* [PATCH v5] KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV2/3 to protected VMs
@ 2023-04-04 15:23 Fuad Tabba
2023-04-04 15:55 ` Oliver Upton
0 siblings, 1 reply; 2+ messages in thread
From: Fuad Tabba @ 2023-04-04 15:23 UTC (permalink / raw)
To: kvmarm
Cc: maz, oliver.upton, oupton, will, pbonzini, james.morse,
alexandru.elisei, suzuki.poulose, reijiw, ricarkol, rananta,
jingzhangos, tabba
The existing pKVM code attempts to advertise CSV2/3 using values
initialized to 0, but never set. To advertise CSV2/3 to protected
guests, pass the CSV2/3 values to hyp when initializing hyp's
view of guests' ID_AA64PFR0_EL1.
Similar to non-protected KVM, these are system-wide, rather than
per cpu, for simplicity.
Fixes: 6c30bfb18d0b ("KVM: arm64: Add handlers for protected VM System Registers")
Signed-off-by: Fuad Tabba <tabba@google.com>
---
Based on: 197b6b60ae7b (6.3-rc4)
Changes from V4: Advertisement of CSV2/3 should be based on what
KVM advertises to all VMs, and not only on the underlying
hardware's ID_AA64PFR0_EL1 (Marc).
arch/arm64/kvm/arm.c | 26 ++++++++++++++++++-
.../arm64/kvm/hyp/include/nvhe/fixed_config.h | 5 +++-
arch/arm64/kvm/hyp/nvhe/sys_regs.c | 7 -----
3 files changed, 29 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 3bd732eaf087..e850aeccebb9 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1889,9 +1889,33 @@ static int __init do_pkvm_init(u32 hyp_va_bits)
return ret;
}
+static u64 get_hyp_id_aa64pfr0_el1(void)
+{
+ /*
+ * Track whether the system isn't affected by spectre/meltdown in the
+ * hypervisor's view of id_aa64pfr0_el1, used for protected VMs.
+ * Although this is per-CPU, we make it global for simplicity, e.g., not
+ * to have to worry about vcpu migration.
+ *
+ * Unlike for non-protected VMs, userspace cannot override this for
+ * protected VMs.
+ */
+ u64 val = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+
+ val &= ~(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2) |
+ ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3));
+
+ val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2),
+ arm64_get_spectre_v2_state() == SPECTRE_UNAFFECTED);
+ val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3),
+ arm64_get_meltdown_state() == SPECTRE_UNAFFECTED);
+
+ return val;
+}
+
static void kvm_hyp_init_symbols(void)
{
- kvm_nvhe_sym(id_aa64pfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+ kvm_nvhe_sym(id_aa64pfr0_el1_sys_val) = get_hyp_id_aa64pfr0_el1();
kvm_nvhe_sym(id_aa64pfr1_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1);
kvm_nvhe_sym(id_aa64isar0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64ISAR0_EL1);
kvm_nvhe_sym(id_aa64isar1_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64ISAR1_EL1);
diff --git a/arch/arm64/kvm/hyp/include/nvhe/fixed_config.h b/arch/arm64/kvm/hyp/include/nvhe/fixed_config.h
index 07edfc7524c9..37440e1dda93 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/fixed_config.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/fixed_config.h
@@ -33,11 +33,14 @@
* Allow for protected VMs:
* - Floating-point and Advanced SIMD
* - Data Independent Timing
+ * - Spectre/Meltdown Mitigation
*/
#define PVM_ID_AA64PFR0_ALLOW (\
ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_FP) | \
ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_AdvSIMD) | \
- ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_DIT) \
+ ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_DIT) | \
+ ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2) | \
+ ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3) \
)
/*
diff --git a/arch/arm64/kvm/hyp/nvhe/sys_regs.c b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
index 08d2b004f4b7..edd969a1f36b 100644
--- a/arch/arm64/kvm/hyp/nvhe/sys_regs.c
+++ b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
@@ -85,19 +85,12 @@ static u64 get_restricted_features_unsigned(u64 sys_reg_val,
static u64 get_pvm_id_aa64pfr0(const struct kvm_vcpu *vcpu)
{
- const struct kvm *kvm = (const struct kvm *)kern_hyp_va(vcpu->kvm);
u64 set_mask = 0;
u64 allow_mask = PVM_ID_AA64PFR0_ALLOW;
set_mask |= get_restricted_features_unsigned(id_aa64pfr0_el1_sys_val,
PVM_ID_AA64PFR0_RESTRICT_UNSIGNED);
- /* Spectre and Meltdown mitigation in KVM */
- set_mask |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2),
- (u64)kvm->arch.pfr0_csv2);
- set_mask |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3),
- (u64)kvm->arch.pfr0_csv3);
-
return (id_aa64pfr0_el1_sys_val & allow_mask) | set_mask;
}
base-commit: 197b6b60ae7bc51dd0814953c562833143b292aa
--
2.40.0.348.gf938b09366-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v5] KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV2/3 to protected VMs
2023-04-04 15:23 [PATCH v5] KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV2/3 to protected VMs Fuad Tabba
@ 2023-04-04 15:55 ` Oliver Upton
0 siblings, 0 replies; 2+ messages in thread
From: Oliver Upton @ 2023-04-04 15:55 UTC (permalink / raw)
To: Fuad Tabba, kvmarm
Cc: Oliver Upton, maz, reijiw, pbonzini, will, james.morse,
alexandru.elisei, jingzhangos, ricarkol, rananta, suzuki.poulose
On Tue, 4 Apr 2023 16:23:21 +0100, Fuad Tabba wrote:
> The existing pKVM code attempts to advertise CSV2/3 using values
> initialized to 0, but never set. To advertise CSV2/3 to protected
> guests, pass the CSV2/3 values to hyp when initializing hyp's
> view of guests' ID_AA64PFR0_EL1.
>
> Similar to non-protected KVM, these are system-wide, rather than
> per cpu, for simplicity.
>
> [...]
Applied to kvmarm/fixes, thanks!
[1/1] KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV2/3 to protected VMs
https://git.kernel.org/kvmarm/kvmarm/c/e81625218bf7
--
Best,
Oliver
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-04-04 15:23 [PATCH v5] KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV2/3 to protected VMs Fuad Tabba
2023-04-04 15:55 ` Oliver Upton
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