[1/7] KVM: arm64: Move SVCR into the sysreg array

Commit Message

Marc Zyngier July 8, 2024, 3:44 p.m. UTC

SVCR is just a system register, and has no purpose being outside
of the sysreg array. If anything, it only makes it more difficult
to eventually support SME one day. If ever.

Move it into the array with its little friends, and associate it
with a visibility predicate.

Although this is dead code, it at least paves the way for the
next set of FP-related extensions.

Signed-off-by: Marc Zyngier <[e-mail]>
---
 arch/arm64/include/asm/kvm_host.h |  4 +++-
 arch/arm64/kvm/fpsimd.c           |  2 +-
 arch/arm64/kvm/sys_regs.c         | 11 ++++++++++-
 3 files changed, 14 insertions(+), 3 deletions(-)

Comments

Mark Brown July 8, 2024, 3:53 p.m. UTC | #1

On Mon, Jul 08, 2024 at 04:44:32PM +0100, Marc Zyngier wrote:
> SVCR is just a system register, and has no purpose being outside
> of the sysreg array. If anything, it only makes it more difficult
> to eventually support SME one day. If ever.

Right, that's why the SME serie has a patch adding it to sysreg -
it was kept out due to feature detection.

Patch

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 25a3b72fbacf2..0b3d7697ca0a7 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -446,6 +446,9 @@  enum vcpu_sysreg {
 	GCR_EL1,	/* Tag Control Register */
 	TFSRE0_EL1,	/* Tag Fault Status Register (EL0) */
 
+	/* FP/SIMD/SVE */
+	SVCR,
+
 	/* 32bit specific registers. */
 	DACR32_EL2,	/* Domain Access Control Register */
 	IFSR32_EL2,	/* Instruction Fault Status Register */
@@ -664,7 +667,6 @@  struct kvm_vcpu_arch {
 	void *sve_state;
 	enum fp_type fp_type;
 	unsigned int sve_max_vl;
-	u64 svcr;
 	u64 fpmr;
 
 	/* Stage 2 paging state used by the hardware on next switch */
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index c53e5b14038dc..e6425414d301f 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -134,7 +134,7 @@  void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
 		fp_state.sve_state = vcpu->arch.sve_state;
 		fp_state.sve_vl = vcpu->arch.sve_max_vl;
 		fp_state.sme_state = NULL;
-		fp_state.svcr = &vcpu->arch.svcr;
+		fp_state.svcr = &__vcpu_sys_reg(vcpu, SVCR);
 		fp_state.fpmr = &vcpu->arch.fpmr;
 		fp_state.fp_type = &vcpu->arch.fp_type;
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index c90324060436b..2dc6cab43b2f8 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1669,6 +1669,15 @@  static unsigned int sve_visibility(const struct kvm_vcpu *vcpu,
 	return REG_HIDDEN;
 }
 
+static unsigned int sme_visibility(const struct kvm_vcpu *vcpu,
+				   const struct sys_reg_desc *rd)
+{
+	if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SME, IMP))
+		return 0;
+
+	return REG_HIDDEN;
+}
+
 static u64 read_sanitised_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 					  const struct sys_reg_desc *rd)
 {
@@ -2535,7 +2544,7 @@  static const struct sys_reg_desc sys_reg_descs[] = {
 			     CTR_EL0_IDC_MASK |
 			     CTR_EL0_DminLine_MASK |
 			     CTR_EL0_IminLine_MASK),
-	{ SYS_DESC(SYS_SVCR), undef_access },
+	{ SYS_DESC(SYS_SVCR), undef_access, reset_val, SVCR, 0, .visibility = sme_visibility  },
 
 	{ PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr,
 	  .reg = PMCR_EL0, .get_user = get_pmcr, .set_user = set_pmcr },