[PATCH v4 1/4] PCI/MSI: Conservatively generalize no_64bit_msi into msi_addr_mask

Vivian Wang
2026-01-29T01:56:54Z

Some PCI devices have PCI_MSI_FLAGS_64BIT in the MSI capability, but
implement less than 64 address bits. This breaks on platforms where such
a device is assigned an MSI address higher than what's reachable.

Currently, the no_64bit_msi bit is set for these devices, meaning that
only 32-bit MSI addresses are allowed for them. However, on some
platforms the MSI doorbell address is above the 32-bit limit but within
the addressable range of the device.

As a first step to enabling MSI on those combinations of devices and
platforms, conservatively generalize the single-bit flag no_64bit_msi
into msi_addr_mask. (The name msi_addr_mask is chosen to avoid confusion
with msi_mask.)

The translation is essentially:

- no_64bit_msi = 1 -> msi_addr_mask = DMA_BIT_MASK(32)
- no_64bit_msi = 0 -> msi_addr_mask = DMA_BIT_MASK(64)
- if (no_64bit_msi) -> if (msi_addr_mask < DMA_BIT_MASK(64))

Since no values other than DMA_BIT_MASK(32) and DMA_BIT_MASK(64) are
used, no functional change is intended. Future patches that make use of
intermediate values of msi_addr_mask will follow, allowing devices that
cannot use full 64-bit addresses for MSI to work on platforms with MSI
doorbell above the 32-bit limit.

Acked-by: Takashi Iwai <tiwai@suse.de> # sound
Reviewed-by: Brett Creeley <brett.creeley@amd.com> # ionic
Reviewed-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Vivian Wang <wangruikang@iscas.ac.cn>
---
v4: Patch message rewording (Thomas)

checkpatch complains about the comment include/linux/pci.h, which I have
formatted similarly with other comments in the vicinity.
---
arch/powerpc/platforms/powernv/pci-ioda.c | 2 +-
arch/powerpc/platforms/pseries/msi.c | 4 ++--
drivers/gpu/drm/radeon/radeon_irq_kms.c | 2 +-
drivers/net/ethernet/pensando/ionic/ionic_bus_pci.c | 2 +-
drivers/pci/msi/msi.c | 2 +-
drivers/pci/msi/pcidev_msi.c | 2 +-
drivers/pci/probe.c | 7 +++++++
include/linux/pci.h | 8 +++++++-
sound/hda/controllers/intel.c | 2 +-
9 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index b0c1d9d16fb5..1c78fdfb7b03 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1666,7 +1666,7 @@ static int __pnv_pci_ioda_msi_setup(struct pnv_phb *phb, struct pci_dev *dev,
return -ENXIO;

/* Force 32-bit MSI on some broken devices */
- if (dev->no_64bit_msi)
+ if (dev->msi_addr_mask < DMA_BIT_MASK(64))
is_64 = 0;

/* Assign XIVE to PE */
diff --git a/arch/powerpc/platforms/pseries/msi.c b/arch/powerpc/platforms/pseries/msi.c
index a82aaa786e9e..7473c7ca1db0 100644
--- a/arch/powerpc/platforms/pseries/msi.c
+++ b/arch/powerpc/platforms/pseries/msi.c
@@ -383,7 +383,7 @@ static int rtas_prepare_msi_irqs(struct pci_dev *pdev, int nvec_in, int type,
*/
again:
if (type == PCI_CAP_ID_MSI) {
- if (pdev->no_64bit_msi) {
+ if (pdev->msi_addr_mask < DMA_BIT_MASK(64)) {
rc = rtas_change_msi(pdn, RTAS_CHANGE_32MSI_FN, nvec);
if (rc < 0) {
/*
@@ -409,7 +409,7 @@ static int rtas_prepare_msi_irqs(struct pci_dev *pdev, int nvec_in, int type,
if (use_32bit_msi_hack && rc > 0)
rtas_hack_32bit_msi_gen2(pdev);
} else {
- if (pdev->no_64bit_msi)
+ if (pdev->msi_addr_mask < DMA_BIT_MASK(64))
rc = rtas_change_msi(pdn, RTAS_CHANGE_32MSIX_FN, nvec);
else
rc = rtas_change_msi(pdn, RTAS_CHANGE_MSIX_FN, nvec);
diff --git a/drivers/gpu/drm/radeon/radeon_irq_kms.c b/drivers/gpu/drm/radeon/radeon_irq_kms.c
index 9961251b44ba..d550554a6f3f 100644
--- a/drivers/gpu/drm/radeon/radeon_irq_kms.c
+++ b/drivers/gpu/drm/radeon/radeon_irq_kms.c
@@ -252,7 +252,7 @@ static bool radeon_msi_ok(struct radeon_device *rdev)
*/
if (rdev->family < CHIP_BONAIRE) {
dev_info(rdev->dev, "radeon: MSI limited to 32-bit\n");
- rdev->pdev->no_64bit_msi = 1;
+ rdev->pdev->msi_addr_mask = DMA_BIT_MASK(32);
}

/* force MSI on */
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_bus_pci.c b/drivers/net/ethernet/pensando/ionic/ionic_bus_pci.c
index 70d86c5f52fb..0671deae9a28 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_bus_pci.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_bus_pci.c
@@ -331,7 +331,7 @@ static int ionic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)

#ifdef CONFIG_PPC64
/* Ensure MSI/MSI-X interrupts lie within addressable physical memory */
- pdev->no_64bit_msi = 1;
+ pdev->msi_addr_mask = DMA_BIT_MASK(32);
#endif

err = ionic_setup_one(ionic);
diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
index 34d664139f48..48f5f03d1479 100644
--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -322,7 +322,7 @@ static int msi_verify_entries(struct pci_dev *dev)
{
struct msi_desc *entry;

- if (!dev->no_64bit_msi)
+ if (dev->msi_addr_mask == DMA_BIT_MASK(64))
return 0;

msi_for_each_desc(entry, &dev->dev, MSI_DESC_ALL) {
diff --git a/drivers/pci/msi/pcidev_msi.c b/drivers/pci/msi/pcidev_msi.c
index 5520aff53b56..0b0346813092 100644
--- a/drivers/pci/msi/pcidev_msi.c
+++ b/drivers/pci/msi/pcidev_msi.c
@@ -24,7 +24,7 @@ void pci_msi_init(struct pci_dev *dev)
}

if (!(ctrl & PCI_MSI_FLAGS_64BIT))
- dev->no_64bit_msi = 1;
+ dev->msi_addr_mask = DMA_BIT_MASK(32);
}

void pci_msix_init(struct pci_dev *dev)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 41183aed8f5d..a2bff57176a3 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2047,6 +2047,13 @@ int pci_setup_device(struct pci_dev *dev)
*/
dev->dma_mask = 0xffffffff;

+ /*
+ * Assume 64-bit addresses for MSI initially. Will be changed to 32-bit
+ * if MSI (rather than MSI-X) capability does not have
+ * PCI_MSI_FLAGS_64BIT. Can also be overridden by driver.
+ */
+ dev->msi_addr_mask = DMA_BIT_MASK(64);
+
dev_set_name(&dev->dev, "%04x:%02x:%02x.%d", pci_domain_nr(dev->bus),
dev->bus->number, PCI_SLOT(dev->devfn),
PCI_FUNC(dev->devfn));
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 864775651c6f..0fe32fef0331 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -377,6 +377,13 @@ struct pci_dev {
0xffffffff. You only need to change
this if your device has broken DMA
or supports 64-bit transfers. */
+ u64 msi_addr_mask; /* Mask of the bits of bus address for
+ MSI that this device implements.
+ Normally set based on device
+ capabilities. You only need to
+ change this if your device claims
+ to support 64-bit MSI but implements
+ fewer than 64 address bits. */

struct device_dma_parameters dma_parms;

@@ -441,7 +448,6 @@ struct pci_dev {

unsigned int is_busmaster:1; /* Is busmaster */
unsigned int no_msi:1; /* May not use MSI */
- unsigned int no_64bit_msi:1; /* May only use 32-bit MSIs */
unsigned int block_cfg_access:1; /* Config space access blocked */
unsigned int broken_parity_status:1; /* Generates false positive parity */
unsigned int irq_reroute_variant:2; /* Needs IRQ rerouting variant */
diff --git a/sound/hda/controllers/intel.c b/sound/hda/controllers/intel.c
index 1e8e3d61291a..c9542ebdf7e2 100644
--- a/sound/hda/controllers/intel.c
+++ b/sound/hda/controllers/intel.c
@@ -1905,7 +1905,7 @@ static int azx_first_init(struct azx *chip)

if (chip->msi && chip->driver_caps & AZX_DCAPS_NO_MSI64) {
dev_dbg(card->dev, "Disabling 64bit MSI\n");
- pci->no_64bit_msi = true;
+ pci->msi_addr_mask = DMA_BIT_MASK(32);
}

pci_set_master(pci);

--
2.52.0