diff options
| author | Marc Zyngier <maz@kernel.org> | 2022-05-28 12:38:13 +0100 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2022-06-09 12:01:51 +0100 |
| commit | e9ada6c208c15c907afe5afb1aa82e23e81eb8ba (patch) | |
| tree | e2f62c62cd25be94baf99f4cc23e5752bd9c0344 /arch/arm64/kvm/fpsimd.c | |
| parent | 039f49c4cafb785504c678f28664d088e0108d35 (diff) | |
KVM: arm64: Drop FP_FOREIGN_STATE from the hypervisor code
The vcpu KVM_ARM64_FP_FOREIGN_FPSTATE flag tracks the thread's own
TIF_FOREIGN_FPSTATE so that we can evaluate just before running
the vcpu whether it the FP regs contain something that is owned
by the vcpu or not by updating the rest of the FP flags.
We do this in the hypervisor code in order to make sure we're
in a context where we are not interruptible. But we already
have a hook in the run loop to generate this flag. We may as
well update the FP flags directly and save the pointless flag
tracking.
Whilst we're at it, rename update_fp_enabled() to guest_owns_fp_regs()
to indicate what the leftover of this helper actually do.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'arch/arm64/kvm/fpsimd.c')
| -rw-r--r-- | arch/arm64/kvm/fpsimd.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 6012b08ecb14..edbc0183c89b 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -107,16 +107,19 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) } /* - * Called just before entering the guest once we are no longer - * preemptable. Syncs the host's TIF_FOREIGN_FPSTATE with the KVM - * mirror of the flag used by the hypervisor. + * Called just before entering the guest once we are no longer preemptable + * and interrupts are disabled. If we have managed to run anything using + * FP while we were preemptible (such as off the back of an interrupt), + * then neither the host nor the guest own the FP hardware (and it was the + * responsibility of the code that used FP to save the existing state). + * + * Note that not supporting FP is basically the same thing as far as the + * hypervisor is concerned (nothing to save). */ void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu) { - if (test_thread_flag(TIF_FOREIGN_FPSTATE)) - vcpu->arch.flags |= KVM_ARM64_FP_FOREIGN_FPSTATE; - else - vcpu->arch.flags &= ~KVM_ARM64_FP_FOREIGN_FPSTATE; + if (!system_supports_fpsimd() || test_thread_flag(TIF_FOREIGN_FPSTATE)) + vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED | KVM_ARM64_FP_HOST); } /* |