[PATCH v2 0/2] Virtual GIF

[PATCH v2 0/2] Virtual GIF

[Brian Woods]

On AMD family 17h processors, there is a feature called virtual GIF.
This allows a nested hypervisor to preform a CLGI or STGI without
needing to be intercepted by the host hypervisor.  For more information
about it please see:

AMD64 Architecture Programmer’s Manual Volume 2: System Programming
http://support.amd.com/TechDocs/24593.pdf
Section: Virtual GIF (Section 15.33.2)

This patch series adds support to check for and enable the virtual
GIF features if available.

These patches were tested on a AMD family 17h (EPYC 7401) system.

Brian Woods (2):
  x86/svm: Add virtual GIF feature definition
  x86/svm: Add virtual GIF support

 xen/arch/x86/hvm/svm/nestedsvm.c   |  7 ++++++-
 xen/arch/x86/hvm/svm/svm.c         |  1 +
 xen/arch/x86/hvm/svm/vmcb.c        | 12 ++++++++++++
 xen/include/asm-x86/hvm/svm/svm.h  |  2 ++
 xen/include/asm-x86/hvm/svm/vmcb.h |  6 ++++--
 5 files changed, 25 insertions(+), 3 deletions(-)

-- 
2.11.0


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[PATCH v2 1/2] x86/svm: Add virtual GIF feature definition

[Brian Woods]

Add support for enabling the virtual GIF feature.

Signed-off-by: Brian Woods <brian.woods@amd.com>
---
 xen/include/asm-x86/hvm/svm/svm.h  | 2 ++
 xen/include/asm-x86/hvm/svm/vmcb.h | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/xen/include/asm-x86/hvm/svm/svm.h b/xen/include/asm-x86/hvm/svm/svm.h
index 0956f860ef..ec1eda6a3e 100644
--- a/xen/include/asm-x86/hvm/svm/svm.h
+++ b/xen/include/asm-x86/hvm/svm/svm.h
@@ -64,6 +64,7 @@ extern u32 svm_feature_flags;
 #define SVM_FEATURE_FLUSHBYASID    6 /* TLB flush by ASID support */
 #define SVM_FEATURE_DECODEASSISTS  7 /* Decode assists support */
 #define SVM_FEATURE_PAUSEFILTER   10 /* Pause intercept filter support */
+#define SVM_FEATURE_VGIF          16 /* Virtual GIF */
 
 #define cpu_has_svm_feature(f) test_bit(f, &svm_feature_flags)
 #define cpu_has_svm_npt       cpu_has_svm_feature(SVM_FEATURE_NPT)
@@ -72,6 +73,7 @@ extern u32 svm_feature_flags;
 #define cpu_has_svm_nrips     cpu_has_svm_feature(SVM_FEATURE_NRIPS)
 #define cpu_has_svm_cleanbits cpu_has_svm_feature(SVM_FEATURE_VMCBCLEAN)
 #define cpu_has_svm_decode    cpu_has_svm_feature(SVM_FEATURE_DECODEASSISTS)
+#define cpu_has_svm_vgif      cpu_has_svm_feature(SVM_FEATURE_VGIF)
 #define cpu_has_pause_filter  cpu_has_svm_feature(SVM_FEATURE_PAUSEFILTER)
 #define cpu_has_tsc_ratio     cpu_has_svm_feature(SVM_FEATURE_TSCRATEMSR)
 
diff --git a/xen/include/asm-x86/hvm/svm/vmcb.h b/xen/include/asm-x86/hvm/svm/vmcb.h
index 01ce20b0bd..595cfcf57b 100644
--- a/xen/include/asm-x86/hvm/svm/vmcb.h
+++ b/xen/include/asm-x86/hvm/svm/vmcb.h
@@ -325,12 +325,14 @@ typedef union
     {
         u64 tpr:          8;
         u64 irq:          1;
-        u64 rsvd0:        7;
+        u64 vgif:         1;
+        u64 rsvd0:        6;
         u64 prio:         4;
         u64 ign_tpr:      1;
         u64 rsvd1:        3;
         u64 intr_masking: 1;
-        u64 rsvd2:        7;
+        u64 vgif_enable:  1;
+        u64 rsvd2:        6;
         u64 vector:       8;
         u64 rsvd3:       24;
     } fields;
-- 
2.11.0


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[PATCH v2 2/2] x86/svm: Add virtual GIF support

[Brian Woods]

This patch detects and enables Virtual GIF if available.  This allows
a nested hypervisor to perform STGIs and CLGIs without having to be
intercepted by host hypervisor.

Signed-off-by: Brian Woods <brian.woods@amd.com>
---
 xen/arch/x86/hvm/svm/nestedsvm.c |  7 ++++++-
 xen/arch/x86/hvm/svm/svm.c       |  1 +
 xen/arch/x86/hvm/svm/vmcb.c      | 12 ++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/svm/nestedsvm.c b/xen/arch/x86/hvm/svm/nestedsvm.c
index 1de896e456..0705cf9cb8 100644
--- a/xen/arch/x86/hvm/svm/nestedsvm.c
+++ b/xen/arch/x86/hvm/svm/nestedsvm.c
@@ -1597,8 +1597,13 @@ bool_t
 nestedsvm_gif_isset(struct vcpu *v)
 {
     struct nestedsvm *svm = &vcpu_nestedsvm(v);
+    struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
 
-    return (!!svm->ns_gif);
+    /* get the vmcb gif value if using vgif */
+    if ( vmcb->_vintr.fields.vgif_enable )
+        return vmcb->_vintr.fields.vgif;
+    else
+        return svm->ns_gif;
 }
 
 void svm_vmexit_do_stgi(struct cpu_user_regs *regs, struct vcpu *v)
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index b9cf423fd9..6b7a462fcb 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1669,6 +1669,7 @@ const struct hvm_function_table * __init start_svm(void)
     P(cpu_has_svm_nrips, "Next-RIP Saved on #VMEXIT");
     P(cpu_has_svm_cleanbits, "VMCB Clean Bits");
     P(cpu_has_svm_decode, "DecodeAssists");
+    P(cpu_has_svm_vgif, "Virtual GIF");
     P(cpu_has_pause_filter, "Pause-Intercept Filter");
     P(cpu_has_tsc_ratio, "TSC Rate MSR");
 #undef P
diff --git a/xen/arch/x86/hvm/svm/vmcb.c b/xen/arch/x86/hvm/svm/vmcb.c
index 997e7597e0..ce656dcbce 100644
--- a/xen/arch/x86/hvm/svm/vmcb.c
+++ b/xen/arch/x86/hvm/svm/vmcb.c
@@ -206,6 +206,18 @@ static int construct_vmcb(struct vcpu *v)
         vmcb->_exception_intercepts |= (1U << TRAP_page_fault);
     }
 
+    /* if available, enable and configure virtual gif */
+    if ( cpu_has_svm_vgif )
+    {
+        vmcb->_vintr.fields.vgif = 1;
+        vmcb->_vintr.fields.vgif_enable = 1;
+        vmcb->_general2_intercepts &= ~GENERAL2_INTERCEPT_STGI;
+        vmcb->_general2_intercepts &= ~GENERAL2_INTERCEPT_CLGI;
+    }
+    else {
+        vmcb->_vintr.fields.vgif_enable = 0;
+    }
+
     if ( cpu_has_pause_filter )
     {
         vmcb->_pause_filter_count = SVM_PAUSEFILTER_INIT;
-- 
2.11.0


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Re: [PATCH v2 1/2] x86/svm: Add virtual GIF feature definition

[Konrad Rzeszutek Wilk]

On Thu, Nov 16, 2017 at 11:19:38AM -0600, Brian Woods wrote:
> Add support for enabling the virtual GIF feature.
> 
> Signed-off-by: Brian Woods <brian.woods@amd.com>
> ---
>  xen/include/asm-x86/hvm/svm/svm.h  | 2 ++
>  xen/include/asm-x86/hvm/svm/vmcb.h | 6 ++++--
>  2 files changed, 6 insertions(+), 2 deletions(-)

The patch says 'v2', but I don't see anything having changed here.

Usually one adds comments in here (right after ---) with something
to the effect of:

v1: New version
v2: Nothing new.

Or if something did change (like in second patch), you say exactly what changed.

Thanks!
> 
> diff --git a/xen/include/asm-x86/hvm/svm/svm.h b/xen/include/asm-x86/hvm/svm/svm.h
> index 0956f860ef..ec1eda6a3e 100644
> --- a/xen/include/asm-x86/hvm/svm/svm.h
> +++ b/xen/include/asm-x86/hvm/svm/svm.h
> @@ -64,6 +64,7 @@ extern u32 svm_feature_flags;
>  #define SVM_FEATURE_FLUSHBYASID    6 /* TLB flush by ASID support */
>  #define SVM_FEATURE_DECODEASSISTS  7 /* Decode assists support */
>  #define SVM_FEATURE_PAUSEFILTER   10 /* Pause intercept filter support */
> +#define SVM_FEATURE_VGIF          16 /* Virtual GIF */
>  
>  #define cpu_has_svm_feature(f) test_bit(f, &svm_feature_flags)
>  #define cpu_has_svm_npt       cpu_has_svm_feature(SVM_FEATURE_NPT)
> @@ -72,6 +73,7 @@ extern u32 svm_feature_flags;
>  #define cpu_has_svm_nrips     cpu_has_svm_feature(SVM_FEATURE_NRIPS)
>  #define cpu_has_svm_cleanbits cpu_has_svm_feature(SVM_FEATURE_VMCBCLEAN)
>  #define cpu_has_svm_decode    cpu_has_svm_feature(SVM_FEATURE_DECODEASSISTS)
> +#define cpu_has_svm_vgif      cpu_has_svm_feature(SVM_FEATURE_VGIF)
>  #define cpu_has_pause_filter  cpu_has_svm_feature(SVM_FEATURE_PAUSEFILTER)
>  #define cpu_has_tsc_ratio     cpu_has_svm_feature(SVM_FEATURE_TSCRATEMSR)
>  
> diff --git a/xen/include/asm-x86/hvm/svm/vmcb.h b/xen/include/asm-x86/hvm/svm/vmcb.h
> index 01ce20b0bd..595cfcf57b 100644
> --- a/xen/include/asm-x86/hvm/svm/vmcb.h
> +++ b/xen/include/asm-x86/hvm/svm/vmcb.h
> @@ -325,12 +325,14 @@ typedef union
>      {
>          u64 tpr:          8;
>          u64 irq:          1;
> -        u64 rsvd0:        7;
> +        u64 vgif:         1;
> +        u64 rsvd0:        6;
>          u64 prio:         4;
>          u64 ign_tpr:      1;
>          u64 rsvd1:        3;
>          u64 intr_masking: 1;
> -        u64 rsvd2:        7;
> +        u64 vgif_enable:  1;
> +        u64 rsvd2:        6;
>          u64 vector:       8;
>          u64 rsvd3:       24;
>      } fields;
> -- 
> 2.11.0
> 
> 
> _______________________________________________
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> https://lists.xen.org/xen-devel

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Re: [PATCH v2 1/2] x86/svm: Add virtual GIF feature definition

[Brian Woods]

On Thu, Nov 16, 2017 at 12:44:27PM -0500, Konrad Rzeszutek Wilk wrote:
> The patch says 'v2', but I don't see anything having changed here.
> 
> Usually one adds comments in here (right after ---) with something
> to the effect of:
> 
> v1: New version
> v2: Nothing new.
> 
> Or if something did change (like in second patch), you say exactly what changed.
> 
> Thanks!

Sorry about forgetting that.  I'll make sure to do that in the future.

The change log for this one was:
 - Change the test condition from if it had the vgif feature to if it's
   enabled in the vmcb
 - Update for the use of C99 bool type

There was some discussion in the irc channel so I'm not sure if there's
going be another version soon or not.  I need to fix the style error I
have with the else anyway.

Thank you for the feedback.

-- 
Brian Woods

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Re: [PATCH v2 0/2] Virtual GIF

[Boris Ostrovsky]

On 11/16/2017 12:19 PM, Brian Woods wrote:
> On AMD family 17h processors, there is a feature called virtual GIF.
> This allows a nested hypervisor to preform a CLGI or STGI without
> needing to be intercepted by the host hypervisor.  For more information
> about it please see:
>
> AMD64 Architecture Programmer’s Manual Volume 2: System Programming
> http://support.amd.com/TechDocs/24593.pdf
> Section: Virtual GIF (Section 15.33.2)
>
> This patch series adds support to check for and enable the virtual
> GIF features if available.
>
> These patches were tested on a AMD family 17h (EPYC 7401) system.
>
> Brian Woods (2):
>   x86/svm: Add virtual GIF feature definition
>   x86/svm: Add virtual GIF support
>
>  xen/arch/x86/hvm/svm/nestedsvm.c   |  7 ++++++-
>  xen/arch/x86/hvm/svm/svm.c         |  1 +
>  xen/arch/x86/hvm/svm/vmcb.c        | 12 ++++++++++++
>  xen/include/asm-x86/hvm/svm/svm.h  |  2 ++
>  xen/include/asm-x86/hvm/svm/vmcb.h |  6 ++++--
>  5 files changed, 25 insertions(+), 3 deletions(-)
>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

(with or without 'else' style changes in the second patch)

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