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authorMark Brown <broonie@kernel.org>2022-04-19 12:22:34 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2022-04-22 18:51:23 +0100
commit861262ab862702061ae3355b811a07b15d1b2fc0 (patch)
tree82cadb0f309ac5e66aa767e2ee309087535c90ca /arch/arm64/kvm/fpsimd.c
parent51729fb1d0683df5e9e4d5dbe2ec46188f011da9 (diff)
downloadlinux-861262ab862702061ae3355b811a07b15d1b2fc0.tar.bz2
KVM: arm64: Handle SME host state when running guests
While we don't currently support SME in guests we do currently support it for the host system so we need to take care of SME's impact, including the floating point register state, when running guests. Simiarly to SVE we need to manage the traps in CPACR_RL1, what is new is the handling of streaming mode and ZA. Normally we defer any handling of the floating point register state until the guest first uses it however if the system is in streaming mode FPSIMD and SVE operations may generate SME traps which we would need to distinguish from actual attempts by the guest to use SME. Rather than do this for the time being if we are in streaming mode when entering the guest we force the floating point state to be saved immediately and exit streaming mode, meaning that the guest won't generate SME traps for supported operations. We could handle ZA in the access trap similarly to the FPSIMD/SVE state without the disruption caused by streaming mode but for simplicity handle it the same way as streaming mode for now. This will be revisited when we support SME for guests (hopefully before SME hardware becomes available), for now it will only incur additional cost on systems with SME and even there only if streaming mode or ZA are enabled. Signed-off-by: Mark Brown <broonie@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220419112247.711548-27-broonie@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kvm/fpsimd.c')
-rw-r--r--arch/arm64/kvm/fpsimd.c36
1 files changed, 36 insertions, 0 deletions
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 57d7ac3cfa0c..441edb9c398c 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -82,6 +82,26 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
+
+ /*
+ * We don't currently support SME guests but if we leave
+ * things in streaming mode then when the guest starts running
+ * FPSIMD or SVE code it may generate SME traps so as a
+ * special case if we are in streaming mode we force the host
+ * state to be saved now and exit streaming mode so that we
+ * don't have to handle any SME traps for valid guest
+ * operations. Do this for ZA as well for now for simplicity.
+ */
+ if (system_supports_sme()) {
+ if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
+ vcpu->arch.flags |= KVM_ARM64_HOST_SME_ENABLED;
+
+ if (read_sysreg_s(SYS_SVCR_EL0) &
+ (SYS_SVCR_EL0_SM_MASK | SYS_SVCR_EL0_ZA_MASK)) {
+ vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
+ fpsimd_save_and_flush_cpu_state();
+ }
+ }
}
/*
@@ -135,6 +155,22 @@ 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
+ * CPACR_EL1_DEFAULT and we need to reenable SME.
+ */
+ if (has_vhe() && system_supports_sme()) {
+ /* Also restore EL0 state seen on entry */
+ if (vcpu->arch.flags & KVM_ARM64_HOST_SME_ENABLED)
+ sysreg_clear_set(CPACR_EL1, 0,
+ CPACR_EL1_SMEN_EL0EN |
+ CPACR_EL1_SMEN_EL1EN);
+ else
+ sysreg_clear_set(CPACR_EL1,
+ CPACR_EL1_SMEN_EL0EN,
+ CPACR_EL1_SMEN_EL1EN);
+ }
+
if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
if (vcpu_has_sve(vcpu)) {
__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);