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Message-ID: <20251231170150.GA160311@bhelgaas>
Date: Wed, 31 Dec 2025 11:01:50 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
linux-pci@...r.kernel.org, Len Brown <lenb@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
"Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] ACPI: PCI: IRQ: Handle INTx GSIs as u32 values not int
On Wed, Dec 31, 2025 at 10:26:15AM +0100, Lorenzo Pieralisi wrote:
> In ACPI Global System Interrupts (GSIs) are described using a 32-bit
> value.
>
> ACPI/PCI legacy interrupts (INTx) parsing code treats GSIs as 'int', which
> poses issues if the GSI interrupt value is a 32-bit value with the MSB set
> (as required in some interrupt configurations - eg ARM64 GICv5 systems).
>
> Fix ACPI/PCI legacy INTx parsing by converting variables representing
> GSIs from 'int' to 'u32' bringing the code in line with the ACPI
> specification.
Looks good to me. Is there any symptom of what the issue looks like
that could be mentioned here? Might also be useful in the subject,
which currently describes the C code without really saying why we want
to do this.
Reviewed-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@...nel.org>
> Cc: Len Brown <lenb@...nel.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> ---
> drivers/acpi/pci_irq.c | 19 ++++++++++--------
> drivers/acpi/pci_link.c | 39 ++++++++++++++++++++++++-------------
> drivers/xen/acpi.c | 13 +++++++------
> include/acpi/acpi_drivers.h | 2 +-
> 4 files changed, 44 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index ad81aa03fe2f..c416942ff3e2 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -188,7 +188,7 @@ static int acpi_pci_irq_check_entry(acpi_handle handle, struct pci_dev *dev,
> * the IRQ value, which is hardwired to specific interrupt inputs on
> * the interrupt controller.
> */
> - pr_debug("%04x:%02x:%02x[%c] -> %s[%d]\n",
> + pr_debug("%04x:%02x:%02x[%c] -> %s[%u]\n",
> entry->id.segment, entry->id.bus, entry->id.device,
> pin_name(entry->pin), prt->source, entry->index);
>
> @@ -384,7 +384,7 @@ static inline bool acpi_pci_irq_valid(struct pci_dev *dev, u8 pin)
> int acpi_pci_irq_enable(struct pci_dev *dev)
> {
> struct acpi_prt_entry *entry;
> - int gsi;
> + u32 gsi;
> u8 pin;
> int triggering = ACPI_LEVEL_SENSITIVE;
> /*
> @@ -422,18 +422,21 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
> return 0;
> }
>
> + rc = -ENODEV;
> +
> if (entry) {
> if (entry->link)
> - gsi = acpi_pci_link_allocate_irq(entry->link,
> + rc = acpi_pci_link_allocate_irq(entry->link,
> entry->index,
> &triggering, &polarity,
> - &link);
> - else
> + &link, &gsi);
> + else {
> gsi = entry->index;
> - } else
> - gsi = -1;
> + rc = 0;
> + }
> + }
>
> - if (gsi < 0) {
> + if (rc < 0) {
> /*
> * No IRQ known to the ACPI subsystem - maybe the BIOS /
> * driver reported one, then use it. Exit in any case.
> diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
> index bed7dc85612e..b91b039a3d20 100644
> --- a/drivers/acpi/pci_link.c
> +++ b/drivers/acpi/pci_link.c
> @@ -448,7 +448,7 @@ static int acpi_isa_irq_penalty[ACPI_MAX_ISA_IRQS] = {
> /* >IRQ15 */
> };
>
> -static int acpi_irq_pci_sharing_penalty(int irq)
> +static int acpi_irq_pci_sharing_penalty(u32 irq)
> {
> struct acpi_pci_link *link;
> int penalty = 0;
> @@ -474,7 +474,7 @@ static int acpi_irq_pci_sharing_penalty(int irq)
> return penalty;
> }
>
> -static int acpi_irq_get_penalty(int irq)
> +static int acpi_irq_get_penalty(u32 irq)
> {
> int penalty = 0;
>
> @@ -528,7 +528,7 @@ static int acpi_irq_balance = -1; /* 0: static, 1: balance */
> static int acpi_pci_link_allocate(struct acpi_pci_link *link)
> {
> acpi_handle handle = link->device->handle;
> - int irq;
> + u32 irq;
> int i;
>
> if (link->irq.initialized) {
> @@ -598,44 +598,53 @@ static int acpi_pci_link_allocate(struct acpi_pci_link *link)
> return 0;
> }
>
> -/*
> - * acpi_pci_link_allocate_irq
> - * success: return IRQ >= 0
> - * failure: return -1
> +/**
> + * acpi_pci_link_allocate_irq(): Retrieve a link device GSI
> + *
> + * @handle: Handle for the link device
> + * @index: GSI index
> + * @triggering: pointer to store the GSI trigger
> + * @polarity: pointer to store GSI polarity
> + * @name: pointer to store link device name
> + * @gsi: pointer to store GSI number
> + *
> + * Returns:
> + * 0 on success with @triggering, @polarity, @name, @gsi initialized.
> + * -ENODEV on failure
> */
> int acpi_pci_link_allocate_irq(acpi_handle handle, int index, int *triggering,
> - int *polarity, char **name)
> + int *polarity, char **name, u32 *gsi)
> {
> struct acpi_device *device = acpi_fetch_acpi_dev(handle);
> struct acpi_pci_link *link;
>
> if (!device) {
> acpi_handle_err(handle, "Invalid link device\n");
> - return -1;
> + return -ENODEV;
> }
>
> link = acpi_driver_data(device);
> if (!link) {
> acpi_handle_err(handle, "Invalid link context\n");
> - return -1;
> + return -ENODEV;
> }
>
> /* TBD: Support multiple index (IRQ) entries per Link Device */
> if (index) {
> acpi_handle_err(handle, "Invalid index %d\n", index);
> - return -1;
> + return -ENODEV;
> }
>
> mutex_lock(&acpi_link_lock);
> if (acpi_pci_link_allocate(link)) {
> mutex_unlock(&acpi_link_lock);
> - return -1;
> + return -ENODEV;
> }
>
> if (!link->irq.active) {
> mutex_unlock(&acpi_link_lock);
> acpi_handle_err(handle, "Link active IRQ is 0!\n");
> - return -1;
> + return -ENODEV;
> }
> link->refcnt++;
> mutex_unlock(&acpi_link_lock);
> @@ -647,7 +656,9 @@ int acpi_pci_link_allocate_irq(acpi_handle handle, int index, int *triggering,
> if (name)
> *name = acpi_device_bid(link->device);
> acpi_handle_debug(handle, "Link is referenced\n");
> - return link->irq.active;
> + *gsi = link->irq.active;
> +
> + return 0;
> }
>
> /*
> diff --git a/drivers/xen/acpi.c b/drivers/xen/acpi.c
> index d2ee605c5ca1..eab28cfe9939 100644
> --- a/drivers/xen/acpi.c
> +++ b/drivers/xen/acpi.c
> @@ -89,11 +89,11 @@ int xen_acpi_get_gsi_info(struct pci_dev *dev,
> int *trigger_out,
> int *polarity_out)
> {
> - int gsi;
> + u32 gsi;
> u8 pin;
> struct acpi_prt_entry *entry;
> int trigger = ACPI_LEVEL_SENSITIVE;
> - int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ?
> + int ret, polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ?
> ACPI_ACTIVE_HIGH : ACPI_ACTIVE_LOW;
>
> if (!dev || !gsi_out || !trigger_out || !polarity_out)
> @@ -105,17 +105,18 @@ int xen_acpi_get_gsi_info(struct pci_dev *dev,
>
> entry = acpi_pci_irq_lookup(dev, pin);
> if (entry) {
> + ret = 0;
> if (entry->link)
> - gsi = acpi_pci_link_allocate_irq(entry->link,
> + ret = acpi_pci_link_allocate_irq(entry->link,
> entry->index,
> &trigger, &polarity,
> - NULL);
> + NULL, &gsi);
> else
> gsi = entry->index;
> } else
> - gsi = -1;
> + ret = -ENODEV;
>
> - if (gsi < 0)
> + if (ret < 0)
> return -EINVAL;
>
> *gsi_out = gsi;
> diff --git a/include/acpi/acpi_drivers.h b/include/acpi/acpi_drivers.h
> index b14d165632e7..402b97d12138 100644
> --- a/include/acpi/acpi_drivers.h
> +++ b/include/acpi/acpi_drivers.h
> @@ -51,7 +51,7 @@
>
> int acpi_irq_penalty_init(void);
> int acpi_pci_link_allocate_irq(acpi_handle handle, int index, int *triggering,
> - int *polarity, char **name);
> + int *polarity, char **name, u32 *gsi);
> int acpi_pci_link_free_irq(acpi_handle handle);
>
> /* ACPI PCI Device Binding */
> --
> 2.50.1
>
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