PCI/MSI: Protect msi_desc::masked for multi-MSI

commit 77e89afc25f30abd56e76a809ee2884d7c1b63ce upstream.

Multi-MSI uses a single MSI descriptor and there is a single mask register
when the device supports per vector masking. To avoid reading back the mask
register the value is cached in the MSI descriptor and updates are done by
clearing and setting bits in the cache and writing it to the device.

But nothing protects msi_desc::masked and the mask register from being
modified concurrently on two different CPUs for two different Linux
interrupts which belong to the same multi-MSI descriptor.

Add a lock to struct device and protect any operation on the mask and the
mask register with it.

This makes the update of msi_desc::masked unconditional, but there is no
place which requires a modification of the hardware register without
updating the masked cache.

msi_mask_irq() is now an empty wrapper which will be cleaned up in follow
up changes.

The problem goes way back to the initial support of multi-MSI, but picking
the commit which introduced the mask cache is a valid cut off point
(2.6.30).

Fixes: f2440d9acbe8 ("PCI MSI: Refactor interrupt masking code")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210729222542.726833414@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 3b8487e28c84fd61fa2f7347105aece423f4c05d..e82a89325f3d65bf9076c005a84fe9c458530d39 100644 (file)
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -710,6 +710,7 @@ void device_initialize(struct device *dev)
        device_pm_init(dev);
        set_dev_node(dev, -1);
 #ifdef CONFIG_GENERIC_MSI_IRQ
+       raw_spin_lock_init(&dev->msi_lock);
        INIT_LIST_HEAD(&dev->msi_list);
 #endif
 }

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index b3977b4c51b637382ddc8362ec89aab6deaef982..79b36f1bde0ded55042f2cadc5fb42e0387261b9 100644 (file)
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -189,24 +189,25 @@ static inline __attribute_const__ u32 msi_mask(unsigned x)
  * reliably as devices without an INTx disable bit will then generate a
  * level IRQ which will never be cleared.
  */
-u32 __pci_msi_desc_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
+void __pci_msi_desc_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
 {
-       u32 mask_bits = desc->masked;
+       raw_spinlock_t *lock = &desc->dev->msi_lock;
+       unsigned long flags;
 
        if (pci_msi_ignore_mask || !desc->msi_attrib.maskbit)
-               return 0;
+               return;
 
-       mask_bits &= ~mask;
-       mask_bits |= flag;
+       raw_spin_lock_irqsave(lock, flags);
+       desc->masked &= ~mask;
+       desc->masked |= flag;
        pci_write_config_dword(msi_desc_to_pci_dev(desc), desc->mask_pos,
-                              mask_bits);
-
-       return mask_bits;
+                              desc->masked);
+       raw_spin_unlock_irqrestore(lock, flags);
 }
 
 static void msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
 {
-       desc->masked = __pci_msi_desc_mask_irq(desc, mask, flag);
+       __pci_msi_desc_mask_irq(desc, mask, flag);
 }
 
 static void __iomem *pci_msix_desc_addr(struct msi_desc *desc)

diff --git a/include/linux/device.h b/include/linux/device.h
index eb865b461acc4b5f3c7e9b5bb1d70a7dd2be5056..ca765188a98148219a26e25f82c6991ad22b49de 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -812,6 +812,7 @@ struct device {
        struct dev_pin_info     *pins;
 #endif
 #ifdef CONFIG_GENERIC_MSI_IRQ
+       raw_spinlock_t          msi_lock;
        struct list_head        msi_list;
 #endif
 

diff --git a/include/linux/msi.h b/include/linux/msi.h
index debc8aa4ec1978273262ce605156eb850ddc9190..601bff9fbbec21b4d10d8c79110be32e1a63526a 100644 (file)
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -133,7 +133,7 @@ void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
 void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg);
 
 u32 __pci_msix_desc_mask_irq(struct msi_desc *desc, u32 flag);
-u32 __pci_msi_desc_mask_irq(struct msi_desc *desc, u32 mask, u32 flag);
+void __pci_msi_desc_mask_irq(struct msi_desc *desc, u32 mask, u32 flag);
 void pci_msi_mask_irq(struct irq_data *data);
 void pci_msi_unmask_irq(struct irq_data *data);