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KVM: arm64: Save/restore SVE state for nVHE 

Implement the SVE save/restore for nVHE, following a similar
logic to that of the VHE implementation:

- the SVE state is switched on trap from EL1 to EL2

- no further changes to ZCR_EL2 occur as long as the guest isn't
  preempted or exit to userspace

- ZCR_EL2 is reset to its default value on the first SVE access from
  the host EL1, and ZCR_EL1 restored to the default guest value in
  vcpu_put()

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2021-03-11 18:29:55 +00:00
parent beed09067b
commit 8c8010d69c
3 changed files with 23 additions and 28 deletions
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10
arch/arm64/kvm/fpsimd.c
View File

@ -121,11 +121,17 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
local_irq_save(flags);
if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
if (guest_has_sve)
if (guest_has_sve) {
__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
/* Restore the VL that was saved when bound to the CPU */
if (!has_vhe())
sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
SYS_ZCR_EL1);
}
fpsimd_save_and_flush_cpu_state();
} else if (host_has_sve) {
} else if (has_vhe() && host_has_sve) {
/*
* The FPSIMD/SVE state in the CPU has not been touched, and we
* have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been

37
arch/arm64/kvm/hyp/include/hyp/switch.h
View File

@ -217,25 +217,19 @@ static inline void __hyp_sve_restore_guest(struct kvm_vcpu *vcpu)
/* Check for an FPSIMD/SVE trap and handle as appropriate */
static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
{
bool vhe, sve_guest, sve_host;
bool sve_guest, sve_host;
u8 esr_ec;
u64 reg;
if (!system_supports_fpsimd())
return false;
/*
* Currently system_supports_sve() currently implies has_vhe(),
* so the check is redundant. However, has_vhe() can be determined
* statically and helps the compiler remove dead code.
*/
if (has_vhe() && system_supports_sve()) {
if (system_supports_sve()) {
sve_guest = vcpu_has_sve(vcpu);
sve_host = vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE;
vhe = true;
} else {
sve_guest = false;
sve_host = false;
vhe = has_vhe();
}
esr_ec = kvm_vcpu_trap_get_class(vcpu);
@ -244,31 +238,26 @@ static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
return false;
/* Don't handle SVE traps for non-SVE vcpus here: */
if (!sve_guest)
if (esr_ec != ESR_ELx_EC_FP_ASIMD)
return false;
if (!sve_guest && esr_ec != ESR_ELx_EC_FP_ASIMD)
return false;
/* Valid trap. Switch the context: */
if (vhe) {
u64 reg = read_sysreg(cpacr_el1) | CPACR_EL1_FPEN;
if (has_vhe()) {
reg = CPACR_EL1_FPEN;
if (sve_guest)
reg |= CPACR_EL1_ZEN;
write_sysreg(reg, cpacr_el1);
sysreg_clear_set(cpacr_el1, 0, reg);
} else {
write_sysreg(read_sysreg(cptr_el2) & ~(u64)CPTR_EL2_TFP,
cptr_el2);
}
reg = CPTR_EL2_TFP;
if (sve_guest)
reg |= CPTR_EL2_TZ;
sysreg_clear_set(cptr_el2, reg, 0);
}
isb();
if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
/*
* In the SVE case, VHE is assumed: it is enforced by
* Kconfig and kvm_arch_init().
*/
if (sve_host)
__hyp_sve_save_host(vcpu);
else

4
arch/arm64/kvm/hyp/nvhe/switch.c
View File

@ -41,9 +41,9 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
__activate_traps_common(vcpu);
val = CPTR_EL2_DEFAULT;
val |= CPTR_EL2_TTA | CPTR_EL2_TZ | CPTR_EL2_TAM;
val |= CPTR_EL2_TTA | CPTR_EL2_TAM;
if (!update_fp_enabled(vcpu)) {
val |= CPTR_EL2_TFP;
val |= CPTR_EL2_TFP | CPTR_EL2_TZ;
__activate_traps_fpsimd32(vcpu);
}