Re: [PATCH v5 13/17] powerpc/pseries/vas: Setup IRQ and fault handling

Nicholas Piggin
2021-06-16T09:40:45Z

Excerpts from Haren Myneni's message of June 15, 2021 7:01 pm:
> On Mon, 2021-06-14 at 13:07 +1000, Nicholas Piggin wrote:
>> Excerpts from Haren Myneni's message of June 13, 2021 9:02 pm:
>> > NX generates an interrupt when sees a fault on the user space
>> > buffer and the hypervisor forwards that interrupt to OS. Then
>> > the kernel handles the interrupt by issuing H_GET_NX_FAULT hcall
>> > to retrieve the fault CRB information.
>> >
>> > This patch also adds changes to setup and free IRQ per each
>> > window and also handles the fault by updating the CSB.
>> >
>> > Signed-off-by: Haren Myneni <haren@linux.ibm.com>
>> > ---
>> > arch/powerpc/platforms/pseries/vas.c | 108
>> > +++++++++++++++++++++++++++
>> > 1 file changed, 108 insertions(+)
>> >
>> > diff --git a/arch/powerpc/platforms/pseries/vas.c
>> > b/arch/powerpc/platforms/pseries/vas.c
>> > index fe375f7a7029..55185bdd3776 100644
>> > --- a/arch/powerpc/platforms/pseries/vas.c
>> > +++ b/arch/powerpc/platforms/pseries/vas.c
>> > @@ -11,6 +11,7 @@
>> > #include <linux/types.h>
>> > #include <linux/delay.h>
>> > #include <linux/slab.h>
>> > +#include <linux/interrupt.h>
>> > #include <asm/machdep.h>
>> > #include <asm/hvcall.h>
>> > #include <asm/plpar_wrappers.h>
>> > @@ -190,6 +191,58 @@ int h_query_vas_capabilities(const u64 hcall,
>> > u8 query_type, u64 result)
>> > }
>> > EXPORT_SYMBOL_GPL(h_query_vas_capabilities);
>> >
>> > +/*
>> > + * hcall to get fault CRB from pHyp.
>> > + */
>> > +static int h_get_nx_fault(u32 winid, u64 buffer)
>> > +{
>> > + long rc;
>> > +
>> > + rc = plpar_hcall_norets(H_GET_NX_FAULT, winid, buffer);
>> > +
>> > + switch (rc) {
>> > + case H_SUCCESS:
>> > + return 0;
>> > + case H_PARAMETER:
>> > + pr_err("HCALL(%x): Invalid window ID %u\n",
>> > H_GET_NX_FAULT,
>> > + winid);
>> > + return -EINVAL;
>> > + case H_PRIVILEGE:
>> > + pr_err("HCALL(%x): Window(%u): Invalid fault buffer
>> > 0x%llx\n",
>> > + H_GET_NX_FAULT, winid, buffer);
>> > + return -EACCES;
>> > + default:
>> > + pr_err("HCALL(%x): Failed with error %ld for
>> > window(%u)\n",
>> > + H_GET_NX_FAULT, rc, winid);
>> > + return -EIO;
>>
>> 3 error messages have 3 different formats for window ID.
>>
>> I agree with Michael you could just have one error message that
>> reports
>> the return value. Also "H_GET_NX_FAULT: " would be nicer than
>> "HCALL(380): "
>
> yes, Added just one printk for all error codes except for errors which
> depend on arguments to HCALL (Ex: WinID).
>
> Sure, I will add just one error message and print all arguments passed
> to HCALL.
>
> pr_err("H_GET_NX_FAULT: window(%u), fault buffer(0x%llx) Failed with
> error %ld\n", rc, winid, buffer);

Thanks.

>>
>> Check how some other hcall failures are reported, "hcall failed:
>> H_CALL_NAME" seems to have a few takers.
>>
>> > + }
>> > +}
>> > +
>> > +/*
>> > + * Handle the fault interrupt.
>> > + * When the fault interrupt is received for each window, query
>> > pHyp to get
>> > + * the fault CRB on the specific fault. Then process the CRB by
>> > updating
>> > + * CSB or send signal if the user space CSB is invalid.
>> > + * Note: pHyp forwards an interrupt for each fault request. So one
>> > fault
>> > + * CRB to process for each H_GET_NX_FAULT HCALL.
>> > + */
>> > +irqreturn_t pseries_vas_fault_thread_fn(int irq, void *data)
>> > +{
>> > + struct pseries_vas_window *txwin = data;
>> > + struct coprocessor_request_block crb;
>> > + struct vas_user_win_ref *tsk_ref;
>> > + int rc;
>> > +
>> > + rc = h_get_nx_fault(txwin->vas_win.winid,
>> > (u64)virt_to_phys(&crb));
>> > + if (!rc) {
>> > + tsk_ref = &txwin->vas_win.task_ref;
>> > + vas_dump_crb(&crb);
>> > + vas_update_csb(&crb, tsk_ref);
>> > + }
>> > +
>> > + return IRQ_HANDLED;
>> > +}
>> > +
>> > /*
>> > * Allocate window and setup IRQ mapping.
>> > */
>> > @@ -201,10 +254,51 @@ static int allocate_setup_window(struct
>> > pseries_vas_window *txwin,
>> > rc = h_allocate_vas_window(txwin, domain, wintype,
>> > DEF_WIN_CREDS);
>> > if (rc)
>> > return rc;
>> > + /*
>> > + * On powerVM, pHyp setup and forwards the fault interrupt per
>>
>> The hypervisor forwards the fault interrupt per-window...
>>
>> > + * window. So the IRQ setup and fault handling will be done for
>> > + * each open window separately.
>> > + */
>> > + txwin->fault_virq = irq_create_mapping(NULL, txwin->fault_irq);
>> > + if (!txwin->fault_virq) {
>> > + pr_err("Failed irq mapping %d\n", txwin->fault_irq);
>> > + rc = -EINVAL;
>> > + goto out_win;
>> > + }
>> > +
>> > + txwin->name = kasprintf(GFP_KERNEL, "vas-win-%d",
>> > + txwin->vas_win.winid);
>> > + if (!txwin->name) {
>> > + rc = -ENOMEM;
>> > + goto out_irq;
>> > + }
>> > +
>> > + rc = request_threaded_irq(txwin->fault_virq, NULL,
>> > + pseries_vas_fault_thread_fn,
>> > IRQF_ONESHOT,
>> > + txwin->name, txwin);
>> > + if (rc) {
>> > + pr_err("VAS-Window[%d]: Request IRQ(%u) failed with
>> > %d\n",
>> > + txwin->vas_win.winid, txwin->fault_virq, rc);
>> > + goto out_free;
>> > + }
>> >
>> > txwin->vas_win.wcreds_max = DEF_WIN_CREDS;
>> >
>> > return 0;
>> > +out_free:
>> > + kfree(txwin->name);
>> > +out_irq:
>> > + irq_dispose_mapping(txwin->fault_virq);
>> > +out_win:
>> > + h_deallocate_vas_window(txwin->vas_win.winid);
>> > + return rc;
>> > +}
>> > +
>> > +static inline void free_irq_setup(struct pseries_vas_window
>> > *txwin)
>> > +{
>> > + free_irq(txwin->fault_virq, txwin);
>> > + irq_dispose_mapping(txwin->fault_virq);
>> > + kfree(txwin->name);
>>
>> Nit, but this freeing is in a different order than the error handling
>> in
>> the function does. I'd just keep it the same unless there is a reason
>> to
>> be different, in which case it could use a comment.
>
> shouldn't matter, I can change it to:
> static inline void free_irq_setup(struct pseries_vas_window *txwin)
> {
> free_irq(txwin->fault_virq, txwin);
> kfree(txwin->name);
> irq_dispose_mapping(txwin->fault_virq);
> }

Okay, it wasn't a big deal I was just wondering. Given the changes,

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Thanks,
Nick