It was found that AWS x1 instances (Xen-based) lack xen.git commit 1f1d183d4900 (x86/HVM: don't give the wrong impression of WRMSR succeeding) and because of that the wrmsr_safe() check in cache_alloc_hsw_probe() doesn't help: the consequent rdmsr() blows up with
unchecked MSR access error: RDMSR from 0xc90 at rIP: 0xffffffff88c5bba3 (native_read_msr+0x3/0x30) The issue should definitely get fixed on AWS side. We can, however, simply workaround this in Linux and live happily after. Signed-off-by: Vitaly Kuznetsov <[email protected]> --- arch/x86/kernel/cpu/intel_rdt.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c index 44272b7107ad..0acee6cd07a8 100644 --- a/arch/x86/kernel/cpu/intel_rdt.c +++ b/arch/x86/kernel/cpu/intel_rdt.c @@ -213,7 +213,8 @@ static inline void cache_alloc_hsw_probe(void) if (wrmsr_safe(IA32_L3_CBM_BASE, max_cbm, 0)) return; - rdmsr(IA32_L3_CBM_BASE, l, h); + if (rdmsr_safe(IA32_L3_CBM_BASE, &l, &h)) + return; /* If all the bits were set in MSR, return success */ if (l != max_cbm) -- 2.19.2
