[PATCH v14 24/39] KVM: arm64: Hide SME system registers from guests

Mark Brown
2022-04-19T11:25:37Z

For the time being we do not support use of SME by KVM guests, support for
this will be enabled in future. In order to prevent any side effects or
side channels via the new system registers, including the EL0 read/write
register TPIDR2, explicitly undefine all the system registers added by
SME and mask out the SME bitfield in SYS_ID_AA64PFR1.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/kvm/sys_regs.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 7b45c040cc27..689e53dd4cb1 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1132,6 +1132,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
case SYS_ID_AA64PFR1_EL1:
if (!kvm_has_mte(vcpu->kvm))
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_MTE);
+
+ val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_SME);
break;
case SYS_ID_AA64ISAR1_EL1:
if (!vcpu_has_ptrauth(vcpu))
@@ -1553,7 +1555,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
ID_UNALLOCATED(4,2),
ID_UNALLOCATED(4,3),
ID_SANITISED(ID_AA64ZFR0_EL1),
- ID_UNALLOCATED(4,5),
+ ID_HIDDEN(ID_AA64SMFR0_EL1),
ID_UNALLOCATED(4,6),
ID_UNALLOCATED(4,7),

@@ -1596,6 +1598,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {

{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
{ SYS_DESC(SYS_TRFCR_EL1), undef_access },
+ { SYS_DESC(SYS_SMPRI_EL1), undef_access },
+ { SYS_DESC(SYS_SMCR_EL1), undef_access },
{ 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 },
@@ -1678,8 +1682,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {

{ SYS_DESC(SYS_CCSIDR_EL1), access_ccsidr },
{ SYS_DESC(SYS_CLIDR_EL1), access_clidr },
+ { 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 },
+ { SYS_DESC(SYS_SVCR_EL0), undef_access },

{ PMU_SYS_REG(SYS_PMCR_EL0), .access = access_pmcr,
.reset = reset_pmcr, .reg = PMCR_EL0 },
@@ -1719,6 +1725,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {

{ SYS_DESC(SYS_TPIDR_EL0), NULL, reset_unknown, TPIDR_EL0 },
{ SYS_DESC(SYS_TPIDRRO_EL0), NULL, reset_unknown, TPIDRRO_EL0 },
+ { SYS_DESC(SYS_TPIDR2_EL0), undef_access },

{ SYS_DESC(SYS_SCXTNUM_EL0), undef_access },

--
2.30.2