Re: [PATCH v4 12/16] powerpc/pseries/vas: Setup IRQ and fault handling
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-06-03 05:49:31
Also in:
linux-crypto
Excerpts from Haren Myneni's message of May 21, 2021 7:39 pm:
quoted hunk ↗ jump to hunk
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 | 111 +++++++++++++++++++++++++++ 1 file changed, 111 insertions(+)diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c index ef0c455f6e93..31dc17573f50 100644 --- a/arch/powerpc/platforms/pseries/vas.c +++ b/arch/powerpc/platforms/pseries/vas.c@@ -224,6 +224,62 @@ int plpar_vas_query_capabilities(const u64 hcall, u8 query_type, } EXPORT_SYMBOL_GPL(plpar_vas_query_capabilities); +/* + * HCALL to get fault CRB from pHyp. + */ +static int plpar_get_nx_fault(u32 winid, u64 buffer) +{ + int64_t 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_STATE: + pr_err("HCALL(%x): No outstanding faults for 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): Unexpected error %lld for window(%u)\n", + H_GET_NX_FAULT, rc, winid); + return -EIO; + } +}
Out of curiosity, you get one of these errors and it just drops the interrupt on the floor. Then what happens, I assume everything stops. Should it put some error in the csb, or signal the process or something? Or is there nothing very sane that can be done?
+
+/*
+ * 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 vas_window *txwin = data;
+ struct coprocessor_request_block crb;
+ struct vas_user_win_ref *tsk_ref;
+ int rc;
+
+ rc = plpar_get_nx_fault(txwin->winid, (u64)virt_to_phys(&crb));
+ if (!rc) {
+ tsk_ref = &txwin->task_ref;
+ vas_dump_crb(&crb);This (and existing powernv vas code) is printk()ing a lot of lines per fault. This should be pretty normal operation I think? It should avoid filling the kernel logs, if so. Particularly if it can be triggered by userspace. I know it's existing code, so could be fixed separately from the series.
+ vas_update_csb(&crb, tsk_ref);
+ }
+ + return IRQ_HANDLED; +} +