From 7825cf10e31c64ece3cac66fb01a742f1094da51 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 20 Oct 2009 15:28:21 +0900 Subject: [PATCH 1/2] xen/hvc: make sure console output is always emitted, with explicit polling We never want to rely on the hvc workqueue to emit output, because the most interesting output is when the kernel is broken. This will improve oops/crash/console message for better debugging. Instead, we force-poll until all output is emitted. Signed-off-by: Jeremy Fitzhardinge Cc: Stable Kernel --- drivers/char/hvc_xen.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/drivers/char/hvc_xen.c b/drivers/char/hvc_xen.c index eba999f8598..a6ee32b599a 100644 --- a/drivers/char/hvc_xen.c +++ b/drivers/char/hvc_xen.c @@ -55,7 +55,7 @@ static inline void notify_daemon(void) notify_remote_via_evtchn(xen_start_info->console.domU.evtchn); } -static int write_console(uint32_t vtermno, const char *data, int len) +static int __write_console(const char *data, int len) { struct xencons_interface *intf = xencons_interface(); XENCONS_RING_IDX cons, prod; @@ -76,6 +76,29 @@ static int write_console(uint32_t vtermno, const char *data, int len) return sent; } +static int write_console(uint32_t vtermno, const char *data, int len) +{ + int ret = len; + + /* + * Make sure the whole buffer is emitted, polling if + * necessary. We don't ever want to rely on the hvc daemon + * because the most interesting console output is when the + * kernel is crippled. + */ + while (len) { + int sent = __write_console(data, len); + + data += sent; + len -= sent; + + if (unlikely(len)) + HYPERVISOR_sched_op(SCHEDOP_yield, NULL); + } + + return ret; +} + static int read_console(uint32_t vtermno, char *buf, int len) { struct xencons_interface *intf = xencons_interface(); From 82d6469916c6fcfa345636a49004c9d1753905d1 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Thu, 22 Oct 2009 16:41:15 -0700 Subject: [PATCH 2/2] xen: mask extended topology info in cpuid A Xen guest never needs to know about extended topology, and knowing would just confuse it. This patch just zeros ebx in leaf 0xb which indicates no topology info, preventing a crash under Xen on cpus which support this leaf. Signed-off-by: Jeremy Fitzhardinge Cc: Stable Kernel --- arch/x86/xen/enlighten.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 23a4d80fb39..dfbf70e6586 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -178,6 +178,7 @@ static __read_mostly unsigned int cpuid_leaf1_ecx_mask = ~0; static void xen_cpuid(unsigned int *ax, unsigned int *bx, unsigned int *cx, unsigned int *dx) { + unsigned maskebx = ~0; unsigned maskecx = ~0; unsigned maskedx = ~0; @@ -185,9 +186,16 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx, * Mask out inconvenient features, to try and disable as many * unsupported kernel subsystems as possible. */ - if (*ax == 1) { + switch (*ax) { + case 1: maskecx = cpuid_leaf1_ecx_mask; maskedx = cpuid_leaf1_edx_mask; + break; + + case 0xb: + /* Suppress extended topology stuff */ + maskebx = 0; + break; } asm(XEN_EMULATE_PREFIX "cpuid" @@ -197,6 +205,7 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx, "=d" (*dx) : "0" (*ax), "2" (*cx)); + *bx &= maskebx; *cx &= maskecx; *dx &= maskedx; }