@@ -615,7 +615,6 @@ struct cpu_sve_state {
struct kvm_host_data {
#define KVM_HOST_DATA_FLAG_HAS_SPE 0
#define KVM_HOST_DATA_FLAG_HAS_TRBE 1
-#define KVM_HOST_DATA_FLAG_HOST_SME_ENABLED 3
#define KVM_HOST_DATA_FLAG_TRBE_ENABLED 4
#define KVM_HOST_DATA_FLAG_EL1_TRACING_CONFIGURED 5
unsigned long flags;
@@ -65,12 +65,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
fpsimd_save_and_flush_cpu_state();
*host_data_ptr(fp_owner) = FP_STATE_FREE;
- if (system_supports_sme()) {
- host_data_clear_flag(HOST_SME_ENABLED);
- if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
- host_data_set_flag(HOST_SME_ENABLED);
- }
-
/*
* If normal guests gain SME support, maintain this behavior for pKVM
* guests, which don't support SME.
@@ -141,21 +135,6 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
local_irq_save(flags);
- /*
- * If we have VHE then the Hyp code will reset CPACR_EL1 to
- * the default value and we need to reenable SME.
- */
- if (has_vhe() && system_supports_sme()) {
- /* Also restore EL0 state seen on entry */
- if (host_data_test_flag(HOST_SME_ENABLED))
- sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_SMEN);
- else
- sysreg_clear_set(CPACR_EL1,
- CPACR_EL1_SMEN_EL0EN,
- CPACR_EL1_SMEN_EL1EN);
- isb();
- }
-
if (guest_owns_fp_regs()) {
if (vcpu_has_sve(vcpu)) {
u64 zcr = read_sysreg_el1(SYS_ZCR);
When KVM is in VHE mode, the host kernel tries to save and restore the configuration of CPACR_EL1.SMEN (i.e. CPTR_EL2.SMEN when HCR_EL2.E2H=1) across kvm_arch_vcpu_load_fp() and kvm_arch_vcpu_put_fp(), since the configuration may be clobbered by hyp when running a vCPU. This logic has historically been broken, and is currently redundant. This logic was originally introduced in commit: 861262ab86270206 ("KVM: arm64: Handle SME host state when running guests") At the time, the VHE hyp code would reset CPTR_EL2.SMEN to 0b00 when returning to the host, trapping host access to SME state. Unfortunately, this was unsafe as the host could take a softirq before calling kvm_arch_vcpu_put_fp(), and if a softirq handler were to use kernel mode NEON the resulting attempt to save the live FPSIMD/SVE/SME state would result in a fatal trap. That issue was limited to VHE mode. For nVHE/hVHE modes, KVM always saved/restored the host kernel's CPACR_EL1 value, and configured CPTR_EL2.TSM to 0b0, ensuring that host usage of SME would not be trapped. The issue above was incidentally fixed by commit: 375110ab51dec5dc ("KVM: arm64: Fix resetting SME trap values on reset for (h)VHE") That commit changed the VHE hyp code to configure CPTR_EL2.SMEN to 0b01 when returning to the host, permitting host kernel usage of SME, avoiding the issue described above. At the time, this was not identified as a fix for commit 861262ab86270206. Now that the host eagerly saves and unbinds its own FPSIMD/SVE/SME state, there's no need to save/restore the state of the EL0 SME trap. The kernel can safely save/restore state without trapping, as described above, and will restore userspace state (including trap controls) before returning to userspace. Remove the redundant logic. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Mark Brown <broonie@kernel.org> Tested-by: Mark Brown <broonie@kernel.org> Acked-by: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Fuad Tabba <tabba@google.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Oliver Upton <oliver.upton@linux.dev> --- arch/arm64/include/asm/kvm_host.h | 1 - arch/arm64/kvm/fpsimd.c | 21 --------------------- 2 files changed, 22 deletions(-)