Commit e8162521 authored by Fuad Tabba's avatar Fuad Tabba Committed by Oliver Upton
Browse files

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



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: 6c30bfb1 ("KVM: arm64: Add handlers for protected VM System Registers")
Signed-off-by: default avatarFuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20230404152321.413064-1-tabba@google.com


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent f9ea835e

arch/arm64/kvm/arm.c

+25 −1
Original line number Diff line number Diff line
@@ -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);

arch/arm64/kvm/hyp/include/nvhe/fixed_config.h

+4 −1
Original line number Diff line number Diff line
@@ -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) \

	)



/*

arch/arm64/kvm/hyp/nvhe/sys_regs.c

+0 −7
Original line number Diff line number Diff line
@@ -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;

}