[PATCH v4 12/36] KVM: arm64: Manage GCS registers for guests

Mark Brown
2023-08-07T22:03:04Z

GCS introduces a number of system registers for EL1 and EL0, on systems
with GCS we need to context switch them and expose them to VMMs to allow
guests to use GCS. Traps are already disabled.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 12 ++++++++++++
arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 17 +++++++++++++++++
arch/arm64/kvm/sys_regs.c | 22 ++++++++++++++++++++++
3 files changed, 51 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index d3dd05bbfe23..a5bb00f58108 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -364,6 +364,12 @@ enum vcpu_sysreg {
PIR_EL1, /* Permission Indirection Register 1 (EL1) */
PIRE0_EL1, /* Permission Indirection Register 0 (EL1) */

+ /* Guarded Control Stack registers */
+ GCSCRE0_EL1, /* Guarded Control Stack Control (EL0) */
+ GCSCR_EL1, /* Guarded Control Stack Control (EL1) */
+ GCSPR_EL0, /* Guarded Control Stack Pointer (EL0) */
+ GCSPR_EL1, /* Guarded Control Stack Pointer (EL1) */
+
/* 32bit specific registers. */
DACR32_EL2, /* Domain Access Control Register */
IFSR32_EL2, /* Instruction Fault Status Register */
@@ -1136,6 +1142,12 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
#define kvm_vm_has_ran_once(kvm) \
(test_bit(KVM_ARCH_FLAG_HAS_RAN_ONCE, &(kvm)->arch.flags))

+static inline bool has_gcs(void)
+{
+ return IS_ENABLED(CONFIG_ARM64_GCS) &&
+ cpus_have_final_cap(ARM64_HAS_GCS);
+}
+
int kvm_trng_call(struct kvm_vcpu *vcpu);
#ifdef CONFIG_KVM
extern phys_addr_t hyp_mem_base;
diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
index bb6b571ec627..ec34d4a90717 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -25,6 +25,8 @@ static inline void __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
{
ctxt_sys_reg(ctxt, TPIDR_EL0) = read_sysreg(tpidr_el0);
ctxt_sys_reg(ctxt, TPIDRRO_EL0) = read_sysreg(tpidrro_el0);
+ if (has_gcs())
+ ctxt_sys_reg(ctxt, GCSPR_EL0) = read_sysreg_s(SYS_GCSPR_EL0);
}

static inline bool ctxt_has_mte(struct kvm_cpu_context *ctxt)
@@ -62,6 +64,12 @@ 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 (has_gcs()) {
+ ctxt_sys_reg(ctxt, GCSPR_EL1) = read_sysreg_el1(SYS_GCSPR);
+ ctxt_sys_reg(ctxt, GCSCR_EL1) = read_sysreg_el1(SYS_GCSCR);
+ ctxt_sys_reg(ctxt, GCSCRE0_EL1) = read_sysreg_s(SYS_GCSCRE0_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);
@@ -95,6 +103,8 @@ static inline void __sysreg_restore_user_state(struct kvm_cpu_context *ctxt)
{
write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL0), tpidr_el0);
write_sysreg(ctxt_sys_reg(ctxt, TPIDRRO_EL0), tpidrro_el0);
+ if (has_gcs())
+ write_sysreg_s(ctxt_sys_reg(ctxt, GCSPR_EL0), SYS_GCSPR_EL0);
}

static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
@@ -138,6 +148,13 @@ 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 (has_gcs()) {
+ write_sysreg_el1(ctxt_sys_reg(ctxt, GCSPR_EL1), SYS_GCSPR);
+ write_sysreg_el1(ctxt_sys_reg(ctxt, GCSCR_EL1), SYS_GCSCR);
+ write_sysreg_s(ctxt_sys_reg(ctxt, GCSCRE0_EL1),
+ SYS_GCSCRE0_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);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 2ca2973abe66..5b2f238d33be 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1768,6 +1768,23 @@ static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
.visibility = mte_visibility, \
}

+static unsigned int gcs_visibility(const struct kvm_vcpu *vcpu,
+ const struct sys_reg_desc *rd)
+{
+ if (has_gcs())
+ return 0;
+
+ return REG_HIDDEN;
+}
+
+#define GCS_REG(name) { \
+ SYS_DESC(SYS_##name), \
+ .access = undef_access, \
+ .reset = reset_unknown, \
+ .reg = name, \
+ .visibility = gcs_visibility, \
+}
+
static unsigned int el2_visibility(const struct kvm_vcpu *vcpu,
const struct sys_reg_desc *rd)
{
@@ -2080,6 +2097,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
PTRAUTH_KEY(APDB),
PTRAUTH_KEY(APGA),

+ GCS_REG(GCSCR_EL1),
+ GCS_REG(GCSPR_EL1),
+ GCS_REG(GCSCRE0_EL1),
+
{ SYS_DESC(SYS_SPSR_EL1), access_spsr},
{ SYS_DESC(SYS_ELR_EL1), access_elr},

@@ -2162,6 +2183,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
{ SYS_DESC(SYS_SMIDR_EL1), undef_access },
{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
{ SYS_DESC(SYS_CTR_EL0), access_ctr },
+ GCS_REG(GCSPR_EL0),
{ SYS_DESC(SYS_SVCR), undef_access },

{ PMU_SYS_REG(PMCR_EL0), .access = access_pmcr,

--
2.30.2