[PATCH v3 5/8] ath11k: use KVM MSI domain for VM passthrough

[Jose Ignacio Tornos Martinez]

The Qualcomm ath11k firmware programs MSI addresses directly into
device BAR registers for CE/SRNG ring interrupt delivery, bypassing
the standard PCI config MSI path managed by QEMU/VFIO. In a VM, the
firmware receives the guest virtual APIC address instead of the host
IRTE address, causing DMAR faults and non-functional interrupts.

When CONFIG_PCI_KVM_MSI_DOMAIN is enabled, use the KVM PCI MSI domain
synchronization functions to obtain the correct host physical MSI
address after MSI is enabled in power_up. The kvm_pci_msi_wait_ready()
function performs a KVM hypercall to retrieve the host MSI address,
and kvm_pci_msi_get_address() reads the cached values to update the
driver's internal MSI address/data used for ring configuration.

This placement (after msi_enable in power_up) ensures:
- Host MSI is enabled and stable (QEMU has completed setup)
- No MSI state transitions are in progress
- CE/SRNG rings have not been programmed yet
- The function runs on every power_up, including recovery

On baremetal, if CONFIG_PCI_KVM_MSI_DOMAIN is not enabled the code is
compiled out and the behavior is identical to the original. If
CONFIG_PCI_KVM_MSI_DOMAIN is enabled (e.g. distribution kernels), the
KVM MSI functions detect baremetal at runtime and return immediately,
preserving the original behavior with no side effects.

Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@xxxxxxxxxx>
---
v3: new
v2: https://lore.kernel.org/all/20261011074514.515894-1-jtornosm@xxxxxxxxxx/

 drivers/net/wireless/ath/ath11k/pci.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/wireless/ath/ath11k/pci.c b/drivers/net/wireless/ath/ath11k/pci.c
index 7e29ebaf9773..31889e5caa8d 100644
--- a/drivers/net/wireless/ath/ath11k/pci.c
+++ b/drivers/net/wireless/ath/ath11k/pci.c
@@ -7,6 +7,9 @@
 #include <linux/module.h>
 #include <linux/msi.h>
 #include <linux/pci.h>
+#if IS_ENABLED(CONFIG_PCI_KVM_MSI_DOMAIN)
+#include <linux/pci-kvm-msi.h>
+#endif
 #include <linux/of.h>
 #include <linux/time.h>
 #include <linux/vmalloc.h>
@@ -855,6 +858,13 @@ static int ath11k_pci_power_up(struct ath11k_base *ab)
 
 	ath11k_pci_msi_enable(ab_pci);
 
+#if IS_ENABLED(CONFIG_PCI_KVM_MSI_DOMAIN)
+	if (kvm_pci_msi_wait_ready(ab_pci->pdev, 500) > 0)
+		kvm_pci_msi_get_address(ab_pci->pdev, &ab->pci.msi.addr_lo,
+					&ab->pci.msi.addr_hi,
+					&ab->pci.msi.ep_base_data);
+#endif
+
 	ret = ath11k_mhi_start(ab_pci);
 	if (ret) {
 		ath11k_err(ab, "failed to start mhi: %d\n", ret);
@@ -1350,6 +1360,9 @@ module_exit(ath11k_pci_exit);
 
 MODULE_DESCRIPTION("Driver support for Qualcomm Technologies PCIe 802.11ax WLAN devices");
 MODULE_LICENSE("Dual BSD/GPL");
+#if IS_ENABLED(CONFIG_PCI_KVM_MSI_DOMAIN)
+MODULE_SOFTDEP("pre: pci-kvm-msi");
+#endif
 
 /* firmware files */
 MODULE_FIRMWARE(ATH11K_FW_DIR "/QCA6390/hw2.0/*");
-- 
2.56.0