[PATCH v3 4/6] KVM: arm64: Introduce flag shadowing TIF_FOREIGN_FPSTATE

Marc Zyngier
2021-12-01T12:04:50Z

We currently have to maintain a mapping the thread_info structure
at EL2 in order to be able to check the TIF_FOREIGN_FPSTATE flag.

In order to eventually get rid of this, start with a vcpu flag that
shadows the thread flag on each entry into the hypervisor.

Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 2 ++
arch/arm64/kvm/arm.c | 1 +
arch/arm64/kvm/fpsimd.c | 8 ++++++++
arch/arm64/kvm/hyp/include/hyp/switch.h | 2 +-
4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3ccfc3e3e436..9f1703ebae15 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -441,6 +441,7 @@ struct kvm_vcpu_arch {

#define KVM_ARM64_DEBUG_STATE_SAVE_SPE (1 << 12) /* Save SPE context if active */
#define KVM_ARM64_DEBUG_STATE_SAVE_TRBE (1 << 13) /* Save TRBE context if active */
+#define KVM_ARM64_FP_FOREIGN_FPSTATE (1 << 14)

#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | \
KVM_GUESTDBG_USE_SW_BP | \
@@ -736,6 +737,7 @@ long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
/* Guest/host FPSIMD coordination helpers */
int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
+void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index e4727dc771bf..d1b93dc8d639 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -849,6 +849,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
}

kvm_arm_setup_debug(vcpu);
+ kvm_arch_vcpu_ctxflush_fp(vcpu);

/**************************************************************
* Enter the guest
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 2d15e1d6e214..a18b9c1744d5 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -79,6 +79,14 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
}

+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 the guest FPSIMD state was loaded, update the host's context
* tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index e65c2956b881..a243a2a82131 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -49,7 +49,7 @@ static inline bool update_fp_enabled(struct kvm_vcpu *vcpu)
* trap the accesses.
*/
if (!system_supports_fpsimd() ||
- vcpu->arch.host_thread_info->flags & _TIF_FOREIGN_FPSTATE)
+ vcpu->arch.flags & KVM_ARM64_FP_FOREIGN_FPSTATE)
vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
KVM_ARM64_FP_HOST);

--
2.30.2