[PATCH v11 3/6] arm64: kvm: Save/restore MTE registers

From: Steven Price
Date: Fri Apr 16 2021 - 11:43:36 EST

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Define the new system registers that MTE introduces and context switch
them. The MTE feature is still hidden from the ID register as it isn't
supported in a VM yet.

Signed-off-by: Steven Price <steven.price@xxxxxxx>
---
arch/arm64/include/asm/kvm_host.h | 6 ++
arch/arm64/include/asm/kvm_mte.h | 66 ++++++++++++++++++++++
arch/arm64/include/asm/sysreg.h | 3 +-
arch/arm64/kernel/asm-offsets.c | 3 +
arch/arm64/kvm/hyp/entry.S | 7 +++
arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 21 +++++++
arch/arm64/kvm/sys_regs.c | 22 ++++++--
7 files changed, 123 insertions(+), 5 deletions(-)
create mode 100644 arch/arm64/include/asm/kvm_mte.h

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1170ee137096..d00cc3590f6e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -208,6 +208,12 @@ enum vcpu_sysreg {
CNTP_CVAL_EL0,
CNTP_CTL_EL0,

+ /* Memory Tagging Extension registers */
+ RGSR_EL1, /* Random Allocation Tag Seed Register */
+ GCR_EL1, /* Tag Control Register */
+ TFSR_EL1, /* Tag Fault Status Register (EL1) */
+ TFSRE0_EL1, /* Tag Fault Status Register (EL0) */
+
/* 32bit specific registers. Keep them at the end of the range */
DACR32_EL2, /* Domain Access Control Register */
IFSR32_EL2, /* Instruction Fault Status Register */
diff --git a/arch/arm64/include/asm/kvm_mte.h b/arch/arm64/include/asm/kvm_mte.h
new file mode 100644
index 000000000000..6541c7d6ce06
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_mte.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 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
+ and \reg1, \reg1, #(HCR_ATA)
+ cbz \reg1, .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
+ and \reg1, \reg1, #(HCR_ATA)
+ cbz \reg1, .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
+
+.L__skip_switch\@:
+.endm
+
+#else /* CONFIG_ARM64_MTE */
+
+.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 dfd4edbfe360..5424d195cf96 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -580,7 +580,8 @@
#define SCTLR_ELx_M (BIT(0))

#define SCTLR_ELx_FLAGS (SCTLR_ELx_M | SCTLR_ELx_A | SCTLR_ELx_C | \
- SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
+ SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
+ SCTLR_ELx_ITFSB)

/* SCTLR_EL2 specific flags. */
#define SCTLR_EL2_RES1 ((BIT(4)) | (BIT(5)) | (BIT(11)) | (BIT(16)) | \
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index a36e2fc330d4..944e4f1f45d9 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -108,6 +108,9 @@ 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_TFSRE0_EL1, offsetof(struct kvm_cpu_context, sys_regs[TFSRE0_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 b0afad7a99c6..c67582c6dd55 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
@@ -140,6 +144,9 @@ 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 18c87500a7a8..377ae6efb0ef 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1303,6 +1303,20 @@ 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), \
@@ -1471,8 +1485,8 @@ 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_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
@@ -1498,8 +1512,8 @@ 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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