[PATCH v6 1/5] KVM: arm64: Share all userspace hardened thread data with the hypervisor

Mark Brown
2024-03-29T00:13:58Z

As part of the lazy FPSIMD state transitioning done by the hypervisor we
currently share the userpsace FPSIMD state in thread->uw.fpsimd_state with
the host. Since this struct is non-extensible userspace ABI we have to keep
the definition as is but the addition of FPMR in the 2023 dpISA means that
we will want to share more storage with the host. To facilitate this
refactor the current code to share the entire thread->uw rather than just
the one field.

The large number of references to fpsimd_state make it very inconvenient
to add an additional wrapper struct.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 3 ++-
arch/arm64/include/asm/processor.h | 2 +-
arch/arm64/kvm/fpsimd.c | 13 ++++++-------
arch/arm64/kvm/hyp/include/hyp/switch.h | 2 +-
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 4 ++--
5 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 9e8a496fb284..8a251f0da900 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -27,6 +27,7 @@
#include <asm/fpsimd.h>
#include <asm/kvm.h>
#include <asm/kvm_asm.h>
+#include <asm/processor.h>
#include <asm/vncr_mapping.h>

#define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -640,7 +641,7 @@ struct kvm_vcpu_arch {
struct kvm_guest_debug_arch vcpu_debug_state;
struct kvm_guest_debug_arch external_debug_state;

- struct user_fpsimd_state *host_fpsimd_state; /* hyp VA */
+ struct thread_struct_uw *host_uw; /* hyp VA */
struct task_struct *parent_task;

struct {
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index f77371232d8c..78781333ee26 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -152,7 +152,7 @@ struct thread_struct {
* Maintainers must ensure manually that this contains no
* implicit padding.
*/
- struct {
+ struct thread_struct_uw {
unsigned long tp_value; /* TLS register */
unsigned long tp2_value;
u64 fpmr;
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 826307e19e3a..8a0fedbb6f39 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -17,13 +17,13 @@
void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
{
struct task_struct *p = vcpu->arch.parent_task;
- struct user_fpsimd_state *fpsimd;
+ struct thread_struct_uw *uw;

if (!is_protected_kvm_enabled() || !p)
return;

- fpsimd = &p->thread.uw.fpsimd_state;
- kvm_unshare_hyp(fpsimd, fpsimd + 1);
+ uw = &p->thread.uw;
+ kvm_unshare_hyp(uw, uw + 1);
put_task_struct(p);
}

@@ -39,17 +39,16 @@ void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
{
int ret;
-
- struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
+ struct thread_struct_uw *uw = &current->thread.uw;

kvm_vcpu_unshare_task_fp(vcpu);

/* Make sure the host task fpsimd state is visible to hyp: */
- ret = kvm_share_hyp(fpsimd, fpsimd + 1);
+ ret = kvm_share_hyp(uw, uw + 1);
if (ret)
return ret;

- vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
+ vcpu->arch.host_uw = kern_hyp_va(uw);

/*
* We need to keep current's task_struct pinned until its data has been
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index e3fcf8c4d5b4..a9a11893c191 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -377,7 +377,7 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)

/* Write out the host state if it's in the registers */
if (vcpu->arch.fp_state == FP_STATE_HOST_OWNED)
- __fpsimd_save_state(vcpu->arch.host_fpsimd_state);
+ __fpsimd_save_state(&(vcpu->arch.host_uw->fpsimd_state));

/* Restore the guest state */
if (sve_guest)
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 2385fd03ed87..eb2208009875 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -42,7 +42,7 @@ static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
hyp_vcpu->vcpu.arch.fp_state = host_vcpu->arch.fp_state;

hyp_vcpu->vcpu.arch.debug_ptr = kern_hyp_va(host_vcpu->arch.debug_ptr);
- hyp_vcpu->vcpu.arch.host_fpsimd_state = host_vcpu->arch.host_fpsimd_state;
+ hyp_vcpu->vcpu.arch.host_uw = host_vcpu->arch.host_uw;

hyp_vcpu->vcpu.arch.vsesr_el2 = host_vcpu->arch.vsesr_el2;

@@ -64,7 +64,7 @@ static void sync_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
host_vcpu->arch.fault = hyp_vcpu->vcpu.arch.fault;

host_vcpu->arch.iflags = hyp_vcpu->vcpu.arch.iflags;
- host_vcpu->arch.fp_state = hyp_vcpu->vcpu.arch.fp_state;
+ host_vcpu->arch.host_uw = hyp_vcpu->vcpu.arch.host_uw;

host_cpu_if->vgic_hcr = hyp_cpu_if->vgic_hcr;
for (i = 0; i < hyp_cpu_if->used_lrs; ++i)

--
2.30.2