* [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
@ 2015-04-16 18:58 Ben Serebrin
2015-04-16 20:42 ` Venkatesh Srinivas
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: Ben Serebrin @ 2015-04-16 18:58 UTC (permalink / raw)
To: kvm, stable, luto, pbonzini, jankiszka; +Cc: serebrin
The host's decision to enable machine check exceptions should remain
in force during non-root mode. KVM was writing 0 to cr4 on VCPU reset
and passed a slightly-modified 0 to the vmcs.guest_cr4 value.
Tested: Built.
On earlier version, tested by injecting machine check
while a guest is spinning.
Before the change, if guest CR4.MCE==0, then the machine check is
escalated to Catastrophic Error (CATERR) and the machine dies.
If guest CR4.MCE==1, then the machine check causes VMEXIT and is
handled normally by host Linux. After the change, injecting a machine
check causes normal Linux machine check handling.
Signed-off-by: Ben Serebrin <serebrin@google.com>
---
arch/x86/kvm/vmx.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f5e8dce..f7b6168 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3622,8 +3622,16 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
- unsigned long hw_cr4 = cr4 | (to_vmx(vcpu)->rmode.vm86_active ?
- KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
+ /*
+ * Pass through host's Machine Check Enable value to hw_cr4, which
+ * is in force while we are in guest mode. Do not let guests control
+ * this bit, even if host CR4.MCE == 0.
+ */
+ unsigned long hw_cr4 =
+ (cr4_read_shadow() & X86_CR4_MCE) |
+ (cr4 & ~X86_CR4_MCE) |
+ (to_vmx(vcpu)->rmode.vm86_active ?
+ KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
if (cr4 & X86_CR4_VMXE) {
/*
--
2.2.0.rc0.207.ga3a616c
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
2015-04-16 18:58 [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode Ben Serebrin
@ 2015-04-16 20:42 ` Venkatesh Srinivas
2015-04-17 5:10 ` Wanpeng Li
2015-04-17 8:55 ` Greg KH
2 siblings, 0 replies; 8+ messages in thread
From: Venkatesh Srinivas @ 2015-04-16 20:42 UTC (permalink / raw)
To: Ben Serebrin; +Cc: kvm, stable, luto, Paolo Bonzini, jankiszka
On Thu, Apr 16, 2015 at 11:58 AM, Ben Serebrin <serebrin@google.com> wrote:
> The host's decision to enable machine check exceptions should remain
> in force during non-root mode. KVM was writing 0 to cr4 on VCPU reset
> and passed a slightly-modified 0 to the vmcs.guest_cr4 value.
>
> Tested: Built.
> On earlier version, tested by injecting machine check
> while a guest is spinning.
>
> Before the change, if guest CR4.MCE==0, then the machine check is
> escalated to Catastrophic Error (CATERR) and the machine dies.
> If guest CR4.MCE==1, then the machine check causes VMEXIT and is
> handled normally by host Linux. After the change, injecting a machine
> check causes normal Linux machine check handling.
>
> Signed-off-by: Ben Serebrin <serebrin@google.com>
> ---
> arch/x86/kvm/vmx.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f5e8dce..f7b6168 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3622,8 +3622,16 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>
> static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> {
> - unsigned long hw_cr4 = cr4 | (to_vmx(vcpu)->rmode.vm86_active ?
> - KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
> + /*
> + * Pass through host's Machine Check Enable value to hw_cr4, which
> + * is in force while we are in guest mode. Do not let guests control
> + * this bit, even if host CR4.MCE == 0.
> + */
> + unsigned long hw_cr4 =
> + (cr4_read_shadow() & X86_CR4_MCE) |
> + (cr4 & ~X86_CR4_MCE) |
> + (to_vmx(vcpu)->rmode.vm86_active ?
> + KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
>
> if (cr4 & X86_CR4_VMXE) {
> /*
> --
> 2.2.0.rc0.207.ga3a616c
Signed-off-by: Venkatesh Srinivas <venkateshs@google.com>
-- vs;
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
2015-04-16 18:58 [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode Ben Serebrin
2015-04-16 20:42 ` Venkatesh Srinivas
@ 2015-04-17 5:10 ` Wanpeng Li
2015-04-17 10:16 ` Paolo Bonzini
2015-04-17 8:55 ` Greg KH
2 siblings, 1 reply; 8+ messages in thread
From: Wanpeng Li @ 2015-04-17 5:10 UTC (permalink / raw)
To: Ben Serebrin; +Cc: kvm, stable, luto, pbonzini, jankiszka, Wanpeng Li
Hi Ben,
On Thu, Apr 16, 2015 at 11:58:05AM -0700, Ben Serebrin wrote:
>The host's decision to enable machine check exceptions should remain
>in force during non-root mode. KVM was writing 0 to cr4 on VCPU reset
>and passed a slightly-modified 0 to the vmcs.guest_cr4 value.
>
>Tested: Built.
>On earlier version, tested by injecting machine check
>while a guest is spinning.
>
>Before the change, if guest CR4.MCE==0, then the machine check is
>escalated to Catastrophic Error (CATERR) and the machine dies.
Could you point out which section of SDM describes that the machine check
is escalated to a CATERR if CR4.MCE==0?
Regards,
Wanpeng Li
>If guest CR4.MCE==1, then the machine check causes VMEXIT and is
>handled normally by host Linux. After the change, injecting a machine
>check causes normal Linux machine check handling.
>
>Signed-off-by: Ben Serebrin <serebrin@google.com>
>---
> arch/x86/kvm/vmx.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
>diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>index f5e8dce..f7b6168 100644
>--- a/arch/x86/kvm/vmx.c
>+++ b/arch/x86/kvm/vmx.c
>@@ -3622,8 +3622,16 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>
> static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> {
>- unsigned long hw_cr4 = cr4 | (to_vmx(vcpu)->rmode.vm86_active ?
>- KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
>+ /*
>+ * Pass through host's Machine Check Enable value to hw_cr4, which
>+ * is in force while we are in guest mode. Do not let guests control
>+ * this bit, even if host CR4.MCE == 0.
>+ */
>+ unsigned long hw_cr4 =
>+ (cr4_read_shadow() & X86_CR4_MCE) |
>+ (cr4 & ~X86_CR4_MCE) |
>+ (to_vmx(vcpu)->rmode.vm86_active ?
>+ KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
>
> if (cr4 & X86_CR4_VMXE) {
> /*
>--
>2.2.0.rc0.207.ga3a616c
>
>--
>To unsubscribe from this list: send the line "unsubscribe kvm" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
2015-04-16 18:58 [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode Ben Serebrin
2015-04-16 20:42 ` Venkatesh Srinivas
2015-04-17 5:10 ` Wanpeng Li
@ 2015-04-17 8:55 ` Greg KH
2015-04-17 10:10 ` Paolo Bonzini
2 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2015-04-17 8:55 UTC (permalink / raw)
To: Ben Serebrin; +Cc: kvm, stable, luto, pbonzini, jankiszka
On Thu, Apr 16, 2015 at 11:58:05AM -0700, Ben Serebrin wrote:
> The host's decision to enable machine check exceptions should remain
> in force during non-root mode. KVM was writing 0 to cr4 on VCPU reset
> and passed a slightly-modified 0 to the vmcs.guest_cr4 value.
>
> Tested: Built.
> On earlier version, tested by injecting machine check
> while a guest is spinning.
>
> Before the change, if guest CR4.MCE==0, then the machine check is
> escalated to Catastrophic Error (CATERR) and the machine dies.
> If guest CR4.MCE==1, then the machine check causes VMEXIT and is
> handled normally by host Linux. After the change, injecting a machine
> check causes normal Linux machine check handling.
>
> Signed-off-by: Ben Serebrin <serebrin@google.com>
> ---
> arch/x86/kvm/vmx.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read Documentation/stable_kernel_rules.txt
for how to do this properly.
</formletter>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
2015-04-17 8:55 ` Greg KH
@ 2015-04-17 10:10 ` Paolo Bonzini
0 siblings, 0 replies; 8+ messages in thread
From: Paolo Bonzini @ 2015-04-17 10:10 UTC (permalink / raw)
To: Greg KH, Ben Serebrin; +Cc: kvm, stable, luto, jankiszka
On 17/04/2015 10:55, Greg KH wrote:
> On Thu, Apr 16, 2015 at 11:58:05AM -0700, Ben Serebrin wrote:
>> > The host's decision to enable machine check exceptions should remain
>> > in force during non-root mode. KVM was writing 0 to cr4 on VCPU reset
>> > and passed a slightly-modified 0 to the vmcs.guest_cr4 value.
>> >
>> > Tested: Built.
>> > On earlier version, tested by injecting machine check
>> > while a guest is spinning.
>> >
>> > Before the change, if guest CR4.MCE==0, then the machine check is
>> > escalated to Catastrophic Error (CATERR) and the machine dies.
>> > If guest CR4.MCE==1, then the machine check causes VMEXIT and is
>> > handled normally by host Linux. After the change, injecting a machine
>> > check causes normal Linux machine check handling.
>> >
>> > Signed-off-by: Ben Serebrin <serebrin@google.com>
>> > ---
>> > arch/x86/kvm/vmx.c | 12 ++++++++++--
>> > 1 file changed, 10 insertions(+), 2 deletions(-)
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree. Please read Documentation/stable_kernel_rules.txt
> for how to do this properly.
I'll fix it up when applying to the KVM tree.
Paolo
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
2015-04-17 5:10 ` Wanpeng Li
@ 2015-04-17 10:16 ` Paolo Bonzini
2015-04-17 16:03 ` Benjamin Serebrin
2015-04-19 22:59 ` Wanpeng Li
0 siblings, 2 replies; 8+ messages in thread
From: Paolo Bonzini @ 2015-04-17 10:16 UTC (permalink / raw)
To: Wanpeng Li, Ben Serebrin; +Cc: kvm, stable, luto, jankiszka
On 17/04/2015 07:10, Wanpeng Li wrote:
>> >
>> >Before the change, if guest CR4.MCE==0, then the machine check is
>> >escalated to Catastrophic Error (CATERR) and the machine dies.
> Could you point out which section of SDM describes that the machine check
> is escalated to a CATERR if CR4.MCE==0?
It's under the description of "Interrupt 18--Machine-Check Exception (#MC)":
The machine-check mechanism is enabled by setting the MCE flag in
control register CR4. [...] If the machine-check mechanism is not
enabled (the MCE flag in control register CR4 is clear), a
machine-check exception causes the processor to enter the shutdown
state.
This of course also applies whenever the non-root mode CR4 (*not* the
shadow CR4 in the VMCS!) has the MCE flag cleared.
Paolo
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
2015-04-17 10:16 ` Paolo Bonzini
@ 2015-04-17 16:03 ` Benjamin Serebrin
2015-04-19 22:59 ` Wanpeng Li
1 sibling, 0 replies; 8+ messages in thread
From: Benjamin Serebrin @ 2015-04-17 16:03 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Wanpeng Li, kvm, stable, luto, jankiszka
Thanks, Paolo, for the document reference and the fixup.
Greg: Sorry for the standard newbie gaffs.
On Fri, Apr 17, 2015 at 3:16 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
>
> On 17/04/2015 07:10, Wanpeng Li wrote:
>>> >
>>> >Before the change, if guest CR4.MCE==0, then the machine check is
>>> >escalated to Catastrophic Error (CATERR) and the machine dies.
>> Could you point out which section of SDM describes that the machine check
>> is escalated to a CATERR if CR4.MCE==0?
>
> It's under the description of "Interrupt 18--Machine-Check Exception (#MC)":
>
> The machine-check mechanism is enabled by setting the MCE flag in
> control register CR4. [...] If the machine-check mechanism is not
> enabled (the MCE flag in control register CR4 is clear), a
> machine-check exception causes the processor to enter the shutdown
> state.
>
> This of course also applies whenever the non-root mode CR4 (*not* the
> shadow CR4 in the VMCS!) has the MCE flag cleared.
>
> Paolo
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode.
2015-04-17 10:16 ` Paolo Bonzini
2015-04-17 16:03 ` Benjamin Serebrin
@ 2015-04-19 22:59 ` Wanpeng Li
1 sibling, 0 replies; 8+ messages in thread
From: Wanpeng Li @ 2015-04-19 22:59 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Ben Serebrin, kvm, stable, luto, jankiszka
On Fri, Apr 17, 2015 at 12:16:18PM +0200, Paolo Bonzini wrote:
>
>
>On 17/04/2015 07:10, Wanpeng Li wrote:
>>> >
>>> >Before the change, if guest CR4.MCE==0, then the machine check is
>>> >escalated to Catastrophic Error (CATERR) and the machine dies.
>> Could you point out which section of SDM describes that the machine check
>> is escalated to a CATERR if CR4.MCE==0?
>
>It's under the description of "Interrupt 18--Machine-Check Exception (#MC)":
>
> The machine-check mechanism is enabled by setting the MCE flag in
> control register CR4. [...] If the machine-check mechanism is not
> enabled (the MCE flag in control register CR4 is clear), a
> machine-check exception causes the processor to enter the shutdown
> state.
>
>This of course also applies whenever the non-root mode CR4 (*not* the
>shadow CR4 in the VMCS!) has the MCE flag cleared.
Got it, thanks, :)
Regards,
Wanpeng Li
>
>Paolo
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2015-04-19 22:59 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-04-16 18:58 [PATCH] KVM: VMX: Preserve host CR4.MCE value while in guest mode Ben Serebrin
2015-04-16 20:42 ` Venkatesh Srinivas
2015-04-17 5:10 ` Wanpeng Li
2015-04-17 10:16 ` Paolo Bonzini
2015-04-17 16:03 ` Benjamin Serebrin
2015-04-19 22:59 ` Wanpeng Li
2015-04-17 8:55 ` Greg KH
2015-04-17 10:10 ` Paolo Bonzini
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