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[RFC XEN PATCH v6 4/5] libxl: Use gsi instead of irq for mapping pirq
Jiqian.Chen at amd
Mar 27, 2024, 11:34 PM
Post #1 of 3 (19 views)
Permalink
In PVH dom0, it uses the linux local interrupt mechanism,
when it allocs irq for a gsi, it is dynamic, and follow
the principle of applying first, distributing first. And
the irq number is alloced from small to large, but the
applying gsi number is not, may gsi 38 comes before gsi
28, that causes the irq number is not equal with the gsi
number. And when passthrough a device, xl wants to use
gsi to map pirq, see pci_add_dm_done->xc_physdev_map_pirq,
but the gsi number is got from file
/sys/bus/pci/devices/<sbdf>/irq in current code, so it
will fail when mapping.

So, use real gsi number read from gsi sysfs.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

---
RFC: discussions ongoing on the Linux side where/how to expose the gsi

---
tools/libs/light/libxl_pci.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
index 96cb4da0794e..2cec83e0b734 100644
--- a/tools/libs/light/libxl_pci.c
+++ b/tools/libs/light/libxl_pci.c
@@ -1478,8 +1478,14 @@ static void pci_add_dm_done(libxl__egc *egc,
fclose(f);
if (!pci_supp_legacy_irq())
goto out_no_irq;
- sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
+ sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/gsi", pci->domain,
pci->bus, pci->dev, pci->func);
+ r = access(sysfs_path, F_OK);
+ if (r && errno == ENOENT) {
+ /* To compitable with old version of kernel, still need to use irq */
+ sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
+ pci->bus, pci->dev, pci->func);
+ }
f = fopen(sysfs_path, "r");
if (f == NULL) {
LOGED(ERROR, domainid, "Couldn't open %s", sysfs_path);
@@ -2229,9 +2235,15 @@ skip_bar:
if (!pci_supp_legacy_irq())
goto skip_legacy_irq;

- sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
+ sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/gsi", pci->domain,
pci->bus, pci->dev, pci->func);

+ rc = access(sysfs_path, F_OK);
+ if (rc && errno == ENOENT) {
+ /* To compitable with old version of kernel, still need to use irq */
+ sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
+ pci->bus, pci->dev, pci->func);
+ }
f = fopen(sysfs_path, "r");
if (f == NULL) {
LOGED(ERROR, domid, "Couldn't open %s", sysfs_path);
--
2.34.1
Re: [RFC XEN PATCH v6 4/5] libxl: Use gsi instead of irq for mapping pirq [ In reply to ]
anthony.perard at cloud
Mar 28, 2024, 10:32 AM
Post #2 of 3 (19 views)
Permalink
On Thu, Mar 28, 2024 at 02:34:01PM +0800, Jiqian Chen wrote:
> diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
> index 96cb4da0794e..2cec83e0b734 100644
> --- a/tools/libs/light/libxl_pci.c
> +++ b/tools/libs/light/libxl_pci.c
> @@ -1478,8 +1478,14 @@ static void pci_add_dm_done(libxl__egc *egc,
> fclose(f);
> if (!pci_supp_legacy_irq())
> goto out_no_irq;
> - sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/gsi", pci->domain,
> pci->bus, pci->dev, pci->func);
> + r = access(sysfs_path, F_OK);
> + if (r && errno == ENOENT) {
> + /* To compitable with old version of kernel, still need to use irq */

There's a typo, this would be "To be compatible ...". Also maybe
something like "Fallback to "/irq" for compatibility with old version of
the kernel." might sound better.

> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
> + pci->bus, pci->dev, pci->func);
> + }
> f = fopen(sysfs_path, "r");
> if (f == NULL) {
> LOGED(ERROR, domainid, "Couldn't open %s", sysfs_path);
> @@ -2229,9 +2235,15 @@ skip_bar:
> if (!pci_supp_legacy_irq())
> goto skip_legacy_irq;
>
> - sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/gsi", pci->domain,
> pci->bus, pci->dev, pci->func);
>
> + rc = access(sysfs_path, F_OK);

Please, don't use the variable `rc` here, this one is reserved for libxl
error/return code in libxl. Introduce `int r` instead.

> + if (rc && errno == ENOENT) {
> + /* To compitable with old version of kernel, still need to use irq */
> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
> + pci->bus, pci->dev, pci->func);
> + }
> f = fopen(sysfs_path, "r");
> if (f == NULL) {
> LOGED(ERROR, domid, "Couldn't open %s", sysfs_path);

With those two things fixed: Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

Thanks,

--
Anthony PERARD
Re: [RFC XEN PATCH v6 4/5] libxl: Use gsi instead of irq for mapping pirq [ In reply to ]
Jiqian.Chen at amd
Mar 28, 2024, 8:30 PM
Post #3 of 3 (19 views)
Permalink
On 2024/3/29 01:32, Anthony PERARD wrote:
> On Thu, Mar 28, 2024 at 02:34:01PM +0800, Jiqian Chen wrote:
>> diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
>> index 96cb4da0794e..2cec83e0b734 100644
>> --- a/tools/libs/light/libxl_pci.c
>> +++ b/tools/libs/light/libxl_pci.c
>> @@ -1478,8 +1478,14 @@ static void pci_add_dm_done(libxl__egc *egc,
>> fclose(f);
>> if (!pci_supp_legacy_irq())
>> goto out_no_irq;
>> - sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
>> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/gsi", pci->domain,
>> pci->bus, pci->dev, pci->func);
>> + r = access(sysfs_path, F_OK);
>> + if (r && errno == ENOENT) {
>> + /* To compitable with old version of kernel, still need to use irq */
>
> There's a typo, this would be "To be compatible ...". Also maybe
> something like "Fallback to "/irq" for compatibility with old version of
> the kernel." might sound better.
>
>> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
>> + pci->bus, pci->dev, pci->func);
>> + }
>> f = fopen(sysfs_path, "r");
>> if (f == NULL) {
>> LOGED(ERROR, domainid, "Couldn't open %s", sysfs_path);
>> @@ -2229,9 +2235,15 @@ skip_bar:
>> if (!pci_supp_legacy_irq())
>> goto skip_legacy_irq;
>>
>> - sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
>> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/gsi", pci->domain,
>> pci->bus, pci->dev, pci->func);
>>
>> + rc = access(sysfs_path, F_OK);
>
> Please, don't use the variable `rc` here, this one is reserved for libxl
> error/return code in libxl. Introduce `int r` instead.
>
>> + if (rc && errno == ENOENT) {
>> + /* To compitable with old version of kernel, still need to use irq */
>> + sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
>> + pci->bus, pci->dev, pci->func);
>> + }
>> f = fopen(sysfs_path, "r");
>> if (f == NULL) {
>> LOGED(ERROR, domid, "Couldn't open %s", sysfs_path);
>
> With those two things fixed: Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Thank you very much!
I will fix those two in next version.

>
> Thanks,
>

--
Best regards,
Jiqian Chen.

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