[PATCH v8 13/38] KVM: arm64: Manage GCS registers for guests

Mark Brown
2024-02-03T12:31:09Z

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, as well as describe their fine grained traps to
nested virtualisation. Traps are already disabled.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 12 ++++++++++++
arch/arm64/kvm/emulate-nested.c | 4 ++++
arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 17 +++++++++++++++++
arch/arm64/kvm/sys_regs.c | 22 ++++++++++++++++++++++
4 files changed, 55 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 21c57b812569..6c7ea7f9cd92 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -388,6 +388,12 @@ enum vcpu_sysreg {
GCR_EL1, /* Tag Control Register */
TFSRE0_EL1, /* Tag Fault Status Register (EL0) */

+ /* 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 */
@@ -1221,6 +1227,12 @@ static inline bool __vcpu_has_feature(const struct kvm_arch *ka, int feature)

#define vcpu_has_feature(v, f) __vcpu_has_feature(&(v)->kvm->arch, (f))

+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/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index 431fd429932d..24eb7eccbae4 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -1098,8 +1098,12 @@ static const struct encoding_to_trap_config encoding_to_fgt[] __initconst = {
SR_FGT(SYS_ESR_EL1, HFGxTR, ESR_EL1, 1),
SR_FGT(SYS_DCZID_EL0, HFGxTR, DCZID_EL0, 1),
SR_FGT(SYS_CTR_EL0, HFGxTR, CTR_EL0, 1),
+ SR_FGT(SYS_GCSPR_EL0, HFGxTR, nGCS_EL0, 1),
SR_FGT(SYS_CSSELR_EL1, HFGxTR, CSSELR_EL1, 1),
SR_FGT(SYS_CPACR_EL1, HFGxTR, CPACR_EL1, 1),
+ SR_FGT(SYS_GCSCR_EL1, HFGxTR, nGCS_EL1, 1),
+ SR_FGT(SYS_GCSPR_EL1, HFGxTR, nGCS_EL1, 1),
+ SR_FGT(SYS_GCSCRE0_EL1, HFGxTR, nGCS_EL0, 1),
SR_FGT(SYS_CONTEXTIDR_EL1, HFGxTR, CONTEXTIDR_EL1, 1),
SR_FGT(SYS_CLIDR_EL1, HFGxTR, CLIDR_EL1, 1),
SR_FGT(SYS_CCSIDR_EL1, HFGxTR, CCSIDR_EL1, 1),
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 30253bd19917..83ba767e75d2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2000,6 +2000,23 @@ 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)
{
@@ -2376,6 +2393,10 @@ 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},

@@ -2462,6 +2483,7 @@ 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, .reset = reset_pmcr,

--
2.30.2