linux-kernel - [RFC PATCH 15/28] KVM: arm64: Handle realm MMIO emulation

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Date:   Fri, 27 Jan 2023 11:29:19 +0000
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
Subject: [RFC PATCH 15/28] 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 the RMM interface
provides a structure member for providing the read/written value and
we can transfer this to the appropriate VCPU's register entry and then
depend on the generic MMIO handling code in KVM.

Signed-off-by: Steven Price <steven.price@....com>
---
 arch/arm64/kvm/mmio.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c
index 3dd38a151d2a..c4879fa3a8d3 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"
@@ -109,6 +110,9 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
 			       &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;
 	}
 
 	/*
@@ -179,6 +183,9 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
 	run->mmio.len		= len;
 	vcpu->mmio_needed	= 1;
 
+	if (vcpu_is_rec(vcpu))
+		vcpu->arch.rec.run->entry.flags |= RMI_EMULATED_MMIO;
+
 	if (!ret) {
 		/* We handled the access successfully in the kernel. */
 		if (!is_write)
-- 
2.34.1