Re: [Xen-devel] [V5 4/4] libxc: expose xsaves/xgetbv1/xsavec to hvm guest

[Jan Beulich]

>>> On 21.09.15 at 13:34,  wrote:
> @@ -255,8 +260,9 @@ static void xc_cpuid_config_xsave(
>  regs[0] = regs[1] = regs[2] = regs[3] = 0;
>  break;
>  }
> -/* Don't touch EAX, EBX. Also cleanup ECX and EDX */
> -regs[2] = regs[3] = 0;
> +/* Don't touch EAX, EBX. Also cleanup EDX. Cleanup bits 01-32 of 
> ECX*/

This comment is off by one, and it will become stale the moment
XSS_SUPPORT gets added to. Better to write this in a more
generic way.

Jan

> +regs[2] &= XSS_SUPPORT;
> +regs[3] = 0;
>  break;
>  }
>  }



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[Xen-devel] [V5 4/4] libxc: expose xsaves/xgetbv1/xsavec to hvm guest

[Shuai Ruan]

This patch exposes xsaves/xgetbv1/xsavec to hvm guest.
The reserved bits of eax/ebx/ecx/edx must be cleaned up
when call cpuid(0dh) with leaf 1 or 2..63.

According to the spec the following bits must be reserved:
For leaf 1, bits 03-04/08-31 of ecx is reserved. Edx is reserved.
For leaf 2...63, bits 01-31 of ecx is reserved. Edx is reserved.

Acked-by: Ian Campbell 
Signed-off-by: Shuai Ruan 
---
 tools/libxc/xc_cpuid_x86.c | 14 ++
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index e146a3e..538d356 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -210,6 +210,10 @@ static void intel_xc_cpuid_policy(
 }
 
 #define XSAVEOPT(1 << 0)
+#define XSAVEC  (1 << 1)
+#define XGETBV1 (1 << 2)
+#define XSAVES  (1 << 3)
+#define XSS_SUPPORT (1 << 0)
 /* Configure extended state enumeration leaves (0x000D for xsave) */
 static void xc_cpuid_config_xsave(
 xc_interface *xch, domid_t domid, uint64_t xfeature_mask,
@@ -246,8 +250,9 @@ static void xc_cpuid_config_xsave(
 regs[1] = 512 + 64; /* FP/SSE + XSAVE.HEADER */
 break;
 case 1: /* leaf 1 */
-regs[0] &= XSAVEOPT;
-regs[1] = regs[2] = regs[3] = 0;
+regs[0] &= (XSAVEOPT | XSAVEC | XGETBV1 | XSAVES);
+regs[2] &= xfeature_mask;
+regs[3] = 0;
 break;
 case 2 ... 63: /* sub-leaves */
 if ( !(xfeature_mask & (1ULL << input[1])) )
@@ -255,8 +260,9 @@ static void xc_cpuid_config_xsave(
 regs[0] = regs[1] = regs[2] = regs[3] = 0;
 break;
 }
-/* Don't touch EAX, EBX. Also cleanup ECX and EDX */
-regs[2] = regs[3] = 0;
+/* Don't touch EAX, EBX. Also cleanup EDX. Cleanup bits 01-32 of ECX*/
+regs[2] &= XSS_SUPPORT;
+regs[3] = 0;
 break;
 }
 }
-- 
1.9.1


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