FAILED: patch "[PATCH] KVM: x86: Use adjustment in guest cycles when handling" failed to apply to 4.2-stable tree

FAILED: patch "[PATCH] KVM: x86: Use adjustment in guest cycles when handling" failed to apply to 4.2-stable tree

[gregkh]

The patch below does not apply to the 4.2-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From d7add05458084a5e3d65925764a02ca9c8202c1e Mon Sep 17 00:00:00 2001
From: Haozhong Zhang <haozhong.zhang@intel.com>
Date: Fri, 7 Aug 2015 11:24:32 +0800
Subject: [PATCH] KVM: x86: Use adjustment in guest cycles when handling
 MSR_IA32_TSC_ADJUST

When kvm_set_msr_common() handles a guest's write to
MSR_IA32_TSC_ADJUST, it will calcuate an adjustment based on the data
written by guest and then use it to adjust TSC offset by calling a
call-back adjust_tsc_offset(). The 3rd parameter of adjust_tsc_offset()
indicates whether the adjustment is in host TSC cycles or in guest TSC
cycles. If SVM TSC scaling is enabled, adjust_tsc_offset()
[i.e. svm_adjust_tsc_offset()] will first scale the adjustment;
otherwise, it will just use the unscaled one. As the MSR write here
comes from the guest, the adjustment is in guest TSC cycles. However,
the current kvm_set_msr_common() uses it as a value in host TSC
cycles (by using true as the 3rd parameter of adjust_tsc_offset()),
which can result in an incorrect adjustment of TSC offset if SVM TSC
scaling is enabled. This patch fixes this problem.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Cc: stable@vger.linux.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c5e88a881899..8f0f6eca69da 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2105,7 +2105,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (guest_cpuid_has_tsc_adjust(vcpu)) {
 			if (!msr_info->host_initiated) {
 				s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr;
-				kvm_x86_ops->adjust_tsc_offset(vcpu, adj, true);
+				adjust_tsc_offset_guest(vcpu, adj);
 			}
 			vcpu->arch.ia32_tsc_adjust_msr = data;
 		}

Re: FAILED: patch "[PATCH] KVM: x86: Use adjustment in guest cycles when handling" failed to apply to 4.2-stable tree

[Haozhong Zhang]

On Wed, Sep 16, 2015 at 10:05:54PM -0700, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.2-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> thanks,
> 
> greg k-h
>

Hi greg,

I found this patch is already in the 4.2-stable tree (commit id d7add05).

Thanks,
- Haozhong

> ------------------ original commit in Linus's tree ------------------
> 
> From d7add05458084a5e3d65925764a02ca9c8202c1e Mon Sep 17 00:00:00 2001
> From: Haozhong Zhang <haozhong.zhang@intel.com>
> Date: Fri, 7 Aug 2015 11:24:32 +0800
> Subject: [PATCH] KVM: x86: Use adjustment in guest cycles when handling
>  MSR_IA32_TSC_ADJUST
> 
> When kvm_set_msr_common() handles a guest's write to
> MSR_IA32_TSC_ADJUST, it will calcuate an adjustment based on the data
> written by guest and then use it to adjust TSC offset by calling a
> call-back adjust_tsc_offset(). The 3rd parameter of adjust_tsc_offset()
> indicates whether the adjustment is in host TSC cycles or in guest TSC
> cycles. If SVM TSC scaling is enabled, adjust_tsc_offset()
> [i.e. svm_adjust_tsc_offset()] will first scale the adjustment;
> otherwise, it will just use the unscaled one. As the MSR write here
> comes from the guest, the adjustment is in guest TSC cycles. However,
> the current kvm_set_msr_common() uses it as a value in host TSC
> cycles (by using true as the 3rd parameter of adjust_tsc_offset()),
> which can result in an incorrect adjustment of TSC offset if SVM TSC
> scaling is enabled. This patch fixes this problem.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> Cc: stable@vger.linux.org
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c5e88a881899..8f0f6eca69da 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2105,7 +2105,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		if (guest_cpuid_has_tsc_adjust(vcpu)) {
>  			if (!msr_info->host_initiated) {
>  				s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr;
> -				kvm_x86_ops->adjust_tsc_offset(vcpu, adj, true);
> +				adjust_tsc_offset_guest(vcpu, adj);
>  			}
>  			vcpu->arch.ia32_tsc_adjust_msr = data;
>  		}
>

Re: FAILED: patch "[PATCH] KVM: x86: Use adjustment in guest cycles when handling" failed to apply to 4.2-stable tree

[Greg KH]

On Thu, Sep 17, 2015 at 02:24:33PM +0800, Haozhong Zhang wrote:
> On Wed, Sep 16, 2015 at 10:05:54PM -0700, gregkh@linuxfoundation.org wrote:
> > 
> > The patch below does not apply to the 4.2-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> > 
> > thanks,
> > 
> > greg k-h
> >
> 
> Hi greg,
> 
> I found this patch is already in the 4.2-stable tree (commit id d7add05).

Yeah, my fault, sorry about that, it's now in the 4.1-stable queue.

greg k-h