Revision 706a1ea65e6faaf853427a0e931f59d604dd45e3 authored by Linus Torvalds on 23 August 2018, 21:55:01 UTC, committed by Linus Torvalds on 23 August 2018, 21:55:01 UTC
Merge fixes for missing TLB shootdowns. This fixes a couple of cases that involved us possibly freeing page table structures before the required TLB shootdown had been done. There are a few cleanup patches to make the code easier to follow, and to avoid some of the more problematic cases entirely when not necessary. To make this easier for backports, it undoes the recent lazy TLB patches, because the cleanups and fixes are more important, and Rik is ok with re-doing them later when things have calmed down. The missing TLB flush was only delayed, and the wrong ordering only happened under memory pressure (and in theory under a couple of other fairly theoretical situations), so this may have been all very unlikely to have hit people in practice. But getting the TLB shootdown wrong is _so_ hard to debug and see that I consider this a crticial fix. Many thanks to Jann Horn for having debugged this. * tlb-fixes: x86/mm: Only use tlb_remove_table() for paravirt mm: mmu_notifier fix for tlb_end_vma mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE_FREE mm/tlb: Remove tlb_remove_table() non-concurrent condition mm: move tlb_table_flush to tlb_flush_mmu_free x86/mm/tlb: Revert the recent lazy TLB patches
mailbox.txt
============================
The Common Mailbox Framework
============================
:Author: Jassi Brar <jaswinder.singh@linaro.org>
This document aims to help developers write client and controller
drivers for the API. But before we start, let us note that the
client (especially) and controller drivers are likely going to be
very platform specific because the remote firmware is likely to be
proprietary and implement non-standard protocol. So even if two
platforms employ, say, PL320 controller, the client drivers can't
be shared across them. Even the PL320 driver might need to accommodate
some platform specific quirks. So the API is meant mainly to avoid
similar copies of code written for each platform. Having said that,
nothing prevents the remote f/w to also be Linux based and use the
same api there. However none of that helps us locally because we only
ever deal at client's protocol level.
Some of the choices made during implementation are the result of this
peculiarity of this "common" framework.
Controller Driver (See include/linux/mailbox_controller.h)
==========================================================
Allocate mbox_controller and the array of mbox_chan.
Populate mbox_chan_ops, except peek_data() all are mandatory.
The controller driver might know a message has been consumed
by the remote by getting an IRQ or polling some hardware flag
or it can never know (the client knows by way of the protocol).
The method in order of preference is IRQ -> Poll -> None, which
the controller driver should set via 'txdone_irq' or 'txdone_poll'
or neither.
Client Driver (See include/linux/mailbox_client.h)
==================================================
The client might want to operate in blocking mode (synchronously
send a message through before returning) or non-blocking/async mode (submit
a message and a callback function to the API and return immediately).
::
struct demo_client {
struct mbox_client cl;
struct mbox_chan *mbox;
struct completion c;
bool async;
/* ... */
};
/*
* This is the handler for data received from remote. The behaviour is purely
* dependent upon the protocol. This is just an example.
*/
static void message_from_remote(struct mbox_client *cl, void *mssg)
{
struct demo_client *dc = container_of(cl, struct demo_client, cl);
if (dc->async) {
if (is_an_ack(mssg)) {
/* An ACK to our last sample sent */
return; /* Or do something else here */
} else { /* A new message from remote */
queue_req(mssg);
}
} else {
/* Remote f/w sends only ACK packets on this channel */
return;
}
}
static void sample_sent(struct mbox_client *cl, void *mssg, int r)
{
struct demo_client *dc = container_of(cl, struct demo_client, cl);
complete(&dc->c);
}
static void client_demo(struct platform_device *pdev)
{
struct demo_client *dc_sync, *dc_async;
/* The controller already knows async_pkt and sync_pkt */
struct async_pkt ap;
struct sync_pkt sp;
dc_sync = kzalloc(sizeof(*dc_sync), GFP_KERNEL);
dc_async = kzalloc(sizeof(*dc_async), GFP_KERNEL);
/* Populate non-blocking mode client */
dc_async->cl.dev = &pdev->dev;
dc_async->cl.rx_callback = message_from_remote;
dc_async->cl.tx_done = sample_sent;
dc_async->cl.tx_block = false;
dc_async->cl.tx_tout = 0; /* doesn't matter here */
dc_async->cl.knows_txdone = false; /* depending upon protocol */
dc_async->async = true;
init_completion(&dc_async->c);
/* Populate blocking mode client */
dc_sync->cl.dev = &pdev->dev;
dc_sync->cl.rx_callback = message_from_remote;
dc_sync->cl.tx_done = NULL; /* operate in blocking mode */
dc_sync->cl.tx_block = true;
dc_sync->cl.tx_tout = 500; /* by half a second */
dc_sync->cl.knows_txdone = false; /* depending upon protocol */
dc_sync->async = false;
/* ASync mailbox is listed second in 'mboxes' property */
dc_async->mbox = mbox_request_channel(&dc_async->cl, 1);
/* Populate data packet */
/* ap.xxx = 123; etc */
/* Send async message to remote */
mbox_send_message(dc_async->mbox, &ap);
/* Sync mailbox is listed first in 'mboxes' property */
dc_sync->mbox = mbox_request_channel(&dc_sync->cl, 0);
/* Populate data packet */
/* sp.abc = 123; etc */
/* Send message to remote in blocking mode */
mbox_send_message(dc_sync->mbox, &sp);
/* At this point 'sp' has been sent */
/* Now wait for async chan to be done */
wait_for_completion(&dc_async->c);
}
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