[PATCH] KVM: selftests: Add SYNC after guest ITS setup in vgic_lpi_stress

[Maximilian Dittgen]

vgic_lpi_stress sends MAPTI and MAPC commands during guest GIC
setup to map interrupt events to ITT entries and collection IDs
to redistributors, respectively.

Theoretically, we have no guarantee that the ITS will
finish handling these mapping commands before the selftest
calls KVM_SIGNAL_MSI to inject LPIs to the guest. If LPIs
are injected before ITS mapping completes, the ITS cannot
properly pass the interrupt on to the redistributor.

In practice, KVM processes ITS commands synchronously, so
SYNC calls are functionally unnecessary and ignored in
vgic_its_handle_command().

However, selftests should test based on ARM specification and
be blind to KVM-specific implementation optimizations. Thus,
we must update the test to be architecturally compliant and
logically correct.

Fix by adding a SYNC command to the selftests ITS library,
then calling SYNC after ITS mapping to ensure mapping
completes before signal_lpi() writes to GITS_TRANSLATER.

This patch depends on commit a24f7afce048 ("KVM: selftests:
fix MAPC RDbase target formatting in vgic_lpi_stress"), which
is queued in kvmarm/fixes.

Signed-off-by: Maximilian Dittgen <mdittgen at amazon.de>
---
Validated by the following debug logging to the GITS_CMD_SYNC handler
in vgic_its_handle_command():

        kvm_info("ITS SYNC command: %016llx %016llx %016llx %016llx\n",
            its_cmd[0], its_cmd[1], its_cmd[2], its_cmd[3]);

Initialized a selftest guest with 4 vCPUs by:

        ./vgic_lpi_stress -v 4

Confirmed that an ITS SYNC was successfully called for all 4 vCPUs:

        kvm [5094]: ITS SYNC command: 0000000000000005 0000000000000000 0000000000000000 0000000000000000
        kvm [5094]: ITS SYNC command: 0000000000000005 0000000000000000 0000000000010000 0000000000000000
        kvm [5094]: ITS SYNC command: 0000000000000005 0000000000000000 0000000000020000 0000000000000000
        kvm [5094]: ITS SYNC command: 0000000000000005 0000000000000000 0000000000030000 0000000000000000
---
 tools/testing/selftests/kvm/arm64/vgic_lpi_stress.c   |  4 ++++
 .../testing/selftests/kvm/include/arm64/gic_v3_its.h  |  1 +
 tools/testing/selftests/kvm/lib/arm64/gic_v3_its.c    | 11 +++++++++++
 3 files changed, 16 insertions(+)

diff --git a/tools/testing/selftests/kvm/arm64/vgic_lpi_stress.c b/tools/testing/selftests/kvm/arm64/vgic_lpi_stress.c
index 687d04463983..e857a605f577 100644
--- a/tools/testing/selftests/kvm/arm64/vgic_lpi_stress.c
+++ b/tools/testing/selftests/kvm/arm64/vgic_lpi_stress.c
@@ -118,6 +118,10 @@ static void guest_setup_gic(void)
 
 	guest_setup_its_mappings();
 	guest_invalidate_all_rdists();
+
+	/* SYNC to ensure ITS setup is complete */
+	for (cpuid = 0; cpuid < test_data.nr_cpus; cpuid++)
+		its_send_sync_cmd(test_data.cmdq_base_va, cpuid);
 }
 
 static void guest_code(size_t nr_lpis)
diff --git a/tools/testing/selftests/kvm/include/arm64/gic_v3_its.h b/tools/testing/selftests/kvm/include/arm64/gic_v3_its.h
index 3722ed9c8f96..58feef3eb386 100644
--- a/tools/testing/selftests/kvm/include/arm64/gic_v3_its.h
+++ b/tools/testing/selftests/kvm/include/arm64/gic_v3_its.h
@@ -15,5 +15,6 @@ void its_send_mapc_cmd(void *cmdq_base, u32 vcpu_id, u32 collection_id, bool val
 void its_send_mapti_cmd(void *cmdq_base, u32 device_id, u32 event_id,
 			u32 collection_id, u32 intid);
 void its_send_invall_cmd(void *cmdq_base, u32 collection_id);
+void its_send_sync_cmd(void *cmdq_base, u32 vcpu_id);
 
 #endif // __SELFTESTS_GIC_V3_ITS_H__
diff --git a/tools/testing/selftests/kvm/lib/arm64/gic_v3_its.c b/tools/testing/selftests/kvm/lib/arm64/gic_v3_its.c
index 0e2f8ed90f30..d9ee331074ea 100644
--- a/tools/testing/selftests/kvm/lib/arm64/gic_v3_its.c
+++ b/tools/testing/selftests/kvm/lib/arm64/gic_v3_its.c
@@ -253,3 +253,14 @@ void its_send_invall_cmd(void *cmdq_base, u32 collection_id)
 
 	its_send_cmd(cmdq_base, &cmd);
 }
+
+void its_send_sync_cmd(void *cmdq_base, u32 vcpu_id)
+{
+	struct its_cmd_block cmd = {};
+
+	its_encode_cmd(&cmd, GITS_CMD_SYNC);
+	its_encode_target(&cmd, procnum_to_rdbase(vcpu_id));
+
+	its_send_cmd(cmdq_base, &cmd);
+}
+
-- 
2.50.1 (Apple Git-155)




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