Reinette!
On Fri, Dec 02 2022 at 09:55, Reinette Chatre wrote:
> On 11/11/2022 5:59 AM, Thomas Gleixner wrote:
>> The necessary iobase is stored in the irqdomain and the PASID which is
>> required for operation is handed in via msi_dev_cookie in the allocation
>> function.
>
> The use of PASID is optional for dedicated workqueues. Could this be
> supported to let the irqchip support all scenarios?
Sure. I wrote this thing mostly out of thin air based on some ancient
PoC code. :)
> Since the cookie is always provided I was wondering if an invalid
> PASID can be used to let the driver disable PASID? Please see the
> delta snippet below in which I primarily made such a change, but added
> a few more changes for consideration.
Let me check.
> With the first change I am able to test IMS on the host using devmsi-v2-part3
> of the development branch. I did try to update to the most recent development
> to confirm all is well but version devmsi-v3.1-part3 behaves differently
> in that pci_ims_alloc_irq() returns successfully but the returned
> virq is 0. This triggers a problem when request_threaded_irq() runs and
> reports:
> genirq: Flags mismatch irq 0. 00000000 (idxd-portal) vs. 00015a00 (timer)
Bah. Let me figure out what I fat-fingered there.
> @@ -33,6 +34,8 @@ struct ims_slot {
> #define CTRL_PASID_ENABLE BIT(3)
> /* Position of PASID.LSB in the control word */
> #define CTRL_PASID_SHIFT 12
> +/* Valid PASID is 20 bits */
> +#define CTRL_PASID_VALID GENMASK(19, 0)
>
> static inline void iowrite32_and_flush(u32 value, void __iomem *addr)
> {
> @@ -93,12 +96,17 @@ static void idxd_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> /* Mask the interrupt for paranoia sake */
> iowrite32_and_flush(CTRL_VECTOR_MASKBIT, &slot->ctrl);
>
> - /*
> - * The caller provided PASID. Shift it to the proper position
> - * and set the PASID enable bit.
> - */
> - desc->data.icookie.value <<= CTRL_PASID_SHIFT;
> - desc->data.icookie.value |= CTRL_PASID_ENABLE;
> + if (pasid_valid((ioasid_t)desc->data.icookie.value)) {
> + /*
> + * The caller provided PASID. Shift it to the proper position
> + * and set the PASID enable bit.
> + */
> + desc->data.icookie.value &= CTRL_PASID_VALID;
> + desc->data.icookie.value <<= CTRL_PASID_SHIFT;
> + desc->data.icookie.value |= CTRL_PASID_ENABLE;
> + } else {
> + desc->data.icookie.value = 0;
> + }
Looks about right. But that needs some sanity measures at the call sites
so that we don't end up with an invalid PASID in cases where a valid
PASID is truly required.
Thanks,
tglx
