linux-kernel - [PATCH v4 19/43] KVM: arm64: Handle realm MMIO emulation

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Message-Id: <20240821153844.60084-20-steven.price@arm.com>
Date: Wed, 21 Aug 2024 16:38:20 +0100
From: Steven Price <steven.price@....com>
To: kvm@...r.kernel.org,
	kvmarm@...ts.linux.dev
Cc: Steven Price <steven.price@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>,
	Will Deacon <will@...nel.org>,
	James Morse <james.morse@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Joey Gouly <joey.gouly@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Christoffer Dall <christoffer.dall@....com>,
	Fuad Tabba <tabba@...gle.com>,
	linux-coco@...ts.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
	Gavin Shan <gshan@...hat.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Alper Gun <alpergun@...gle.com>
Subject: [PATCH v4 19/43] KVM: arm64: Handle realm MMIO emulation

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@....com>
---
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..dbd06ca368e8 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 |= 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->enter.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 f4e45d475798..03ed147f7926 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