On 04/10/2024 16:27, Steven Price wrote:
MMIO emulation for a realm cannot be done directly with the VM's
registers as they are protected from the host. However, for emulatable
data aborts, the RMM uses GPRS[0] to provide the read/written value.
We can transfer this from/to the equivalent VCPU's register entry and
then depend on the generic MMIO handling code in KVM.
For a MMIO read, the value is placed in the shared RecExit structure
during kvm_handle_mmio_return() rather than in the VCPU's register
entry.
Signed-off-by: Steven Price <steven.price@xxxxxxx>
---
v3: Adapt to previous patch changes
---
arch/arm64/kvm/mmio.c | 10 +++++++++-
arch/arm64/kvm/rme-exit.c | 6 ++++++
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c
index cd6b7b83e2c3..66a838b3776a 100644
--- a/arch/arm64/kvm/mmio.c
+++ b/arch/arm64/kvm/mmio.c
@@ -6,6 +6,7 @@
#include <linux/kvm_host.h>
#include <asm/kvm_emulate.h>
+#include <asm/rmi_smc.h>
#include <trace/events/kvm.h>
#include "trace.h"
@@ -90,6 +91,9 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
vcpu->mmio_needed = 0;
+ if (vcpu_is_rec(vcpu))
+ vcpu->arch.rec.run->enter.flags |= REC_ENTER_EMULATED_MMIO;
+
if (!kvm_vcpu_dabt_iswrite(vcpu)) {
struct kvm_run *run = vcpu->run;
Should we additionally handle injecting an abort if there was no valid
syndrome information ? Like we do for protected VMs and normal VMs when
userspace doesn't offer to help ?
@@ -108,7 +112,11 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
&data);
data = vcpu_data_host_to_guest(vcpu, data, len);
- vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data);
+
+ if (vcpu_is_rec(vcpu))
+ vcpu->arch.rec.run->enter.gprs[0] = data;
I wonder if we can skip this here and we can sync the "enter.gprs[]"
from vcpu state at rec_enter, similar to what we do for PSCI/HOST call
exits. Also the ESR_ELx_SRT is always x0 for a Realm exit. So, we should
always find the enter.gpr[0] in vcpu.regs[0] at rec_enter.
Suzuki
+ else
+ vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data);
}
/*
diff --git a/arch/arm64/kvm/rme-exit.c b/arch/arm64/kvm/rme-exit.c
index e96ea308212c..1ddbff123149 100644
--- a/arch/arm64/kvm/rme-exit.c
+++ b/arch/arm64/kvm/rme-exit.c
@@ -25,6 +25,12 @@ static int rec_exit_reason_notimpl(struct kvm_vcpu *vcpu)
static int rec_exit_sync_dabt(struct kvm_vcpu *vcpu)
{
+ struct realm_rec *rec = &vcpu->arch.rec;
+
+ if (kvm_vcpu_dabt_iswrite(vcpu) && kvm_vcpu_dabt_isvalid(vcpu))
+ vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu),
+ rec->run->exit.gprs[0]);
+
return kvm_handle_guest_abort(vcpu);
}
