From: Igor Druzhinin Date: Thu, 5 Mar 2020 10:29:39 +0000 (+0100) Subject: x86/time: update TSC stamp on restore from deep C-state X-Git-Tag: archive/raspbian/4.11.4-1+rpi1^2~58^2~29 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=06adda76b680f741ea1a3517adddb11bf93536d5;p=xen.git x86/time: update TSC stamp on restore from deep C-state If ITSC is not available on CPU (e.g if running nested as PV shim) then X86_FEATURE_NONSTOP_TSC is not advertised in certain cases, i.e. all AMD and some old Intel processors. In which case TSC would need to be restored on CPU from platform time by Xen upon exiting C-states. As platform time might be behind the last TSC stamp recorded for the current CPU, invariant of TSC stamp being always behind local TSC counter is violated. This has an effect of get_s_time() going negative resulting in eventual system hang or crash. Fix this issue by updating local TSC stamp along with TSC counter write. Signed-off-by: Igor Druzhinin Reviewed-by: Roger Pau Monné Acked-by: Jan Beulich master commit: bbf283f853f8c0e4d29248dd44d3b0e0abc07629 master date: 2020-01-17 16:11:20 +0100 --- diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index 430fba1e66..373b10b6dc 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -854,10 +854,16 @@ u64 stime2tsc(s_time_t stime) void cstate_restore_tsc(void) { + struct cpu_time *t = &this_cpu(cpu_time); + if ( boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ) return; - write_tsc(stime2tsc(read_platform_stime(NULL))); + t->stamp.master_stime = read_platform_stime(NULL); + t->stamp.local_tsc = stime2tsc(t->stamp.master_stime); + t->stamp.local_stime = t->stamp.master_stime; + + write_tsc(t->stamp.local_tsc); } /***************************************************************************