[PATCH v3 13/22] x86: XFD enabling

[Jan Beulich <jbeulich@suse.com>]

Just like for XCR0 we generally want to run with the guest settings of
the involved MSRs while in Xen. Hence saving/restoring of guest values
needs to only happen during context switch.

While adding the feature to libxl's table I've noticed the other XSAVE
sub-features all don't have entries there. These get added at the same
time.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v3: New.
---
I wasn't sure whether we want to have AMX depend on XFD. Purely from a
spec pov the two are independent features (without XFD one simply
wouldn't have a way to disable it for the purpose of lazy allocation of
state saving space).

--- a/tools/libs/light/libxl_cpuid.c
+++ b/tools/libs/light/libxl_cpuid.c
@@ -237,6 +237,12 @@ int libxl_cpuid_parse_config(libxl_cpuid
         {"fsrs",         0x00000007,  1, CPUID_REG_EAX, 11,  1},
         {"fsrcs",        0x00000007,  1, CPUID_REG_EAX, 12,  1},
 
+        {"xsaveopt",     0x0000000d,  1, CPUID_REG_EAX,  0,  1},
+        {"xsavec",       0x0000000d,  1, CPUID_REG_EAX,  1,  1},
+        {"xgetbv1",      0x0000000d,  1, CPUID_REG_EAX,  2,  1},
+        {"xsaves",       0x0000000d,  1, CPUID_REG_EAX,  3,  1},
+        {"xfd",          0x0000000d,  1, CPUID_REG_EAX,  4,  1},
+
         {"lahfsahf",     0x80000001, NA, CPUID_REG_ECX,  0,  1},
         {"cmplegacy",    0x80000001, NA, CPUID_REG_ECX,  1,  1},
         {"svm",          0x80000001, NA, CPUID_REG_ECX,  2,  1},
--- a/tools/misc/xen-cpuid.c
+++ b/tools/misc/xen-cpuid.c
@@ -116,6 +116,7 @@ static const char *const str_Da1[32] =
 {
     [ 0] = "xsaveopt", [ 1] = "xsavec",
     [ 2] = "xgetbv1",  [ 3] = "xsaves",
+    [ 4] = "xfd",
 };
 
 static const char *const str_7c0[32] =
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -230,6 +230,7 @@ static void recalculate_xstate(struct cp
         p->xstate.comp[i].offset = xstate_offset(i);
         p->xstate.comp[i].xss    = curr_xstate & XSTATE_XSAVES_ONLY;
         p->xstate.comp[i].align  = curr_xstate & xstate_align;
+        p->xstate.comp[i].xfd    = curr_xstate & xfd_mask;
     }
 }
 
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1837,6 +1837,12 @@ void paravirt_ctxt_switch_to(struct vcpu
 
     if ( cpu_has_msr_tsc_aux )
         wrmsr_tsc_aux(v->arch.msrs->tsc_aux);
+
+    if ( v->domain->arch.cpuid->xstate.xfd )
+    {
+        wrmsrl(MSR_XFD, v->arch.msrs->xfd);
+        wrmsrl(MSR_XFD_ERR, v->arch.msrs->xfd_err);
+    }
 }
 
 /* Update per-VCPU guest runstate shared memory area (if registered). */
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -1101,6 +1101,8 @@ long arch_do_domctl(
         static const uint32_t msrs_to_send[] = {
             MSR_SPEC_CTRL,
             MSR_INTEL_MISC_FEATURES_ENABLES,
+            MSR_XFD,
+            MSR_XFD_ERR,
             MSR_TSC_AUX,
             MSR_AMD64_DR0_ADDRESS_MASK,
             MSR_AMD64_DR1_ADDRESS_MASK,
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1178,6 +1178,12 @@ static int construct_vmcs(struct vcpu *v
         if ( (vmexit_ctl & VM_EXIT_CLEAR_BNDCFGS) &&
              (vmentry_ctl & VM_ENTRY_LOAD_BNDCFGS) )
             vmx_clear_msr_intercept(v, MSR_IA32_BNDCFGS, VMX_MSR_RW);
+
+        if ( d->arch.cpuid->xstate.xfd )
+        {
+            vmx_clear_msr_intercept(v, MSR_XFD, VMX_MSR_RW);
+            vmx_clear_msr_intercept(v, MSR_XFD_ERR, VMX_MSR_RW);
+        }
     }
 
     /* I/O access bitmap. */
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -539,6 +539,12 @@ static void vmx_save_guest_msrs(struct v
      */
     v->arch.hvm.vmx.shadow_gs = read_gs_shadow();
 
+    if ( v->domain->arch.cpuid->xstate.xfd )
+    {
+        rdmsrl(MSR_XFD, msrs->xfd);
+        rdmsrl(MSR_XFD_ERR, msrs->xfd_err);
+    }
+
     if ( v->arch.hvm.vmx.ipt_active )
     {
         rdmsrl(MSR_RTIT_OUTPUT_MASK, msrs->rtit.output_mask);
@@ -558,6 +564,12 @@ static void vmx_restore_guest_msrs(struc
     if ( cpu_has_msr_tsc_aux )
         wrmsr_tsc_aux(msrs->tsc_aux);
 
+    if ( v->domain->arch.cpuid->xstate.xfd )
+    {
+        wrmsrl(MSR_XFD, msrs->xfd);
+        wrmsrl(MSR_XFD_ERR, msrs->xfd_err);
+    }
+
     if ( v->arch.hvm.vmx.ipt_active )
     {
         wrmsrl(MSR_RTIT_OUTPUT_BASE, page_to_maddr(v->vmtrace.pg));
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -29,6 +29,7 @@
 #include <asm/hvm/viridian.h>
 #include <asm/msr.h>
 #include <asm/setup.h>
+#include <asm/xstate.h>
 
 #include <public/hvm/params.h>
 
@@ -267,6 +268,18 @@ int guest_rdmsr(struct vcpu *v, uint32_t
         *val = msrs->misc_features_enables.raw;
         break;
 
+    case MSR_XFD:
+    case MSR_XFD_ERR:
+        if ( !cp->xstate.xfd )
+            goto gp_fault;
+        if ( v == curr && is_hvm_domain(d) )
+            rdmsrl(msr, *val);
+        else if ( msr == MSR_XFD )
+            *val = msrs->xfd;
+        else
+            *val = msrs->xfd_err;
+        break;
+
     case MSR_IA32_MCG_CAP     ... MSR_IA32_MCG_CTL:      /* 0x179 -> 0x17b */
     case MSR_IA32_MCx_CTL2(0) ... MSR_IA32_MCx_CTL2(31): /* 0x280 -> 0x29f */
     case MSR_IA32_MCx_CTL(0)  ... MSR_IA32_MCx_MISC(31): /* 0x400 -> 0x47f */
@@ -523,6 +536,19 @@ int guest_wrmsr(struct vcpu *v, uint32_t
         break;
     }
 
+    case MSR_XFD:
+    case MSR_XFD_ERR:
+        if ( !cp->xstate.xfd ||
+             (val & ~(cpuid_policy_xstates(cp) & xfd_mask)) )
+            goto gp_fault;
+        if ( v == curr )
+            wrmsrl(msr, val);
+        if ( msr == MSR_XFD )
+            msrs->xfd = val;
+        else
+            msrs->xfd_err = val;
+        break;
+
     case MSR_IA32_MCG_CAP     ... MSR_IA32_MCG_CTL:      /* 0x179 -> 0x17b */
     case MSR_IA32_MCx_CTL2(0) ... MSR_IA32_MCx_CTL2(31): /* 0x280 -> 0x29f */
     case MSR_IA32_MCx_CTL(0)  ... MSR_IA32_MCx_MISC(31): /* 0x400 -> 0x47f */
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -29,6 +29,10 @@
 u64 __read_mostly xfeature_mask;
 
 u64 __read_mostly xstate_align;
+
+/* Mask of XSAVE/XRSTOR features supporting XFD. */
+uint64_t __read_mostly xfd_mask;
+
 static unsigned int __read_mostly xstate_features;
 
 uint32_t __read_mostly mxcsr_mask = 0x0000ffbf;
@@ -106,6 +110,11 @@ static int setup_xstate_features(bool bs
             __set_bit(leaf, &xstate_align);
         else
             BUG_ON(!(ecx & XSTATE_ALIGN64) != !test_bit(leaf, &xstate_align));
+
+        if ( bsp && (ecx & XSTATE_XFD) )
+            __set_bit(leaf, &xfd_mask);
+        else
+            BUG_ON(!(ecx & XSTATE_XFD) != !test_bit(leaf, &xfd_mask));
     }
 
     return 0;
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -69,6 +69,10 @@
 #define MSR_MCU_OPT_CTRL                    0x00000123
 #define  MCU_OPT_CTRL_RNGDS_MITG_DIS        (_AC(1, ULL) <<  0)
 
+/* Bits within these two MSRs share positions with XCR0. */
+#define MSR_XFD                             0x000001c4
+#define MSR_XFD_ERR                         0x000001c5
+
 #define MSR_RTIT_OUTPUT_BASE                0x00000560
 #define MSR_RTIT_OUTPUT_MASK                0x00000561
 #define MSR_RTIT_CTL                        0x00000570
--- a/xen/include/asm-x86/msr.h
+++ b/xen/include/asm-x86/msr.h
@@ -343,6 +343,12 @@ struct vcpu_msrs
         uint64_t raw;
     } xss;
 
+    /* 0x000001c4 - MSR_XFD */
+    uint64_t xfd;
+
+    /* 0x000001c5 - MSR_XFD_ERR */
+    uint64_t xfd_err;
+
     /*
      * 0xc0000103 - MSR_TSC_AUX
      *
--- a/xen/include/asm-x86/xstate.h
+++ b/xen/include/asm-x86/xstate.h
@@ -39,9 +39,11 @@ extern uint32_t mxcsr_mask;
 #define XSTATE_COMPACTION_ENABLED  (1ULL << 63)
 
 #define XSTATE_ALIGN64 (1U << 1)
+#define XSTATE_XFD     (1U << 2)
 
 extern u64 xfeature_mask;
 extern u64 xstate_align;
+extern uint64_t xfd_mask;
 
 #define xstate_offset(n) (raw_cpuid_policy.xstate.comp[n].offset)
 #define xstate_size(n)   (raw_cpuid_policy.xstate.comp[n].size)
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -191,6 +191,7 @@ XEN_CPUFEATURE(XSAVEOPT,      4*32+ 0) /
 XEN_CPUFEATURE(XSAVEC,        4*32+ 1) /*A  XSAVEC/XRSTORC instructions */
 XEN_CPUFEATURE(XGETBV1,       4*32+ 2) /*A  XGETBV with %ecx=1 */
 XEN_CPUFEATURE(XSAVES,        4*32+ 3) /*S  XSAVES/XRSTORS instructions */
+XEN_CPUFEATURE(XFD,           4*32+ 4) /*   XFD / XFD_ERR MSRs */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:0.ebx, word 5 */
 XEN_CPUFEATURE(FSGSBASE,      5*32+ 0) /*A  {RD,WR}{FS,GS}BASE instructions */
--- a/xen/include/xen/lib/x86/cpuid.h
+++ b/xen/include/xen/lib/x86/cpuid.h
@@ -222,7 +222,7 @@ struct cpuid_policy
         /* Per-component common state.  Valid for i >= 2. */
         struct {
             uint32_t size, offset;
-            bool xss:1, align:1;
+            bool xss:1, align:1, xfd:1;
             uint32_t _res_d;
         } comp[CPUID_GUEST_NR_XSTATE];
     } xstate;
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -221,7 +221,7 @@ def crunch_numbers(state):
         # are instructions built on top of base XSAVE, while others are new
         # instruction groups which are specified to require XSAVE for state
         # management.
-        XSAVE: [XSAVEOPT, XSAVEC, XGETBV1, XSAVES,
+        XSAVE: [XSAVEOPT, XSAVEC, XGETBV1, XSAVES, XFD,
                 AVX, MPX, PKU, AMX_TILE, LWP],
 
         # AVX is taken to mean hardware support for 256bit registers (which in