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[v4,23/36] KVM: arm64: Hide TCR2_EL1 from userspace when disabled for guests

Message ID 20241009190019.3222687-24-maz@kernel.org (mailing list archive)
State New
Headers show
Series KVM: arm64: Add EL2 support to FEAT_S1PIE/S1POE | expand

Commit Message

Marc Zyngier Oct. 9, 2024, 7 p.m. UTC 
From: Mark Brown <broonie@kernel.org>

When the guest does not support FEAT_TCR2 we should not allow any access
to it in order to ensure that we do not create spurious issues with guest
migration. Add a visibility operation for it.

Fixes: fbff56068232 ("KVM: arm64: Save/restore TCR2_EL1")
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240822-kvm-arm64-hide-pie-regs-v2-2-376624fa829c@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_host.h |  3 +++
 arch/arm64/kvm/sys_regs.c         | 29 ++++++++++++++++++++++++++---
 2 files changed, 29 insertions(+), 3 deletions(-)

Comments

Oliver Upton Oct. 10, 2024, 7:50 a.m. UTC | #1 
On Wed, Oct 09, 2024 at 08:00:06PM +0100, Marc Zyngier wrote:
> From: Mark Brown <broonie@kernel.org>
> 
> When the guest does not support FEAT_TCR2 we should not allow any access
> to it in order to ensure that we do not create spurious issues with guest
> migration. Add a visibility operation for it.

This should come at the beginning of ths series (same for the subsequent
S1PIE patch) so the EL2 registers use the correct visibility filtering
from the start.

> Fixes: fbff56068232 ("KVM: arm64: Save/restore TCR2_EL1")
> Signed-off-by: Mark Brown <broonie@kernel.org>
> Link: https://lore.kernel.org/r/20240822-kvm-arm64-hide-pie-regs-v2-2-376624fa829c@kernel.org
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/include/asm/kvm_host.h |  3 +++
>  arch/arm64/kvm/sys_regs.c         | 29 ++++++++++++++++++++++++++---
>  2 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1a5477181447c..197a7a08b3af5 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -1511,4 +1511,7 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
>  	(system_supports_fpmr() &&			\
>  	 kvm_has_feat((k), ID_AA64PFR2_EL1, FPMR, IMP))
>  
> +#define kvm_has_tcr2(k)				\
> +	(kvm_has_feat((k), ID_AA64MMFR3_EL1, TCRX, IMP))
> +

nit: we should consistently use this predicate if we want to keep it.
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1a5477181447c..197a7a08b3af5 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1511,4 +1511,7 @@  void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
 	(system_supports_fpmr() &&			\
 	 kvm_has_feat((k), ID_AA64PFR2_EL1, FPMR, IMP))
 
+#define kvm_has_tcr2(k)				\
+	(kvm_has_feat((k), ID_AA64MMFR3_EL1, TCRX, IMP))
+
 #endif /* __ARM64_KVM_HOST_H__ */
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 170a5bed68fe3..6226949b5bc79 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2348,6 +2348,27 @@  static unsigned int s1poe_visibility(const struct kvm_vcpu *vcpu,
 	return REG_HIDDEN;
 }
 
+static unsigned int tcr2_visibility(const struct kvm_vcpu *vcpu,
+				    const struct sys_reg_desc *rd)
+{
+	if (kvm_has_tcr2(vcpu->kvm))
+		return 0;
+
+	return REG_HIDDEN;
+}
+
+static unsigned int tcr2_el2_visibility(const struct kvm_vcpu *vcpu,
+				    const struct sys_reg_desc *rd)
+{
+	unsigned int r;
+
+	r = el2_visibility(vcpu, rd);
+	if (r)
+		return r;
+
+	return tcr2_visibility(vcpu, rd);
+}
+
 /*
  * Architected system registers.
  * Important: Must be sorted ascending by Op0, Op1, CRn, CRm, Op2
@@ -2532,7 +2553,8 @@  static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
 	{ SYS_DESC(SYS_TTBR1_EL1), access_vm_reg, reset_unknown, TTBR1_EL1 },
 	{ SYS_DESC(SYS_TCR_EL1), access_vm_reg, reset_val, TCR_EL1, 0 },
-	{ SYS_DESC(SYS_TCR2_EL1), access_vm_reg, reset_val, TCR2_EL1, 0 },
+	{ SYS_DESC(SYS_TCR2_EL1), access_vm_reg, reset_val, TCR2_EL1, 0,
+	  .visibility = tcr2_visibility },
 
 	PTRAUTH_KEY(APIA),
 	PTRAUTH_KEY(APIB),
@@ -2869,7 +2891,8 @@  static const struct sys_reg_desc sys_reg_descs[] = {
 	EL2_REG(TTBR0_EL2, access_rw, reset_val, 0),
 	EL2_REG(TTBR1_EL2, access_rw, reset_val, 0),
 	EL2_REG(TCR_EL2, access_rw, reset_val, TCR_EL2_RES1),
-	EL2_REG(TCR2_EL2, access_tcr2_el2, reset_val, TCR2_EL2_RES1),
+	EL2_REG_FILTERED(TCR2_EL2, access_tcr2_el2, reset_val, TCR2_EL2_RES1,
+			 tcr2_el2_visibility),
 	EL2_REG_VNCR(VTTBR_EL2, reset_val, 0),
 	EL2_REG_VNCR(VTCR_EL2, reset_val, 0),
 
@@ -4738,7 +4761,7 @@  void kvm_calculate_traps(struct kvm_vcpu *vcpu)
 		if (kvm_has_feat(kvm, ID_AA64ISAR2_EL1, MOPS, IMP))
 			vcpu->arch.hcrx_el2 |= (HCRX_EL2_MSCEn | HCRX_EL2_MCE2);
 
-		if (kvm_has_feat(kvm, ID_AA64MMFR3_EL1, TCRX, IMP))
+		if (kvm_has_tcr2(kvm))
 			vcpu->arch.hcrx_el2 |= HCRX_EL2_TCR2En;
 
 		if (kvm_has_fpmr(kvm))