From: Grygorii Strashko <[email protected]> When 2 or more domains are created and: - one is hwdom with "hvc0" (console_io) console - other DomUs with vpl011 or "hvc0" (console_io) console console output from hwdom may mix with output from other domains.
Example: [ 2.288816] Key type id_legacy registered [ 2.291894] n(XEN) DOM1: [ 1.016950] DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations fs4filelayout_init: NFSv4 File Layout Driver Registering... (XEN) DOM1: [ 1.018846] audit: initializing netlink subsys (disabled) This happens because for hwdom the console output is produced by domain and handled by Xen as stream of chars, which can be interrupted when hwdom is scheduled out and so, cause console output mix. The Xen consoleio code trying to mimic serial HW behavior for hwdom unconditionally by sending available data to serial HW on arrival. Xen consoleio code does not account for Xen console input focus, comparing to emulated serial hw, like vpl011, which does the same for domain with active Xen console input focus only. Switching console input focus to Xen improves situation, but not enough. This patch changes consoleio code to account for domain with active Xen console input focus - console output will be sent directly to serial HW only if domain has active Xen console input focus. For other domains - console output will be buffered and sync on per-line basis. Example output: (d2) [ 4.263417] Key type id_legacy registered (XEN) DOM1: [ 4.658080] Advanced Linux Sound Architecture Driver Initialized. (d2) [ 4.277824] nfs4filelayout_init: NFSv4 File Layout Driver Registering... Signed-off-by: Grygorii Strashko <[email protected]> --- This causes random multi-domain tests failures due to inter-domain console mixing which breaks console parsing checks. xen/drivers/char/console.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c index a99605103552..391cefc1a7c6 100644 --- a/xen/drivers/char/console.c +++ b/xen/drivers/char/console.c @@ -733,6 +733,8 @@ static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, while ( count > 0 ) { + struct domain *input; + if ( kcount && hypercall_preempt_check() ) return hypercall_create_continuation( __HYPERVISOR_console_io, "iih", @@ -742,7 +744,9 @@ static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, if ( copy_from_guest(kbuf, buffer, kcount) ) return -EFAULT; - if ( is_hardware_domain(cd) ) + input = console_get_domain(); + + if ( cd == input ) { /* Use direct console output as it could be interactive */ nrspin_lock_irq(&console_lock); @@ -783,6 +787,8 @@ static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, spin_unlock(&cons->lock); } + console_put_domain(input); + guest_handle_add_offset(buffer, kcount); count -= kcount; } -- 2.34.1
