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[Xen-devel] [PATCH RFC 14/31] tools/libxc: Use featureset rather than guesswork



It is conceptually wrong to base a VM's featureset on the features visible to
the toolstack which happens to construct it.

Instead, the featureset used is either an explicit one passed by the
toolstack, or the default which Xen believes it can give to the guest.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxc/xc_cpuid_x86.c | 229 +++++++++++++--------------------------------
 1 file changed, 64 insertions(+), 165 deletions(-)

diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index 8bd3126..3f39306 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -24,6 +24,7 @@
 #include "xc_private.h"
 #include <xen/arch-x86/featureset.h>
 #include <xen/hvm/params.h>
+#include <xen/sysctl.h>
 
 #define bitmaskof(idx)      (1u << ((idx) & 31))
 #define clear_bit(idx, dst) ((dst) &= ~bitmaskof(idx))
@@ -211,37 +212,19 @@ static void amd_xc_cpuid_policy(xc_interface *xch,
             regs[0] = DEF_MAX_AMDEXT;
         break;
 
-    case 0x80000001: {
+    case 0x80000001:
         if ( !info->pae )
             clear_bit(X86_FEATURE_PAE, regs[3]);
 
-        /* Filter all other features according to a whitelist. */
-        regs[2] &= (bitmaskof(X86_FEATURE_LAHF_LM) |
-                    bitmaskof(X86_FEATURE_CMP_LEGACY) |
-                    (info->nestedhvm ? bitmaskof(X86_FEATURE_SVM) : 0) |
-                    bitmaskof(X86_FEATURE_CR8_LEGACY) |
-                    bitmaskof(X86_FEATURE_ABM) |
-                    bitmaskof(X86_FEATURE_SSE4A) |
-                    bitmaskof(X86_FEATURE_MISALIGNSSE) |
-                    bitmaskof(X86_FEATURE_3DNOWPREFETCH) |
-                    bitmaskof(X86_FEATURE_OSVW) |
-                    bitmaskof(X86_FEATURE_XOP) |
-                    bitmaskof(X86_FEATURE_LWP) |
-                    bitmaskof(X86_FEATURE_FMA4) |
-                    bitmaskof(X86_FEATURE_TBM) |
-                    bitmaskof(X86_FEATURE_DBEXT));
-        regs[3] &= (0x0183f3ff | /* features shared with 0x00000001:EDX */
-                    bitmaskof(X86_FEATURE_NX) |
-                    bitmaskof(X86_FEATURE_LM) |
-                    bitmaskof(X86_FEATURE_PAGE1GB) |
-                    bitmaskof(X86_FEATURE_SYSCALL) |
-                    bitmaskof(X86_FEATURE_MP) |
-                    bitmaskof(X86_FEATURE_MMXEXT) |
-                    bitmaskof(X86_FEATURE_FFXSR) |
-                    bitmaskof(X86_FEATURE_3DNOW) |
-                    bitmaskof(X86_FEATURE_3DNOWEXT));
+        if ( !info->nestedhvm )
+            clear_bit(X86_FEATURE_SVM, regs[2]);
+
+        if ( info->xfeature_mask == 0 )
+        {
+            clear_bit(X86_FEATURE_FMA4, regs[2]);
+            clear_bit(X86_FEATURE_LWP, regs[2]);
+        }
         break;
-    }
 
     case 0x80000008:
         /*
@@ -290,9 +273,8 @@ static void intel_xc_cpuid_policy(xc_interface *xch,
     switch ( input[0] )
     {
     case 0x00000001:
-        /* ECX[5] is availability of VMX */
-        if ( info->nestedhvm )
-            set_bit(X86_FEATURE_VMXE, regs[2]);
+        if ( !info->nestedhvm )
+            clear_bit(X86_FEATURE_VMXE, regs[2]);
         break;
 
     case 0x00000004:
@@ -310,19 +292,6 @@ static void intel_xc_cpuid_policy(xc_interface *xch,
             regs[0] = DEF_MAX_INTELEXT;
         break;
 
-    case 0x80000001: {
-        /* Only a few features are advertised in Intel's 0x80000001. */
-        regs[2] &= (bitmaskof(X86_FEATURE_LAHF_LM) |
-                    bitmaskof(X86_FEATURE_3DNOWPREFETCH) |
-                    bitmaskof(X86_FEATURE_ABM));
-        regs[3] &= (bitmaskof(X86_FEATURE_NX) |
-                    bitmaskof(X86_FEATURE_LM) |
-                    bitmaskof(X86_FEATURE_PAGE1GB) |
-                    bitmaskof(X86_FEATURE_SYSCALL) |
-                    bitmaskof(X86_FEATURE_RDTSCP));
-        break;
-    }
-
     case 0x80000005:
         regs[0] = regs[1] = regs[2] = 0;
         break;
@@ -371,7 +340,7 @@ static void xc_cpuid_config_xsave(xc_interface *xch,
         regs[1] = 512 + 64; /* FP/SSE + XSAVE.HEADER */
         break;
     case 1: /* leaf 1 */
-        regs[0] &= XSAVEOPT;
+        regs[0] = info->featureset[XEN_FEATURESET_Da1];
         regs[1] = regs[2] = regs[3] = 0;
         break;
     case 2 ... 63: /* sub-leaves */
@@ -404,53 +373,16 @@ static void xc_cpuid_hvm_policy(xc_interface *xch,
          */
         regs[1] = (regs[1] & 0x0000ffffu) | ((regs[1] & 0x007f0000u) << 1);
 
-        regs[2] &= (bitmaskof(X86_FEATURE_XMM3) |
-                    bitmaskof(X86_FEATURE_PCLMULQDQ) |
-                    bitmaskof(X86_FEATURE_SSSE3) |
-                    bitmaskof(X86_FEATURE_FMA) |
-                    bitmaskof(X86_FEATURE_CX16) |
-                    bitmaskof(X86_FEATURE_PCID) |
-                    bitmaskof(X86_FEATURE_SSE4_1) |
-                    bitmaskof(X86_FEATURE_SSE4_2) |
-                    bitmaskof(X86_FEATURE_MOVBE)  |
-                    bitmaskof(X86_FEATURE_POPCNT) |
-                    bitmaskof(X86_FEATURE_AES) |
-                    bitmaskof(X86_FEATURE_F16C) |
-                    bitmaskof(X86_FEATURE_RDRAND) |
-                    ((info->xfeature_mask != 0) ?
-                     (bitmaskof(X86_FEATURE_AVX) |
-                      bitmaskof(X86_FEATURE_XSAVE)) : 0));
-
-        regs[2] |= (bitmaskof(X86_FEATURE_HYPERVISOR) |
-                    bitmaskof(X86_FEATURE_TSC_DEADLINE) |
-                    bitmaskof(X86_FEATURE_X2APIC));
-
-        regs[3] &= (bitmaskof(X86_FEATURE_FPU) |
-                    bitmaskof(X86_FEATURE_VME) |
-                    bitmaskof(X86_FEATURE_DE) |
-                    bitmaskof(X86_FEATURE_PSE) |
-                    bitmaskof(X86_FEATURE_TSC) |
-                    bitmaskof(X86_FEATURE_MSR) |
-                    bitmaskof(X86_FEATURE_PAE) |
-                    bitmaskof(X86_FEATURE_MCE) |
-                    bitmaskof(X86_FEATURE_CX8) |
-                    bitmaskof(X86_FEATURE_APIC) |
-                    bitmaskof(X86_FEATURE_SEP) |
-                    bitmaskof(X86_FEATURE_MTRR) |
-                    bitmaskof(X86_FEATURE_PGE) |
-                    bitmaskof(X86_FEATURE_MCA) |
-                    bitmaskof(X86_FEATURE_CMOV) |
-                    bitmaskof(X86_FEATURE_PAT) |
-                    bitmaskof(X86_FEATURE_CLFLSH) |
-                    bitmaskof(X86_FEATURE_PSE36) |
-                    bitmaskof(X86_FEATURE_MMX) |
-                    bitmaskof(X86_FEATURE_FXSR) |
-                    bitmaskof(X86_FEATURE_XMM) |
-                    bitmaskof(X86_FEATURE_XMM2) |
-                    bitmaskof(X86_FEATURE_HT));
-            
-        /* We always support MTRR MSRs. */
-        regs[3] |= bitmaskof(X86_FEATURE_MTRR);
+        regs[2] = info->featureset[XEN_FEATURESET_1c];
+        regs[3] = info->featureset[XEN_FEATURESET_1d];
+
+        if ( info->xfeature_mask == 0 )
+        {
+            clear_bit(X86_FEATURE_AVX, regs[2]);
+            clear_bit(X86_FEATURE_F16C, regs[2]);
+            clear_bit(X86_FEATURE_FMA, regs[2]);
+            clear_bit(X86_FEATURE_XSAVE, regs[2]);
+        }
 
         if ( !info->pae )
         {
@@ -460,23 +392,17 @@ static void xc_cpuid_hvm_policy(xc_interface *xch,
         break;
 
     case 0x00000007: /* Intel-defined CPU features */
-        if ( input[1] == 0 ) {
-            regs[1] &= (bitmaskof(X86_FEATURE_TSC_ADJUST) |
-                        bitmaskof(X86_FEATURE_BMI1) |
-                        bitmaskof(X86_FEATURE_HLE)  |
-                        bitmaskof(X86_FEATURE_AVX2) |
-                        bitmaskof(X86_FEATURE_SMEP) |
-                        bitmaskof(X86_FEATURE_BMI2) |
-                        bitmaskof(X86_FEATURE_ERMS) |
-                        bitmaskof(X86_FEATURE_INVPCID) |
-                        bitmaskof(X86_FEATURE_RTM)  |
-                        bitmaskof(X86_FEATURE_RDSEED)  |
-                        bitmaskof(X86_FEATURE_ADX)  |
-                        bitmaskof(X86_FEATURE_SMAP) |
-                        bitmaskof(X86_FEATURE_FSGSBASE));
-        } else
+        if ( input[1] == 0 )
+        {
+            regs[1] = info->featureset[XEN_FEATURESET_7b0];
+            regs[2] = info->featureset[XEN_FEATURESET_7c0];
+        }
+        else
+        {
             regs[1] = 0;
-        regs[0] = regs[2] = regs[3] = 0;
+            regs[2] = 0;
+        }
+        regs[0] = regs[3] = 0;
         break;
 
     case 0x0000000d:
@@ -488,6 +414,9 @@ static void xc_cpuid_hvm_policy(xc_interface *xch,
         break;
 
     case 0x80000001:
+        regs[2] = info->featureset[XEN_FEATURESET_e1c];
+        regs[3] = info->featureset[XEN_FEATURESET_e1d];
+
         if ( !info->pae )
         {
             clear_bit(X86_FEATURE_LAHF_LM, regs[2]);
@@ -539,64 +468,42 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
                                const struct cpuid_domain_info *info,
                                const unsigned int *input, unsigned int *regs)
 {
-    if ( (input[0] & 0x7fffffff) == 0x00000001 )
-    {
-        clear_bit(X86_FEATURE_VME, regs[3]);
-        if ( !info->pvh )
-        {
-            clear_bit(X86_FEATURE_PSE, regs[3]);
-            clear_bit(X86_FEATURE_PGE, regs[3]);
-        }
-        clear_bit(X86_FEATURE_MCE, regs[3]);
-        clear_bit(X86_FEATURE_MCA, regs[3]);
-        clear_bit(X86_FEATURE_MTRR, regs[3]);
-        clear_bit(X86_FEATURE_PSE36, regs[3]);
-    }
-
     switch ( input[0] )
     {
     case 0x00000001:
-        if ( info->vendor == VENDOR_AMD )
-            clear_bit(X86_FEATURE_SEP, regs[3]);
-        clear_bit(X86_FEATURE_DS, regs[3]);
-        clear_bit(X86_FEATURE_ACC, regs[3]);
-        clear_bit(X86_FEATURE_PBE, regs[3]);
-
-        clear_bit(X86_FEATURE_DTES64, regs[2]);
-        clear_bit(X86_FEATURE_MWAIT, regs[2]);
-        clear_bit(X86_FEATURE_DSCPL, regs[2]);
-        clear_bit(X86_FEATURE_VMXE, regs[2]);
-        clear_bit(X86_FEATURE_SMXE, regs[2]);
-        clear_bit(X86_FEATURE_EST, regs[2]);
-        clear_bit(X86_FEATURE_TM2, regs[2]);
+        regs[2] = info->featureset[XEN_FEATURESET_1c];
+        regs[3] = info->featureset[XEN_FEATURESET_1d];
+
         if ( !info->pv64 )
             clear_bit(X86_FEATURE_CX16, regs[2]);
+
         if ( info->xfeature_mask == 0 )
         {
             clear_bit(X86_FEATURE_XSAVE, regs[2]);
             clear_bit(X86_FEATURE_AVX, regs[2]);
+            clear_bit(X86_FEATURE_F16C, regs[2]);
+            clear_bit(X86_FEATURE_FMA, regs[2]);
+        }
+
+        if ( !info->pvh )
+        {
+            clear_bit(X86_FEATURE_PSE, regs[3]);
+            clear_bit(X86_FEATURE_PGE, regs[3]);
         }
-        clear_bit(X86_FEATURE_XTPR, regs[2]);
-        clear_bit(X86_FEATURE_PDCM, regs[2]);
-        clear_bit(X86_FEATURE_PCID, regs[2]);
-        clear_bit(X86_FEATURE_DCA, regs[2]);
-        set_bit(X86_FEATURE_HYPERVISOR, regs[2]);
         break;
 
     case 0x00000007:
         if ( input[1] == 0 )
-            regs[1] &= (bitmaskof(X86_FEATURE_BMI1) |
-                        bitmaskof(X86_FEATURE_HLE)  |
-                        bitmaskof(X86_FEATURE_AVX2) |
-                        bitmaskof(X86_FEATURE_BMI2) |
-                        bitmaskof(X86_FEATURE_ERMS) |
-                        bitmaskof(X86_FEATURE_RTM)  |
-                        bitmaskof(X86_FEATURE_RDSEED)  |
-                        bitmaskof(X86_FEATURE_ADX)  |
-                        bitmaskof(X86_FEATURE_FSGSBASE));
+        {
+            regs[1] = info->featureset[XEN_FEATURESET_7b0];
+            regs[2] = info->featureset[XEN_FEATURESET_7c0];
+        }
         else
+        {
             regs[1] = 0;
-        regs[0] = regs[2] = regs[3] = 0;
+            regs[2] = 0;
+        }
+        regs[0] = regs[3] = 0;
         break;
 
     case 0x0000000d:
@@ -604,29 +511,21 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
         break;
 
     case 0x80000001:
+        regs[2] = info->featureset[XEN_FEATURESET_e1c];
+        regs[3] = info->featureset[XEN_FEATURESET_e1d];
+
         if ( !info->pv64 )
         {
             clear_bit(X86_FEATURE_LM, regs[3]);
             clear_bit(X86_FEATURE_LAHF_LM, regs[2]);
-            if ( info->vendor != VENDOR_AMD )
-                clear_bit(X86_FEATURE_SYSCALL, regs[3]);
-        }
-        else
-        {
-            set_bit(X86_FEATURE_SYSCALL, regs[3]);
         }
+
         if ( !info->pvh )
+        {
+            clear_bit(X86_FEATURE_PSE, regs[3]);
+            clear_bit(X86_FEATURE_PGE, regs[3]);
             clear_bit(X86_FEATURE_PAGE1GB, regs[3]);
-        clear_bit(X86_FEATURE_RDTSCP, regs[3]);
-
-        clear_bit(X86_FEATURE_SVM, regs[2]);
-        clear_bit(X86_FEATURE_OSVW, regs[2]);
-        clear_bit(X86_FEATURE_IBS, regs[2]);
-        clear_bit(X86_FEATURE_SKINIT, regs[2]);
-        clear_bit(X86_FEATURE_WDT, regs[2]);
-        clear_bit(X86_FEATURE_LWP, regs[2]);
-        clear_bit(X86_FEATURE_NODEID_MSR, regs[2]);
-        clear_bit(X86_FEATURE_TOPOEXT, regs[2]);
+        }
         break;
 
     case 0x00000005: /* MONITOR/MWAIT */
-- 
2.1.4


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