From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51044) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bDpWc-0006ta-Fr for qemu-devel@nongnu.org; Fri, 17 Jun 2016 04:53:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bDpWX-0005fd-HC for qemu-devel@nongnu.org; Fri, 17 Jun 2016 04:53:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36906) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bDpWX-0005fY-8s for qemu-devel@nongnu.org; Fri, 17 Jun 2016 04:53:09 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B8C4A693F2 for ; Fri, 17 Jun 2016 08:53:08 +0000 (UTC) Date: Fri, 17 Jun 2016 09:53:05 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20160617085304.GE2273@work-vm> References: <1466097133-5489-1-git-send-email-dgilbert@redhat.com> <1466097133-5489-4-git-send-email-dgilbert@redhat.com> <20160616201408.GX18662@thinpad.lan.raisama.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160616201408.GX18662@thinpad.lan.raisama.net> Subject: Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, aarcange@redhat.com * Eduardo Habkost (ehabkost@redhat.com) wrote: > On Thu, Jun 16, 2016 at 06:12:11PM +0100, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" > > > > Fill the bits between 51..number-of-physical-address-bits in the > > MTRR_PHYSMASKn variable range mtrr masks so that they're consistent > > in the migration stream irrespective of the physical address space > > of the source VM in a migration. > > > > Signed-off-by: Dr. David Alan Gilbert > > Suggested-by: Paolo Bonzini > > --- > > include/hw/i386/pc.h | 5 +++++ > > target-i386/cpu.c | 1 + > > target-i386/cpu.h | 3 +++ > > target-i386/kvm.c | 25 ++++++++++++++++++++++++- > > 4 files changed, 33 insertions(+), 1 deletion(-) > > > > diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h > > index 49566c8..3883d04 100644 > > --- a/include/hw/i386/pc.h > > +++ b/include/hw/i386/pc.h > > @@ -362,6 +362,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *); > > .driver = TYPE_X86_CPU,\ > > .property = "cpuid-0xb",\ > > .value = "off",\ > > + },\ > > + {\ > > + .driver = TYPE_X86_CPU,\ > > + .property = "fill-mtrr-mask",\ > > + .value = "off",\ > > }, > > > > #define PC_COMPAT_2_5 \ > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > index f9302f9..4111240 100644 > > --- a/target-i386/cpu.c > > +++ b/target-i386/cpu.c > > @@ -3272,6 +3272,7 @@ static Property x86_cpu_properties[] = { > > DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true), > > DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false), > > DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true), > > + DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true), > > This is necessary only when phys_bits is higher on the > destination, right? Yes because otherwise the destination will mask it out. > Should we really default this to true? I would like to enable > this hack only when really necessary. Except when using host's > phys_bits (phys-bits=0), is there any valid reason to expect > higher phys-bits on the destination? Who is to say? With the current default of 40 we've not been setting these higher bits when going from 39-46 bit systems for years; I'm not sure what the consequence has been. Dave > > > > > DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, 0), > > DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, 0), > > DEFINE_PROP_UINT32("xlevel2", X86CPU, env.cpuid_xlevel2, 0), > > diff --git a/target-i386/cpu.h b/target-i386/cpu.h > > index 61c06b7..13d8501 100644 > > --- a/target-i386/cpu.h > > +++ b/target-i386/cpu.h > > @@ -1181,6 +1181,9 @@ struct X86CPU { > > /* Compatibility bits for old machine types: */ > > bool enable_cpuid_0xb; > > > > + /* if true fill the top bits of the MTRR_PHYSMASKn variable range */ > > + bool fill_mtrr_mask; > > + > > /* in order to simplify APIC support, we leave this pointer to the > > user */ > > struct DeviceState *apic_state; > > diff --git a/target-i386/kvm.c b/target-i386/kvm.c > > index d95d06b..9b5158e 100644 > > --- a/target-i386/kvm.c > > +++ b/target-i386/kvm.c > > @@ -1934,6 +1934,7 @@ static int kvm_get_msrs(X86CPU *cpu) > > CPUX86State *env = &cpu->env; > > struct kvm_msr_entry *msrs = cpu->kvm_msr_buf->entries; > > int ret, i; > > + uint64_t mtrr_top_bits; > > > > kvm_msr_buf_reset(cpu); > > > > @@ -2083,6 +2084,27 @@ static int kvm_get_msrs(X86CPU *cpu) > > } > > > > assert(ret == cpu->kvm_msr_buf->nmsrs); > > + /* > > + * MTRR masks: Each mask consists of 5 parts > > + * a 10..0: must be zero > > + * b 11 : valid bit > > + * c n-1.12: actual mask bits > > + * d 51..n: reserved must be zero > > + * e 63.52: reserved must be zero > > + * > > + * 'n' is the number of physical bits supported by the CPU and is > > + * apparently always <= 52. We know our 'n' but don't know what > > + * the destinations 'n' is; it might be smaller, in which case > > + * it masks (c) on loading. It might be larger, in which case > > + * we fill 'd' so that d..c is consistent irrespetive of the 'n' > > + * we're migrating to. > > + */ > > + if (cpu->fill_mtrr_mask) { > > + mtrr_top_bits = BIT_RANGE(51, cpu_x86_guest_phys_address_bits(env)); > > + } else { > > + mtrr_top_bits = 0; > > + } > > + > > for (i = 0; i < ret; i++) { > > uint32_t index = msrs[i].index; > > switch (index) { > > @@ -2278,7 +2300,8 @@ static int kvm_get_msrs(X86CPU *cpu) > > break; > > case MSR_MTRRphysBase(0) ... MSR_MTRRphysMask(MSR_MTRRcap_VCNT - 1): > > if (index & 1) { > > - env->mtrr_var[MSR_MTRRphysIndex(index)].mask = msrs[i].data; > > + env->mtrr_var[MSR_MTRRphysIndex(index)].mask = msrs[i].data | > > + mtrr_top_bits; > > } else { > > env->mtrr_var[MSR_MTRRphysIndex(index)].base = msrs[i].data; > > } > > -- > > 2.7.4 > > > > -- > Eduardo -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK