* [PATCH] No need to emulate WBINVD when VT-d force snooping feature available
@ 2010-07-05 3:46 Sheng Yang
2010-07-05 9:36 ` Ian Pratt
0 siblings, 1 reply; 3+ messages in thread
From: Sheng Yang @ 2010-07-05 3:46 UTC (permalink / raw)
To: Keir Fraser; +Cc: xen-devel@lists.xensource.com
[-- Attachment #1: Type: Text/Plain, Size: 1195 bytes --]
There is no cache coherency issue if VT-d engine's force snooping feature
available.
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1064,8 +1064,10 @@
* 1: flushing cache (wbinvd) when the guest is scheduled out if
* there is no wbinvd exit, or
* 2: execute wbinvd on all dirty pCPUs when guest wbinvd exits.
+ * If VT-d engine can force snooping, we don't need to do these.
*/
- if ( has_arch_pdevs(v->domain) && !cpu_has_wbinvd_exiting )
+ if ( has_arch_pdevs(v->domain) && !iommu_snoop
+ && !cpu_has_wbinvd_exiting )
{
int cpu = v->arch.hvm_vmx.active_cpu;
if ( cpu != -1 )
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2089,6 +2089,9 @@
if ( !has_arch_mmios(current->domain) )
return;
+ if ( iommu_snoop )
+ return;
+
if ( cpu_has_wbinvd_exiting )
on_each_cpu(wbinvd_ipi, NULL, 1);
else
[-- Attachment #2: iommu_snp_wbinvd.patch --]
[-- Type: text/x-patch, Size: 1058 bytes --]
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1064,8 +1064,10 @@
* 1: flushing cache (wbinvd) when the guest is scheduled out if
* there is no wbinvd exit, or
* 2: execute wbinvd on all dirty pCPUs when guest wbinvd exits.
+ * If VT-d engine can force snooping, we don't need to do these.
*/
- if ( has_arch_pdevs(v->domain) && !cpu_has_wbinvd_exiting )
+ if ( has_arch_pdevs(v->domain) && !iommu_snoop
+ && !cpu_has_wbinvd_exiting )
{
int cpu = v->arch.hvm_vmx.active_cpu;
if ( cpu != -1 )
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2089,6 +2089,9 @@
if ( !has_arch_mmios(current->domain) )
return;
+ if ( iommu_snoop )
+ return;
+
if ( cpu_has_wbinvd_exiting )
on_each_cpu(wbinvd_ipi, NULL, 1);
else
[-- Attachment #3: Type: text/plain, Size: 138 bytes --]
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^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: [PATCH] No need to emulate WBINVD when VT-d force snooping feature available
2010-07-05 3:46 [PATCH] No need to emulate WBINVD when VT-d force snooping feature available Sheng Yang
@ 2010-07-05 9:36 ` Ian Pratt
2010-07-05 10:09 ` Keir Fraser
0 siblings, 1 reply; 3+ messages in thread
From: Ian Pratt @ 2010-07-05 9:36 UTC (permalink / raw)
To: Sheng Yang, Keir Fraser; +Cc: Ian Pratt, xen-devel@lists.xensource.com
> There is no cache coherency issue if VT-d engine's force snooping feature
> available.
Isn't it also necessary to explicitly set the SNP bit in each VTd PTE to force snooping? I don't believe we do this today, but since we ignore guest PAT settings on RAM we should do so.
Thanks,
Ian
> Signed-off-by: Sheng Yang <sheng@linux.intel.com>
>
> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -1064,8 +1064,10 @@
> * 1: flushing cache (wbinvd) when the guest is scheduled out if
> * there is no wbinvd exit, or
> * 2: execute wbinvd on all dirty pCPUs when guest wbinvd exits.
> + * If VT-d engine can force snooping, we don't need to do these.
> */
> - if ( has_arch_pdevs(v->domain) && !cpu_has_wbinvd_exiting )
> + if ( has_arch_pdevs(v->domain) && !iommu_snoop
> + && !cpu_has_wbinvd_exiting )
> {
> int cpu = v->arch.hvm_vmx.active_cpu;
> if ( cpu != -1 )
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2089,6 +2089,9 @@
> if ( !has_arch_mmios(current->domain) )
> return;
>
> + if ( iommu_snoop )
> + return;
> +
> if ( cpu_has_wbinvd_exiting )
> on_each_cpu(wbinvd_ipi, NULL, 1);
> else
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] No need to emulate WBINVD when VT-d force snooping feature available
2010-07-05 9:36 ` Ian Pratt
@ 2010-07-05 10:09 ` Keir Fraser
0 siblings, 0 replies; 3+ messages in thread
From: Keir Fraser @ 2010-07-05 10:09 UTC (permalink / raw)
To: Ian Pratt, Sheng Yang; +Cc: xen-devel@lists.xensource.com
On 05/07/2010 10:36, "Ian Pratt" <Ian.Pratt@eu.citrix.com> wrote:
>> There is no cache coherency issue if VT-d engine's force snooping feature
>> available.
>
> Isn't it also necessary to explicitly set the SNP bit in each VTd PTE to force
> snooping? I don't believe we do this today, but since we ignore guest PAT
> settings on RAM we should do so.
In drivers/passthrough/vtd/iommu.c:intel_iommu_map_page() ---
/* Set the SNP on leaf page table if Snoop Control available */
if ( iommu_snoop )
dma_set_pte_snp(*pte);
-- Keir
> Thanks,
> Ian
>
>
>> Signed-off-by: Sheng Yang <sheng@linux.intel.com>
>>
>> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
>> --- a/xen/arch/x86/hvm/vmx/vmcs.c
>> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
>> @@ -1064,8 +1064,10 @@
>> * 1: flushing cache (wbinvd) when the guest is scheduled out if
>> * there is no wbinvd exit, or
>> * 2: execute wbinvd on all dirty pCPUs when guest wbinvd exits.
>> + * If VT-d engine can force snooping, we don't need to do these.
>> */
>> - if ( has_arch_pdevs(v->domain) && !cpu_has_wbinvd_exiting )
>> + if ( has_arch_pdevs(v->domain) && !iommu_snoop
>> + && !cpu_has_wbinvd_exiting )
>> {
>> int cpu = v->arch.hvm_vmx.active_cpu;
>> if ( cpu != -1 )
>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> @@ -2089,6 +2089,9 @@
>> if ( !has_arch_mmios(current->domain) )
>> return;
>>
>> + if ( iommu_snoop )
>> + return;
>> +
>> if ( cpu_has_wbinvd_exiting )
>> on_each_cpu(wbinvd_ipi, NULL, 1);
>> else
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2010-07-05 10:09 UTC | newest]
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2010-07-05 3:46 [PATCH] No need to emulate WBINVD when VT-d force snooping feature available Sheng Yang
2010-07-05 9:36 ` Ian Pratt
2010-07-05 10:09 ` Keir Fraser
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