From 9db2efd95e13330075bff027cd682a063d725332 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Thu, 14 Aug 2014 15:39:39 -0600 Subject: x86: Clear MTRRs on vCPU reset The SDM specifies (June 2014 Vol3 11.11.5): On a hardware reset, the P6 and more recent processors clear the valid flags in variable-range MTRRs and clear the E flag in the IA32_MTRR_DEF_TYPE MSR to disable all MTRRs. All other bits in the MTRRs are undefined. We currently do none of that, so whatever MTRR settings you had prior to reset is what you have after reset. Usually this doesn't matter because KVM often ignores the guest mappings and uses write-back anyway. However, if you have an assigned device and an IOMMU that allows NoSnoop for that device, KVM defers to the guest memory mappings which are now stale after reset. The result is that OVMF rebooting on such a configuration takes a full minute to LZMA decompress the firmware volume, a process that is nearly instant on the initial boot. Signed-off-by: Alex Williamson Reviewed-by: Laszlo Ersek Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini --- target-i386/cpu.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'target-i386/cpu.c') diff --git a/target-i386/cpu.c b/target-i386/cpu.c index 217500c735..52e335f145 100644 --- a/target-i386/cpu.c +++ b/target-i386/cpu.c @@ -2588,6 +2588,16 @@ static void x86_cpu_reset(CPUState *s) env->xcr0 = 1; + /* + * SDM 11.11.5 requires: + * - IA32_MTRR_DEF_TYPE MSR.E = 0 + * - IA32_MTRR_PHYSMASKn.V = 0 + * All other bits are undefined. For simplification, zero it all. + */ + env->mtrr_deftype = 0; + memset(env->mtrr_var, 0, sizeof(env->mtrr_var)); + memset(env->mtrr_fixed, 0, sizeof(env->mtrr_fixed)); + #if !defined(CONFIG_USER_ONLY) /* We hard-wire the BSP to the first CPU. */ if (s->cpu_index == 0) { -- cgit v1.2.3