linux-kernel - [PATCH v2 05/16] KVM: arm64: Plumb MMIO checking into the fault handling

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Date:   Mon,  4 Oct 2021 18:48:38 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     will@...nel.org, qperret@...gle.com, dbrazdil@...gle.com,
        Steven Price <steven.price@....com>,
        Andrew Jones <drjones@...hat.com>,
        Fuad Tabba <tabba@...gle.com>,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Shanker R Donthineni <sdonthineni@...dia.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: [PATCH v2 05/16] KVM: arm64: Plumb MMIO checking into the fault handling

Plumb the MMIO checking code into the MMIO fault handling code.
Nothing allows a region to be registered yet, so there should be
no funtional change either.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/kvm/mmio.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c
index 3dd38a151d2a..dfa375823264 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/kvm_mmu.h>
 #include <trace/events/kvm.h>
 
 #include "trace.h"
@@ -135,6 +136,13 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
 	 * volunteered to do so, and bail out otherwise.
 	 */
 	if (!kvm_vcpu_dabt_isvalid(vcpu)) {
+		/* With MMIO guard enabled, the guest should know better */
+		if (test_bit(KVM_ARCH_FLAG_MMIO_GUARD,
+			     &vcpu->kvm->arch.flags)) {
+			kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
+			return 1;
+		}
+
 		if (test_bit(KVM_ARCH_FLAG_RETURN_NISV_IO_ABORT_TO_USER,
 			     &vcpu->kvm->arch.flags)) {
 			run->exit_reason = KVM_EXIT_ARM_NISV;
@@ -156,6 +164,15 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
 	len = kvm_vcpu_dabt_get_as(vcpu);
 	rt = kvm_vcpu_dabt_get_rd(vcpu);
 
+	/* Check failed? Return to the guest for debriefing... */
+	if (!kvm_check_ioguard_page(vcpu, fault_ipa))
+		return 1;
+
+	/* If we cross a page boundary, check that too... */
+	if (((fault_ipa + len - 1) & PAGE_MASK) != (fault_ipa & PAGE_MASK) &&
+	    !kvm_check_ioguard_page(vcpu, fault_ipa + len - 1))
+		return 1;
+
 	if (is_write) {
 		data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt),
 					       len);
-- 
2.30.2