \
> +       .access = undef_access,                 \
> +       .reset = reset_unknown,                 \
> +       .reg = name,                            \
> +       .visibility = mte_visibility,           \
> +}
> +
>  /* sys_reg_desc initialiser for known cpufeature ID registers */
>  #define ID_SANITISED(name) {                   \
>         SYS_DESC(SYS_##name),                   \
> @@ -1477,8 +1491,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>         { SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
>         { SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>
> -       { SYS_DESC(SYS_RGSR_EL1), undef_access },
> -       { SYS_DESC(SYS_GCR_EL1), undef_access },
> +       MTE_REG(RGSR_EL1),
> +       MTE_REG(GCR_EL1),
>
>         { SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>         { SYS_DESC(SYS_TRFCR_EL1), undef_access },
> @@ -1505,8 +1519,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>         { SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
>         { SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>
> -       { SYS_DESC(SYS_TFSR_EL1), undef_access },
> -       { SYS_DESC(SYS_TFSRE0_EL1), undef_access },
> +       MTE_REG(TFSR_EL1),
> +       MTE_REG(TFSRE0_EL1),
>
>         { SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
>         { SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
> --
> 2.20.1
>
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