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KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV2/3 to protected VMs

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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>
Link: https://lore.kernel.org/r/20230404152321.413064-1-tabba@google.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Fuad Tabba 2023-04-04 16:23:21 +01:00 committed by Oliver Upton
parent f9ea835e99
commit e81625218b
3 changed files with 29 additions and 9 deletions
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26
arch/arm64/kvm/arm.c
View File

@ -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);

5
arch/arm64/kvm/hyp/include/nvhe/fixed_config.h
View File

@ -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) \
)
/*

7
arch/arm64/kvm/hyp/nvhe/sys_regs.c
View File

@ -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;
}