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Merge branch kvm-arm64/idregs-6.12 into kvmarm/fixes
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* kvm-arm64/idregs-6.12:
  : .
  : Make some fields of ID_AA64DFR0_EL1 and ID_AA64PFR1_EL1
  : writable from userspace, so that a VMM can influence the
  : set of guest-visible features.
  :
  : - for ID_AA64DFR0_EL1: DoubleLock, WRPs, PMUVer and DebugVer
  :   are writable (courtesy of Shameer Kolothum)
  :
  : - for ID_AA64PFR1_EL1: BT, SSBS, CVS2_frac are writable
  :   (courtesy of Shaoqin Huang)
  : .
  KVM: selftests: aarch64: Add writable test for ID_AA64PFR1_EL1
  KVM: arm64: Allow userspace to change ID_AA64PFR1_EL1
  KVM: arm64: Use kvm_has_feat() to check if FEAT_SSBS is advertised to the guest
  KVM: arm64: Disable fields that KVM doesn't know how to handle in ID_AA64PFR1_EL1
  KVM: arm64: Make the exposed feature bits in AA64DFR0_EL1 writable from userspace

Signed-off-by: Marc Zyngier <maz@kernel.org>
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Marc Zyngier committed Oct 8, 2024
2 parents a1d402a + dc9b5d7 commit 9b7c3dd
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Showing 3 changed files with 55 additions and 11 deletions.
12 changes: 6 additions & 6 deletions arch/arm64/kvm/hypercalls.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -317,7 +317,7 @@ int kvm_smccc_call_handler(struct kvm_vcpu *vcpu)
* to the guest, and hide SSBS so that the
* guest stays protected.
*/
if (cpus_have_final_cap(ARM64_SSBS))
if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SSBS, IMP))
break;
fallthrough;
case SPECTRE_UNAFFECTED:
Expand Down Expand Up @@ -428,7 +428,7 @@ int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
* Convert the workaround level into an easy-to-compare number, where higher
* values mean better protection.
*/
static int get_kernel_wa_level(u64 regid)
static int get_kernel_wa_level(struct kvm_vcpu *vcpu, u64 regid)
{
switch (regid) {
case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
Expand All @@ -449,7 +449,7 @@ static int get_kernel_wa_level(u64 regid)
* don't have any FW mitigation if SSBS is there at
* all times.
*/
if (cpus_have_final_cap(ARM64_SSBS))
if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SSBS, IMP))
return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
fallthrough;
case SPECTRE_UNAFFECTED:
Expand Down Expand Up @@ -486,7 +486,7 @@ int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
val = get_kernel_wa_level(vcpu, reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
break;
case KVM_REG_ARM_STD_BMAP:
val = READ_ONCE(smccc_feat->std_bmap);
Expand Down Expand Up @@ -588,7 +588,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
return -EINVAL;

if (get_kernel_wa_level(reg->id) < val)
if (get_kernel_wa_level(vcpu, reg->id) < val)
return -EINVAL;

return 0;
Expand Down Expand Up @@ -624,7 +624,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
* We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
* other way around.
*/
if (get_kernel_wa_level(reg->id) < wa_level)
if (get_kernel_wa_level(vcpu, reg->id) < wa_level)
return -EINVAL;

return 0;
Expand Down
38 changes: 36 additions & 2 deletions arch/arm64/kvm/sys_regs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1527,6 +1527,14 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu,
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE);

val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_RNDR_trap);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE_frac);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_GCS);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_THE);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTEX);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_DF2);
val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_PFAR);
break;
case SYS_ID_AA64PFR2_EL1:
/* We only expose FPMR */
Expand Down Expand Up @@ -2376,7 +2384,19 @@ static const struct sys_reg_desc sys_reg_descs[] = {
ID_AA64PFR0_EL1_RAS |
ID_AA64PFR0_EL1_AdvSIMD |
ID_AA64PFR0_EL1_FP), },
ID_SANITISED(ID_AA64PFR1_EL1),
ID_WRITABLE(ID_AA64PFR1_EL1, ~(ID_AA64PFR1_EL1_PFAR |
ID_AA64PFR1_EL1_DF2 |
ID_AA64PFR1_EL1_MTEX |
ID_AA64PFR1_EL1_THE |
ID_AA64PFR1_EL1_GCS |
ID_AA64PFR1_EL1_MTE_frac |
ID_AA64PFR1_EL1_NMI |
ID_AA64PFR1_EL1_RNDR_trap |
ID_AA64PFR1_EL1_SME |
ID_AA64PFR1_EL1_RES0 |
ID_AA64PFR1_EL1_MPAM_frac |
ID_AA64PFR1_EL1_RAS_frac |
ID_AA64PFR1_EL1_MTE)),
ID_WRITABLE(ID_AA64PFR2_EL1, ID_AA64PFR2_EL1_FPMR),
ID_UNALLOCATED(4,3),
ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),
Expand All @@ -2390,7 +2410,21 @@ static const struct sys_reg_desc sys_reg_descs[] = {
.get_user = get_id_reg,
.set_user = set_id_aa64dfr0_el1,
.reset = read_sanitised_id_aa64dfr0_el1,
.val = ID_AA64DFR0_EL1_PMUVer_MASK |
/*
* Prior to FEAT_Debugv8.9, the architecture defines context-aware
* breakpoints (CTX_CMPs) as the highest numbered breakpoints (BRPs).
* KVM does not trap + emulate the breakpoint registers, and as such
* cannot support a layout that misaligns with the underlying hardware.
* While it may be possible to describe a subset that aligns with
* hardware, just prevent changes to BRPs and CTX_CMPs altogether for
* simplicity.
*
* See DDI0487K.a, section D2.8.3 Breakpoint types and linking
* of breakpoints for more details.
*/
.val = ID_AA64DFR0_EL1_DoubleLock_MASK |
ID_AA64DFR0_EL1_WRPs_MASK |
ID_AA64DFR0_EL1_PMUVer_MASK |
ID_AA64DFR0_EL1_DebugVer_MASK, },
ID_SANITISED(ID_AA64DFR1_EL1),
ID_UNALLOCATED(5,2),
Expand Down
16 changes: 13 additions & 3 deletions tools/testing/selftests/kvm/aarch64/set_id_regs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,8 @@ struct test_feature_reg {
}

static const struct reg_ftr_bits ftr_id_aa64dfr0_el1[] = {
S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, DoubleLock, 0),
REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, WRPs, 0),
S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, PMUVer, 0),
REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, DebugVer, ID_AA64DFR0_EL1_DebugVer_IMP),
REG_FTR_END,
Expand Down Expand Up @@ -134,6 +136,13 @@ static const struct reg_ftr_bits ftr_id_aa64pfr0_el1[] = {
REG_FTR_END,
};

static const struct reg_ftr_bits ftr_id_aa64pfr1_el1[] = {
REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64PFR1_EL1, CSV2_frac, 0),
REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64PFR1_EL1, SSBS, ID_AA64PFR1_EL1_SSBS_NI),
REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64PFR1_EL1, BT, 0),
REG_FTR_END,
};

static const struct reg_ftr_bits ftr_id_aa64mmfr0_el1[] = {
REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64MMFR0_EL1, ECV, 0),
REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64MMFR0_EL1, EXS, 0),
Expand Down Expand Up @@ -200,6 +209,7 @@ static struct test_feature_reg test_regs[] = {
TEST_REG(SYS_ID_AA64ISAR1_EL1, ftr_id_aa64isar1_el1),
TEST_REG(SYS_ID_AA64ISAR2_EL1, ftr_id_aa64isar2_el1),
TEST_REG(SYS_ID_AA64PFR0_EL1, ftr_id_aa64pfr0_el1),
TEST_REG(SYS_ID_AA64PFR1_EL1, ftr_id_aa64pfr1_el1),
TEST_REG(SYS_ID_AA64MMFR0_EL1, ftr_id_aa64mmfr0_el1),
TEST_REG(SYS_ID_AA64MMFR1_EL1, ftr_id_aa64mmfr1_el1),
TEST_REG(SYS_ID_AA64MMFR2_EL1, ftr_id_aa64mmfr2_el1),
Expand Down Expand Up @@ -569,9 +579,9 @@ int main(void)
test_cnt = ARRAY_SIZE(ftr_id_aa64dfr0_el1) + ARRAY_SIZE(ftr_id_dfr0_el1) +
ARRAY_SIZE(ftr_id_aa64isar0_el1) + ARRAY_SIZE(ftr_id_aa64isar1_el1) +
ARRAY_SIZE(ftr_id_aa64isar2_el1) + ARRAY_SIZE(ftr_id_aa64pfr0_el1) +
ARRAY_SIZE(ftr_id_aa64mmfr0_el1) + ARRAY_SIZE(ftr_id_aa64mmfr1_el1) +
ARRAY_SIZE(ftr_id_aa64mmfr2_el1) + ARRAY_SIZE(ftr_id_aa64zfr0_el1) -
ARRAY_SIZE(test_regs) + 2;
ARRAY_SIZE(ftr_id_aa64pfr1_el1) + ARRAY_SIZE(ftr_id_aa64mmfr0_el1) +
ARRAY_SIZE(ftr_id_aa64mmfr1_el1) + ARRAY_SIZE(ftr_id_aa64mmfr2_el1) +
ARRAY_SIZE(ftr_id_aa64zfr0_el1) - ARRAY_SIZE(test_regs) + 2;

ksft_set_plan(test_cnt);

Expand Down

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