[Xen-devel] [V6 4/4] libxc: expose xsaves/xgetbv1/xsavec to hvm guest

[Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>]

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 <ian.campbell@xxxxxxxxxx>
Signed-off-by: Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>
---
 tools/libxc/xc_cpuid_x86.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index e146a3e..b0d6ecc 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 (0x0000000D 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 +260,11 @@ 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 and cleanup EDX.
+         * Bit 0 of ECX represent whether sub-leave is supported in IA32_XSS
+         * msr or supported in XCR0.*/
+        regs[2] &= XSS_SUPPORT;
+        regs[3] = 0;
         break;
     }
 }
-- 
1.9.1


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