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Subject[PATCH v2 08/18] arm64: KVM: add support to save/restore SPE profiling buffer controls
Date
From: Sudeep Holla <sudeep.holla@arm.com>

Currently since we don't support profiling using SPE in the guests,
we just save the PMSCR_EL1, flush the profiling buffers and disable
sampling. However in order to support simultaneous sampling both in
the host and guests, we need to save and reatore the complete SPE
profiling buffer controls' context.

Let's add the support for the same and keep it disabled for now.
We can enable it conditionally only if guests are allowed to use
SPE.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
[ Clear PMBSR bit when saving state to prevent spurious interrupts ]
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
---
arch/arm64/kvm/hyp/debug-sr.c | 51 +++++++++++++++++++++++++++++------
1 file changed, 43 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c
index 8a70a493345e..12429b212a3a 100644
--- a/arch/arm64/kvm/hyp/debug-sr.c
+++ b/arch/arm64/kvm/hyp/debug-sr.c
@@ -85,7 +85,8 @@
default: write_debug(ptr[0], reg, 0); \
}

-static void __hyp_text __debug_save_spe_nvhe(struct kvm_cpu_context *ctxt)
+static void __hyp_text
+__debug_save_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt)
{
u64 reg;

@@ -102,22 +103,46 @@ static void __hyp_text __debug_save_spe_nvhe(struct kvm_cpu_context *ctxt)
if (reg & BIT(SYS_PMBIDR_EL1_P_SHIFT))
return;

- /* No; is the host actually using the thing? */
- reg = read_sysreg_s(SYS_PMBLIMITR_EL1);
- if (!(reg & BIT(SYS_PMBLIMITR_EL1_E_SHIFT)))
+ /* Save the control register and disable data generation */
+ ctxt->sys_regs[PMSCR_EL1] = read_sysreg_el1(SYS_PMSCR);
+
+ if (!ctxt->sys_regs[PMSCR_EL1])
return;

/* Yes; save the control register and disable data generation */
- ctxt->sys_regs[PMSCR_EL1] = read_sysreg_el1(SYS_PMSCR);
write_sysreg_el1(0, SYS_PMSCR);
isb();

/* Now drain all buffered data to memory */
psb_csync();
dsb(nsh);
+
+ if (!full_ctxt)
+ return;
+
+ ctxt->sys_regs[PMBLIMITR_EL1] = read_sysreg_s(SYS_PMBLIMITR_EL1);
+ write_sysreg_s(0, SYS_PMBLIMITR_EL1);
+
+ /*
+ * As PMBSR is conditionally restored when returning to the host we
+ * must ensure the service bit is unset here to prevent a spurious
+ * host SPE interrupt from being raised.
+ */
+ ctxt->sys_regs[PMBSR_EL1] = read_sysreg_s(SYS_PMBSR_EL1);
+ write_sysreg_s(0, SYS_PMBSR_EL1);
+
+ isb();
+
+ ctxt->sys_regs[PMSICR_EL1] = read_sysreg_s(SYS_PMSICR_EL1);
+ ctxt->sys_regs[PMSIRR_EL1] = read_sysreg_s(SYS_PMSIRR_EL1);
+ ctxt->sys_regs[PMSFCR_EL1] = read_sysreg_s(SYS_PMSFCR_EL1);
+ ctxt->sys_regs[PMSEVFR_EL1] = read_sysreg_s(SYS_PMSEVFR_EL1);
+ ctxt->sys_regs[PMSLATFR_EL1] = read_sysreg_s(SYS_PMSLATFR_EL1);
+ ctxt->sys_regs[PMBPTR_EL1] = read_sysreg_s(SYS_PMBPTR_EL1);
}

-static void __hyp_text __debug_restore_spe_nvhe(struct kvm_cpu_context *ctxt)
+static void __hyp_text
+__debug_restore_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt)
{
if (!ctxt->sys_regs[PMSCR_EL1])
return;
@@ -126,6 +151,16 @@ static void __hyp_text __debug_restore_spe_nvhe(struct kvm_cpu_context *ctxt)
isb();

/* Re-enable data generation */
+ if (full_ctxt) {
+ write_sysreg_s(ctxt->sys_regs[PMBPTR_EL1], SYS_PMBPTR_EL1);
+ write_sysreg_s(ctxt->sys_regs[PMBLIMITR_EL1], SYS_PMBLIMITR_EL1);
+ write_sysreg_s(ctxt->sys_regs[PMSFCR_EL1], SYS_PMSFCR_EL1);
+ write_sysreg_s(ctxt->sys_regs[PMSEVFR_EL1], SYS_PMSEVFR_EL1);
+ write_sysreg_s(ctxt->sys_regs[PMSLATFR_EL1], SYS_PMSLATFR_EL1);
+ write_sysreg_s(ctxt->sys_regs[PMSIRR_EL1], SYS_PMSIRR_EL1);
+ write_sysreg_s(ctxt->sys_regs[PMSICR_EL1], SYS_PMSICR_EL1);
+ write_sysreg_s(ctxt->sys_regs[PMBSR_EL1], SYS_PMBSR_EL1);
+ }
write_sysreg_el1(ctxt->sys_regs[PMSCR_EL1], SYS_PMSCR);
}

@@ -198,7 +233,7 @@ void __hyp_text __debug_restore_host_context(struct kvm_vcpu *vcpu)
guest_ctxt = &vcpu->arch.ctxt;

if (!has_vhe())
- __debug_restore_spe_nvhe(host_ctxt);
+ __debug_restore_spe_nvhe(host_ctxt, false);

if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
return;
@@ -222,7 +257,7 @@ void __hyp_text __debug_save_host_context(struct kvm_vcpu *vcpu)

host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
if (!has_vhe())
- __debug_save_spe_nvhe(host_ctxt);
+ __debug_save_spe_nvhe(host_ctxt, false);
}

void __hyp_text __debug_save_guest_context(struct kvm_vcpu *vcpu)
--
2.21.0
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