[PATCH 4/4] firmware: arm_ffa: Defer probe until pKVM is initialized

[Sudeep Holla]

When protected KVM is enabled, the kernel includes a pKVM FF-A proxy
that sits in front of the normal FF-A driver. The proxy has to perform
its own FF-A version negotiation and setup first, so that it can mediate
subsequent FF-A traffic correctly.

Defer FF-A core probing until pKVM has completed initialization. This
keeps the normal driver from negotiating the FF-A version or performing
other transport setup before the pKVM proxy is ready, and lets the
driver model retry probing once the protected KVM state required by the
FF-A transport is available.

Suggested-by: Yeoreum Yun <yeoreum.yun at arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla at kernel.org>
---
 drivers/firmware/arm_ffa/driver.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index e9d7dc71c06d..1fba064c2aba 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -43,6 +43,8 @@
 #include <linux/uuid.h>
 #include <linux/xarray.h>
 
+#include <asm/virt.h>
+
 #include "common.h"
 
 #define FFA_DRIVER_VERSION	FFA_VERSION_1_2
@@ -2039,6 +2041,10 @@ static int ffa_probe(struct platform_device *pdev)
 	u32 buf_sz;
 	size_t rxtx_bufsz = SZ_4K;
 
+	if (IS_BUILTIN(CONFIG_ARM_FFA_TRANSPORT) &&
+	    is_protected_kvm_enabled() && !is_pkvm_initialized())
+		return -EPROBE_DEFER;
+
 	ret = ffa_transport_init(&invoke_ffa_fn);
 	if (ret)
 		return ret;

-- 
2.43.0