* [PATCH] x86,kvm,vmx: Don't trap writes to CR4.TSD
@ 2014-10-08 0:16 Andy Lutomirski
2014-10-22 19:10 ` Andy Lutomirski
0 siblings, 1 reply; 3+ messages in thread
From: Andy Lutomirski @ 2014-10-08 0:16 UTC (permalink / raw)
To: Gleb Natapov, Paolo Bonzini; +Cc: kvm, Peter Zijlstra, Andy Lutomirski
CR4.TSD is guest-owned; don't trap writes to it in VMX guests. This
avoids a VM exit on context switches into or out of a PR_TSC_SIGSEGV
task.
I think that this fixes an unintentional side-effect of:
4c38609ac569 KVM: VMX: Make guest cr4 mask more conservative
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
arch/x86/kvm/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 54ca301f8415..0653233fcc82 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -105,7 +105,7 @@ module_param(nested, bool, S_IRUGO);
(KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
#define KVM_CR4_GUEST_OWNED_BITS \
(X86_CR4_PVI | X86_CR4_DE | X86_CR4_PCE | X86_CR4_OSFXSR \
- | X86_CR4_OSXMMEXCPT)
+ | X86_CR4_OSXMMEXCPT | X86_CR4_TSD)
#define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
#define KVM_RMODE_VM_CR4_ALWAYS_ON (X86_CR4_VME | X86_CR4_PAE | X86_CR4_VMXE)
--
1.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] x86,kvm,vmx: Don't trap writes to CR4.TSD
2014-10-08 0:16 [PATCH] x86,kvm,vmx: Don't trap writes to CR4.TSD Andy Lutomirski
@ 2014-10-22 19:10 ` Andy Lutomirski
2014-10-22 19:52 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Andy Lutomirski @ 2014-10-22 19:10 UTC (permalink / raw)
To: Gleb Natapov, Paolo Bonzini; +Cc: kvm list, Peter Zijlstra, Andy Lutomirski
On Tue, Oct 7, 2014 at 5:16 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> CR4.TSD is guest-owned; don't trap writes to it in VMX guests. This
> avoids a VM exit on context switches into or out of a PR_TSC_SIGSEGV
> task.
Friendly ping. I suspect this got lost in KVM Forum, etc.
--Andy
>
> I think that this fixes an unintentional side-effect of:
> 4c38609ac569 KVM: VMX: Make guest cr4 mask more conservative
>
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> ---
> arch/x86/kvm/vmx.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 54ca301f8415..0653233fcc82 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -105,7 +105,7 @@ module_param(nested, bool, S_IRUGO);
> (KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
> #define KVM_CR4_GUEST_OWNED_BITS \
> (X86_CR4_PVI | X86_CR4_DE | X86_CR4_PCE | X86_CR4_OSFXSR \
> - | X86_CR4_OSXMMEXCPT)
> + | X86_CR4_OSXMMEXCPT | X86_CR4_TSD)
>
> #define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
> #define KVM_RMODE_VM_CR4_ALWAYS_ON (X86_CR4_VME | X86_CR4_PAE | X86_CR4_VMXE)
> --
> 1.9.3
>
--
Andy Lutomirski
AMA Capital Management, LLC
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86,kvm,vmx: Don't trap writes to CR4.TSD
2014-10-22 19:10 ` Andy Lutomirski
@ 2014-10-22 19:52 ` Paolo Bonzini
0 siblings, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2014-10-22 19:52 UTC (permalink / raw)
To: Andy Lutomirski, Gleb Natapov; +Cc: kvm list, Peter Zijlstra
On 10/22/2014 09:10 PM, Andy Lutomirski wrote:
> On Tue, Oct 7, 2014 at 5:16 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>> CR4.TSD is guest-owned; don't trap writes to it in VMX guests. This
>> avoids a VM exit on context switches into or out of a PR_TSC_SIGSEGV
>> task.
>
> Friendly ping. I suspect this got lost in KVM Forum, etc.
Yup, will push tomorrow.
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-10-22 19:52 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-10-08 0:16 [PATCH] x86,kvm,vmx: Don't trap writes to CR4.TSD Andy Lutomirski
2014-10-22 19:10 ` Andy Lutomirski
2014-10-22 19:52 ` Paolo Bonzini
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.