linux-kernel - [PATCH v3 2/6] bus: mhi: host: pci_generic: Read SUBSYSTEM_VENDOR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20250821-vdev_next-20250821_sriov-v3-2-e1b017c48d4a@quicinc.com>
Date: Thu, 21 Aug 2025 18:25:34 +0530
From: Vivek.Pernamitta@...cinc.com
To: Manivannan Sadhasivam <mani@...nel.org>
CC: <mhi@...ts.linux.dev>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Vivek Pernamitta <quic_vpernami@...cinc.com>,
        Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Subject: [PATCH v3 2/6] bus: mhi: host: pci_generic: Read
 SUBSYSTEM_VENDOR_ID for VF's to check status

From: Vivek Pernamitta <quic_vpernami@...cinc.com>

- In SR-IOV enabled devices, the VF DEVICE/VENDOR ID register returns
  FFFFh when read (as per PCIe SR-IOV spec section 3.4.1.1).
- To determine device activity, read the PCIe VENDOR_ID of the Physical
  Function (PF) instead.
- Disabled health check monitoring for Virtual Functions (VFs), as they
  are not physical functions and lack direct hardware control.
- This avoids unnecessary CPU cycles consumed by VF health checks, which
  are unintended and non-functional.

Signed-off-by: Vivek Pernamitta <quic_vpernami@...cinc.com>
Reviewed-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
---
 drivers/bus/mhi/host/pci_generic.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/drivers/bus/mhi/host/pci_generic.c b/drivers/bus/mhi/host/pci_generic.c
index 2967ed4cec29d1c1eeb581ed44cf9afcea90f533..df18627a9feb4f2d53ba1ca6a4e8087dc23c7873 100644
--- a/drivers/bus/mhi/host/pci_generic.c
+++ b/drivers/bus/mhi/host/pci_generic.c
@@ -1094,8 +1094,7 @@ static bool mhi_pci_is_alive(struct mhi_controller *mhi_cntrl)
 	struct pci_dev *pdev = to_pci_dev(mhi_cntrl->cntrl_dev);
 	u16 vendor = 0;
 
-	if (pci_read_config_word(pdev, PCI_VENDOR_ID, &vendor))
-		return false;
+	pci_read_config_word(pci_physfn(pdev), PCI_VENDOR_ID, &vendor);
 
 	if (vendor == (u16) ~0 || vendor == 0)
 		return false;
@@ -1205,7 +1204,9 @@ static void mhi_pci_recovery_work(struct work_struct *work)
 
 	dev_warn(&pdev->dev, "device recovery started\n");
 
-	timer_delete(&mhi_pdev->health_check_timer);
+	if (pdev->is_physfn)
+		timer_delete(&mhi_pdev->health_check_timer);
+
 	pm_runtime_forbid(&pdev->dev);
 
 	/* Clean up MHI state */
@@ -1232,7 +1233,10 @@ static void mhi_pci_recovery_work(struct work_struct *work)
 	dev_dbg(&pdev->dev, "Recovery completed\n");
 
 	set_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status);
-	mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
+
+	if (pdev->is_physfn)
+		mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
+
 	return;
 
 err_unprepare:
@@ -1319,7 +1323,9 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	else
 		mhi_cntrl_config = info->config;
 
-	timer_setup(&mhi_pdev->health_check_timer, health_check, 0);
+	/* Initialize health check monitor only for Physical functions */
+	if (pdev->is_physfn)
+		timer_setup(&mhi_pdev->health_check_timer, health_check, 0);
 
 	mhi_cntrl = &mhi_pdev->mhi_cntrl;
 
@@ -1383,7 +1389,8 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	set_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status);
 
 	/* start health check */
-	mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
+	if (pdev->is_physfn)
+		mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
 
 	/* Allow runtime suspend only if both PME from D3Hot and M3 are supported */
 	if (pci_pme_capable(pdev, PCI_D3hot) && !(info->no_m3)) {
@@ -1408,7 +1415,8 @@ static void mhi_pci_remove(struct pci_dev *pdev)
 	struct mhi_pci_device *mhi_pdev = pci_get_drvdata(pdev);
 	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
 
-	timer_delete_sync(&mhi_pdev->health_check_timer);
+	if (pdev->is_physfn)
+		timer_delete_sync(&mhi_pdev->health_check_timer);
 	cancel_work_sync(&mhi_pdev->recovery_work);
 
 	if (test_and_clear_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status)) {
@@ -1436,7 +1444,8 @@ static void mhi_pci_reset_prepare(struct pci_dev *pdev)
 
 	dev_info(&pdev->dev, "reset\n");
 
-	timer_delete(&mhi_pdev->health_check_timer);
+	if (pdev->is_physfn)
+		timer_delete(&mhi_pdev->health_check_timer);
 
 	/* Clean up MHI state */
 	if (test_and_clear_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status)) {
@@ -1481,7 +1490,8 @@ static void mhi_pci_reset_done(struct pci_dev *pdev)
 	}
 
 	set_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status);
-	mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
+	if (pdev->is_physfn)
+		mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
 }
 
 static pci_ers_result_t mhi_pci_error_detected(struct pci_dev *pdev,
@@ -1546,7 +1556,9 @@ static int  __maybe_unused mhi_pci_runtime_suspend(struct device *dev)
 	if (test_and_set_bit(MHI_PCI_DEV_SUSPENDED, &mhi_pdev->status))
 		return 0;
 
-	timer_delete(&mhi_pdev->health_check_timer);
+	if (pdev->is_physfn)
+		timer_delete(&mhi_pdev->health_check_timer);
+
 	cancel_work_sync(&mhi_pdev->recovery_work);
 
 	if (!test_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status) ||
@@ -1597,7 +1609,8 @@ static int __maybe_unused mhi_pci_runtime_resume(struct device *dev)
 	}
 
 	/* Resume health check */
-	mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
+	if (pdev->is_physfn)
+		mod_timer(&mhi_pdev->health_check_timer, jiffies + HEALTH_CHECK_PERIOD);
 
 	/* It can be a remote wakeup (no mhi runtime_get), update access time */
 	pm_runtime_mark_last_busy(dev);

-- 
2.34.1