[PATCH v2 19/43] KVM: arm64: Handle realm MMIO emulation

Steven Price
2024-04-12T08:44:03Z

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@arm.com>
---
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 200c8019a82a..589a1a7601ad 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->entry.flags |= RMI_EMULATED_MMIO;
+
if (!kvm_vcpu_dabt_iswrite(vcpu)) {
struct kvm_run *run = vcpu->run;

@@ -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->entry.gprs[0] = data;
+ 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 5bf58c9b42b7..2ddaec09cc98 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);
}

--
2.34.1