kernel/linux.git/drivers/tty/hvc, branch v6.1.87

hvc/xen: fix event channel handling for secondary consoles

2023-11-28T17:07:08+00:00

commit ef5dd8ec88ac11e8e353164407d55b73c988b369 upstream. The xencons_connect_backend() function allocates a local interdomain event channel with xenbus_alloc_evtchn(), then calls bind_interdomain_evtchn_to_irq_lateeoi() to bind to that port# on the *remote* domain. That doesn't work very well: (qemu) device_add xen-console,id=con1,chardev=pty0 [ 44.323872] xenconsole console-1: 2 xenbus_dev_probe on device/console/1 [ 44.323995] xenconsole: probe of console-1 failed with error -2 Fix it to use bind_evtchn_to_irq_lateeoi(), which does the right thing by just binding that *local* event channel to an irq. The backend will do the interdomain binding. This didn't affect the primary console because the setup for that is special — the toolstack allocates the guest event channel and the guest discovers it with HVMOP_get_param. Fixes: fe415186b43d ("xen/console: harden hvc_xen against event channel storms") Signed-off-by: David Woodhouse Reviewed-by: Juergen Gross Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20231020161529.355083-2-dwmw2@infradead.org Signed-off-by: Greg Kroah-Hartman

hvc/xen: fix error path in xen_hvc_init() to always register frontend driver

2023-11-28T17:07:08+00:00

commit 2704c9a5593f4a47620c12dad78838ca62b52f48 upstream. The xen_hvc_init() function should always register the frontend driver, even when there's no primary console — as there may be secondary consoles. (Qemu can always add secondary consoles, but only the toolstack can add the primary because it's special.) Signed-off-by: David Woodhouse Reviewed-by: Juergen Gross Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20231020161529.355083-3-dwmw2@infradead.org Signed-off-by: Greg Kroah-Hartman

hvc/xen: fix console unplug

2023-11-28T17:07:08+00:00

commit a30badfd7c13fc8763a9e10c5a12ba7f81515a55 upstream. On unplug of a Xen console, xencons_disconnect_backend() unconditionally calls free_irq() via unbind_from_irqhandler(), causing a warning of freeing an already-free IRQ: (qemu) device_del con1 [ 32.050919] ------------[ cut here ]------------ [ 32.050942] Trying to free already-free IRQ 33 [ 32.050990] WARNING: CPU: 0 PID: 51 at kernel/irq/manage.c:1895 __free_irq+0x1d4/0x330 It should be using evtchn_put() to tear down the event channel binding, and let the Linux IRQ side of it be handled by notifier_del_irq() through the HVC code. On which topic... xencons_disconnect_backend() should call hvc_remove() *first*, rather than tearing down the event channel and grant mapping while they are in use. And then the IRQ is guaranteed to be freed by the time it's torn down by evtchn_put(). Since evtchn_put() also closes the actual event channel, avoid calling xenbus_free_evtchn() except in the failure path where the IRQ was not successfully set up. However, calling hvc_remove() at the start of xencons_disconnect_backend() still isn't early enough. An unplug request is indicated by the backend setting its state to XenbusStateClosing, which triggers a notification to xencons_backend_changed(), which... does nothing except set its own frontend state directly to XenbusStateClosed without *actually* tearing down the HVC device or, you know, making sure it isn't actively in use. So the backend sees the guest frontend set its state to XenbusStateClosed and stops servicing the interrupt... and the guest spins for ever in the domU_write_console() function waiting for the ring to drain. Fix that one by calling hvc_remove() from xencons_backend_changed() before signalling to the backend that it's OK to proceed with the removal. Tested with 'dd if=/dev/zero of=/dev/hvc1' while telling Qemu to remove the console device. Signed-off-by: David Woodhouse Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20231020161529.355083-4-dwmw2@infradead.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman

hvc/xen: prevent concurrent accesses to the shared ring

2023-03-30T10:49:09+00:00

[ Upstream commit 6214894f49a967c749ee6c07cb00f9cede748df4 ] The hvc machinery registers both a console and a tty device based on the hv ops provided by the specific implementation. Those two interfaces however have different locks, and there's no single locks that's shared between the tty and the console implementations, hence the driver needs to protect itself against concurrent accesses. Otherwise concurrent calls using the split interfaces are likely to corrupt the ring indexes, leaving the console unusable. Introduce a lock to xencons_info to serialize accesses to the shared ring. This is only required when using the shared memory console, concurrent accesses to the hypercall based console implementation are not an issue. Note the conditional logic in domU_read_console() is slightly modified so the notify_daemon() call can be done outside of the locked region: it's an hypercall and there's no need for it to be done with the lock held. Fixes: b536b4b96230 ('xen: use the hvc console infrastructure for Xen console') Signed-off-by: Roger Pau Monné Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/20221130150919.13935-1-roger.pau@citrix.com Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin

hvc/xen: lock console list traversal

2023-01-18T10:58:26+00:00

[ Upstream commit c0dccad87cf68fc6012aec7567e354353097ec1a ] The currently lockless access to the xen console list in vtermno_to_xencons() is incorrect, as additions and removals from the list can happen anytime, and as such the traversal of the list to get the private console data for a given termno needs to happen with the lock held. Note users that modify the list already do so with the lock taken. Adjust current lock takers to use the _irq{save,restore} helpers, since the context in which vtermno_to_xencons() is called can have interrupts disabled. Use the _irq{save,restore} set of helpers to switch the current callers to disable interrupts in the locked region. I haven't checked if existing users could instead use the _irq variant, as I think it's safer to use _irq{save,restore} upfront. While there switch from using list_for_each_entry_safe to list_for_each_entry: the current entry cursor won't be removed as part of the code in the loop body, so using the _safe variant is pointless. Fixes: 02e19f9c7cac ('hvc_xen: implement multiconsole support') Signed-off-by: Roger Pau Monné Reviewed-by: Stefano Stabellini Link: https://lore.kernel.org/r/20221130163611.14686-1-roger.pau@citrix.com Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin

tty: hvc: remove HVC_IUCV_MAGIC

2022-09-22T14:12:34+00:00

According to Greg, in the context of magic numbers as defined in magic-number.rst, "the tty layer should not need this and I'll gladly take patches" This stretches that definition slightly, since it multiplexes it with the terminal number as a constant offset, but is equivalent Acked-by: Jiri Slaby Signed-off-by: Ahelenia Ziemiańska Ref: https://lore.kernel.org/linux-doc/YyMlovoskUcHLEb7@kroah.com/ Link: https://lore.kernel.org/r/8c8a2c9dfc1bfbe6ef3f3237368e483865fc1c29.1663288066.git.nabijaczleweli@nabijaczleweli.xyz Signed-off-by: Greg Kroah-Hartman

termios: start unifying non-UAPI parts of asm/termios.h

2022-09-09T08:44:34+00:00

* new header (linut/termios_internal.h), pulled by the users of those suckers * defaults for INIT_C_CC and externs for conversion helpers moved over there * remove termios-base.h (empty now) Signed-off-by: Al Viro Link: https://lore.kernel.org/r/YxDmptU7dNGZ+/Hn@ZenIV Signed-off-by: Greg Kroah-Hartman

tty: move from strlcpy with unused retval to strscpy

2022-08-30T12:21:59+00:00

Follow the advice of the below link and prefer 'strscpy' in this subsystem. Conversion is 1:1 because the return value is not used. Generated by a coccinelle script. Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/ Reviewed-by: Jiri Slaby Signed-off-by: Wolfram Sang Link: https://lore.kernel.org/r/20220818210113.7469-1-wsa+renesas@sang-engineering.com Signed-off-by: Greg Kroah-Hartman

Merge tag 'for-linus-5.19-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

2022-06-04T20:42:53+00:00

Pull more xen updates from Juergen Gross: "Two cleanup patches for Xen related code and (more important) an update of MAINTAINERS for Xen, as Boris Ostrovsky decided to step down" * tag 'for-linus-5.19-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: xen: replace xen_remap() with memremap() MAINTAINERS: Update Xen maintainership xen: switch gnttab_end_foreign_access() to take a struct page pointer

xen: replace xen_remap() with memremap()

2022-06-01T05:24:17+00:00

xen_remap() is used to establish mappings for frames not under direct control of the kernel: for Xenstore and console ring pages, and for grant pages of non-PV guests. Today xen_remap() is defined to use ioremap() on x86 (doing uncached mappings), and ioremap_cache() on Arm (doing cached mappings). Uncached mappings for those use cases are bad for performance, so they should be avoided if possible. As all use cases of xen_remap() don't require uncached mappings (the mapped area is always physical RAM), a mapping using the standard WB cache mode is fine. As sparse is flagging some of the xen_remap() use cases to be not appropriate for iomem(), as the result is not annotated with the __iomem modifier, eliminate xen_remap() completely and replace all use cases with memremap() specifying the MEMREMAP_WB caching mode. xen_unmap() can be replaced with memunmap(). Reported-by: kernel test robot Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Acked-by: Stefano Stabellini Link: https://lore.kernel.org/r/20220530082634.6339-1-jgross@suse.com Signed-off-by: Juergen Gross