[PATCH v3 03/13] irqchip/gic-v3: Disable GICv4 features in protected KVM mode

[Fuad Tabba <fuad.tabba@linux.dev>]

From: Bartłomiej Grzesik <bgrzesik@google.com>

Later patches have the protected KVM hypervisor take the ITS from the
host and check each command the host queues. They don't emulate the
vLPI commands, as VMAPP's VPT_base, for one, is a host-chosen address
the ITS and the redistributors write to.

Clear has_vlpis and has_rvpeid at redistributor probe in protected mode,
so the host never issues a vLPI command, and print that GICv4 is off.
The host loses GICv4 direct injection for its non-protected guests,
which is off unless kvm-arm.vgic_v4_enable is set, and can't restore a
guest saved with GICD_TYPER2.nASSGIcap set.

The test is kvm_get_mode(), as the redistributors are probed before the
cpucaps are final. It lives in irq-gic-common.h as
gic_is_protected_kvm(), so that the ITS driver can use it too and
linux/kvm_host.h stays out of the rest of irqchip.

Signed-off-by: Bartłomiej Grzesik <bgrzesik@google.com>
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 Documentation/admin-guide/kernel-parameters.txt |  8 +++++---
 drivers/irqchip/irq-gic-common.h                | 13 +++++++++++++
 drivers/irqchip/irq-gic-v3.c                    |  8 ++++++++
 3 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0b3c140babd94..3e63e44609522 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3275,8 +3275,9 @@ Kernel parameters
 				hardware (with FEAT_NV2).
 
 			Defaults to VHE/nVHE based on hardware support. Setting
-			mode to "protected" will disable kexec and hibernation
-			for the host. To force nVHE on VHE hardware, add
+			mode to "protected" will disable kexec, hibernation and
+			GICv4 direct LPI injection for the host. To force nVHE
+			on VHE hardware, add
 			"arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" to the
 			command-line.
 			"nested" and "protected" are experimental and should be
@@ -3296,7 +3297,8 @@ Kernel parameters
 
 	kvm-arm.vgic_v4_enable=
 			[KVM,ARM,EARLY] Allow use of GICv4 for direct
-			injection of LPIs.
+			injection of LPIs. Has no effect when
+			kvm-arm.mode=protected.
 
 	kvm-arm.wfe_trap_policy=
 			[KVM,ARM] Control when to set WFE instruction trap for
diff --git a/drivers/irqchip/irq-gic-common.h b/drivers/irqchip/irq-gic-common.h
index 710cab61d9195..87b5c57dec0f1 100644
--- a/drivers/irqchip/irq-gic-common.h
+++ b/drivers/irqchip/irq-gic-common.h
@@ -10,6 +10,9 @@
 #include <linux/irqdomain.h>
 #include <linux/msi.h>
 #include <linux/irqchip/arm-gic-common.h>
+#ifdef CONFIG_ARM64
+#include <linux/kvm_host.h>
+#endif
 
 struct gic_quirk {
 	const char *desc;
@@ -29,6 +32,16 @@ void gic_enable_quirks(u32 iidr, const struct gic_quirk *quirks,
 void gic_enable_of_quirks(const struct device_node *np,
 			  const struct gic_quirk *quirks, void *data);
 
+#ifdef CONFIG_ARM64
+/* Not is_protected_kvm_enabled(): the GIC probes before the cpucaps are final. */
+static inline bool gic_is_protected_kvm(void)
+{
+	return kvm_get_mode() == KVM_MODE_PROTECTED;
+}
+#else
+static inline bool gic_is_protected_kvm(void) { return false; }
+#endif
+
 #define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING    (1 << 0)
 #define RDIST_FLAGS_RD_TABLES_PREALLOCATED     (1 << 1)
 #define RDIST_FLAGS_FORCE_NON_SHAREABLE        (1 << 2)
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 94873646d46fb..30ed17f26a208 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -1123,6 +1123,14 @@ static void gic_update_rdist_properties(void)
 	gic_iterate_rdists(__gic_update_rdist_properties);
 	if (WARN_ON(gic_data.ppi_nr == UINT_MAX))
 		gic_data.ppi_nr = 0;
+
+	/* Protected KVM doesn't emulate the vLPI commands. */
+	if (gic_is_protected_kvm() && gic_data.rdists.has_vlpis) {
+		pr_info("GICv4 features disabled in protected KVM mode\n");
+		gic_data.rdists.has_vlpis = false;
+		gic_data.rdists.has_rvpeid = false;
+	}
+
 	pr_info("GICv3 features: %d PPIs%s%s\n",
 		gic_data.ppi_nr,
 		gic_data.has_rss ? ", RSS" : "",
-- 
2.47.3