Re: [PATCH v7 1/3] arm64: kvm: Save/restore MTE registers
From: Steven Price
Date: Thu Feb 04 2021 - 09:35:56 EST
On 02/02/2021 15:36, Marc Zyngier wrote:
On 2021-01-15 15:28, Steven Price wrote:
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 | 4 ++
arch/arm64/include/asm/kvm_mte.h | 74 ++++++++++++++++++++++
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 | 4 ++
arch/arm64/kvm/sys_regs.c | 14 ++--
7 files changed, 104 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 11beda85ee7e..51590a397e4b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -148,6 +148,8 @@ enum vcpu_sysreg {
SCTLR_EL1, /* System Control Register */
ACTLR_EL1, /* Auxiliary Control Register */
CPACR_EL1, /* Coprocessor Access Control */
+ RGSR_EL1, /* Random Allocation Tag Seed Register */
+ GCR_EL1, /* Tag Control Register */
ZCR_EL1, /* SVE Control */
TTBR0_EL1, /* Translation Table Base Register 0 */
TTBR1_EL1, /* Translation Table Base Register 1 */
@@ -164,6 +166,8 @@ enum vcpu_sysreg {
TPIDR_EL1, /* Thread ID, Privileged */
AMAIR_EL1, /* Aux Memory Attribute Indirection Register */
CNTKCTL_EL1, /* Timer Control Register (EL1) */
+ TFSRE0_EL1, /* Tag Fault Status Register (EL0) */
+ TFSR_EL1, /* Tag Fault Stauts Register (EL1) */
s/Stauts/Status/
Is there any reason why the MTE registers aren't grouped together?
I has been under the impression this list is sorted by the encoding of
the system registers, although double checking I've screwed up the order
of TFSRE0_EL1/TFSR_EL1, and not all the other fields are sorted that way.
I'll move them together in their own section.
PAR_EL1, /* Physical Address Register */
MDSCR_EL1, /* Monitor Debug System Control Register */
MDCCINT_EL1, /* Monitor Debug Comms Channel Interrupt Enable
Reg */
diff --git a/arch/arm64/include/asm/kvm_mte.h
b/arch/arm64/include/asm/kvm_mte.h
new file mode 100644
index 000000000000..62bbfae77f33
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_mte.h
@@ -0,0 +1,74 @@
+/* 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]
+ mrs_s \reg1, SYS_TFSRE0_EL1
+ str \reg1, [\h_ctxt, #CPU_TFSRE0_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
+ ldr \reg1, [\g_ctxt, #CPU_TFSRE0_EL1]
+ msr_s SYS_TFSRE0_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]
+ mrs_s \reg1, SYS_TFSRE0_EL1
+ str \reg1, [\g_ctxt, #CPU_TFSRE0_EL1]
Can't the EL0 state save/restore be moved to the C code?
True, that should be safe. I'm not sure how I missed that.
+
+ 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
+ ldr \reg1, [\h_ctxt, #CPU_TFSRE0_EL1]
+ msr_s SYS_TFSRE0_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 8b5e7e5c3cc8..0a01975d331d 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -574,7 +574,8 @@
#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 f42fd9e33981..801531e1fa5c 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -105,6 +105,9 @@ 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..94d9736f0133 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -45,6 +45,8 @@ static inline void __sysreg_save_el1_state(struct
kvm_cpu_context *ctxt)
ctxt_sys_reg(ctxt, CNTKCTL_EL1) = read_sysreg_el1(SYS_CNTKCTL);
ctxt_sys_reg(ctxt, PAR_EL1) = read_sysreg_par();
ctxt_sys_reg(ctxt, TPIDR_EL1) = read_sysreg(tpidr_el1);
+ if (system_supports_mte())
+ ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
I already asked for it, and I'm going to ask for it again:
Most of the sysreg save/restore is guarded by a per-vcpu check
(HCR_EL2.ATA), while this one is unconditionally saved/restore
if the host is MTE capable. Why is that so?
Sorry, I thought your concern was for registers that affect the host (as
they are obviously more performance critical as they are hit on every
guest exit). Although I guess that's incorrect for nVHE which is what
all the cool kids want now ;)
The required infrastructure should be available, and if anything
is missing, let's add it.
I think I can see a way of accessing the necessary state.
ctxt_sys_reg(ctxt, SP_EL1) = read_sysreg(sp_el1);
ctxt_sys_reg(ctxt, ELR_EL1) = read_sysreg_el1(SYS_ELR);
@@ -106,6 +108,8 @@ static inline void
__sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
write_sysreg_el1(ctxt_sys_reg(ctxt, CNTKCTL_EL1), SYS_CNTKCTL);
write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1), par_el1);
write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1), tpidr_el1);
+ if (system_supports_mte())
+ write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
if (!has_vhe() &&
cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3313dedfa505..88d4f360949e 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1281,6 +1281,12 @@ 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;
+}
+
/* sys_reg_desc initialiser for known cpufeature ID registers */
#define ID_SANITISED(name) { \
SYS_DESC(SYS_##name), \
@@ -1449,8 +1455,8 @@ 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 },
+ { SYS_DESC(SYS_RGSR_EL1), undef_access, reset_unknown, RGSR_EL1,
.visibility = mte_visibility },
+ { SYS_DESC(SYS_GCR_EL1), undef_access, reset_unknown, GCR_EL1,
.visibility = mte_visibility },
Please don't mix implicit and designated assignments, as it is
pretty confusing.
Sorry - I was copying the style elsewhere in this list (e.g. just
below). I guess it might actually be better to create a new macro for
MTE similar to AMU / PTRAUTH - it should remove some of the boilerplate.
Thanks,
Steve
{ 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 },
@@ -1476,8 +1482,8 @@ 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 },
+ { SYS_DESC(SYS_TFSR_EL1), undef_access, reset_unknown, TFSR_EL1,
.visibility = mte_visibility },
+ { SYS_DESC(SYS_TFSRE0_EL1), undef_access, reset_unknown, TFSRE0_EL1,
.visibility = mte_visibility },
{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
Thanks,
M.