[PATCH v2 2/5] KVM: arm64: Exclude host_debug_data from vcpu_arch

Marc Zyngier
2024-03-22T17:10:09Z

Keeping host_debug_state on a per-vcpu basis is completely
pointless. The lifetime of this data is only that of the inner
run-loop, which means it is never accessed outside of the core
EL2 code.

Move the structure into kvm_host_data, and save over 500 bytes
per vcpu.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 31 +++++++++++++----------
arch/arm64/kvm/hyp/include/hyp/debug-sr.h | 4 +--
arch/arm64/kvm/hyp/nvhe/debug-sr.c | 8 +++---
3 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index ca6ef663950d..8c149e4ae99d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -543,6 +543,19 @@ struct kvm_cpu_context {
*/
struct kvm_host_data {
struct kvm_cpu_context host_ctxt;
+
+ /*
+ * host_debug_state contains the host registers which are
+ * saved and restored during world switches.
+ */
+ struct {
+ /* {Break,watch}point registers */
+ struct kvm_guest_debug_arch regs;
+ /* Statistical profiling extension */
+ u64 pmscr_el1;
+ /* Self-hosted trace */
+ u64 trfcr_el1;
+ } host_debug_state;
};

struct kvm_host_psci_config {
@@ -637,11 +650,10 @@ struct kvm_vcpu_arch {
* We maintain more than a single set of debug registers to support
* debugging the guest from the host and to maintain separate host and
* guest state during world switches. vcpu_debug_state are the debug
- * registers of the vcpu as the guest sees them. host_debug_state are
- * the host registers which are saved and restored during
- * world switches. external_debug_state contains the debug
- * values we want to debug the guest. This is set via the
- * KVM_SET_GUEST_DEBUG ioctl.
+ * registers of the vcpu as the guest sees them.
+ *
+ * external_debug_state contains the debug values we want to debug the
+ * guest. This is set via the KVM_SET_GUEST_DEBUG ioctl.
*
* debug_ptr points to the set of debug registers that should be loaded
* onto the hardware when running the guest.
@@ -653,15 +665,6 @@ struct kvm_vcpu_arch {
struct user_fpsimd_state *host_fpsimd_state; /* hyp VA */
struct task_struct *parent_task;

- struct {
- /* {Break,watch}point registers */
- struct kvm_guest_debug_arch regs;
- /* Statistical profiling extension */
- u64 pmscr_el1;
- /* Self-hosted trace */
- u64 trfcr_el1;
- } host_debug_state;
-
/* VGIC state */
struct vgic_cpu vgic_cpu;
struct arch_timer_cpu timer_cpu;
diff --git a/arch/arm64/kvm/hyp/include/hyp/debug-sr.h b/arch/arm64/kvm/hyp/include/hyp/debug-sr.h
index eec0f8ccda56..d00093699aaf 100644
--- a/arch/arm64/kvm/hyp/include/hyp/debug-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/debug-sr.h
@@ -137,7 +137,7 @@ static inline void __debug_switch_to_guest_common(struct kvm_vcpu *vcpu)

host_ctxt = host_data_ptr(host_ctxt);
guest_ctxt = &vcpu->arch.ctxt;
- host_dbg = &vcpu->arch.host_debug_state.regs;
+ host_dbg = host_data_ptr(host_debug_state.regs);
guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);

__debug_save_state(host_dbg, host_ctxt);
@@ -156,7 +156,7 @@ static inline void __debug_switch_to_host_common(struct kvm_vcpu *vcpu)

host_ctxt = host_data_ptr(host_ctxt);
guest_ctxt = &vcpu->arch.ctxt;
- host_dbg = &vcpu->arch.host_debug_state.regs;
+ host_dbg = host_data_ptr(host_debug_state.regs);
guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);

__debug_save_state(guest_dbg, guest_ctxt);
diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
index 7746ea507b6f..53efda0235cf 100644
--- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
@@ -83,10 +83,10 @@ void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
{
/* Disable and flush SPE data generation */
if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_SPE))
- __debug_save_spe(&vcpu->arch.host_debug_state.pmscr_el1);
+ __debug_save_spe(host_data_ptr(host_debug_state.pmscr_el1));
/* Disable and flush Self-Hosted Trace generation */
if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRBE))
- __debug_save_trace(&vcpu->arch.host_debug_state.trfcr_el1);
+ __debug_save_trace(host_data_ptr(host_debug_state.trfcr_el1));
}

void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
@@ -97,9 +97,9 @@ void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
void __debug_restore_host_buffers_nvhe(struct kvm_vcpu *vcpu)
{
if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_SPE))
- __debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1);
+ __debug_restore_spe(*host_data_ptr(host_debug_state.pmscr_el1));
if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRBE))
- __debug_restore_trace(vcpu->arch.host_debug_state.trfcr_el1);
+ __debug_restore_trace(*host_data_ptr(host_debug_state.trfcr_el1));
}

void __debug_switch_to_host(struct kvm_vcpu *vcpu)
--
2.39.2