Hello tech@,
The following diff should expose TSC to guest vm and OpenBSD guests
should be able to choose tsc as a preferred timecounter if the host
machine is >= skylake.
This should improve the guest clock drift situation significantly.
I am aware that this breaks received vms and am working on handling
that.
Thanks,
Pratik
Index: sys/arch/amd64/amd64/vmm.c
===================================================================
RCS file: /home/pdvyas/cvs/src/sys/arch/amd64/amd64/vmm.c,v
retrieving revision 1.157
diff -u -p -a -u -r1.157 vmm.c
--- sys/arch/amd64/amd64/vmm.c 2 Jul 2017 19:49:31 -0000 1.157
+++ sys/arch/amd64/amd64/vmm.c 23 Jul 2017 03:49:30 -0000
@@ -5200,7 +5200,7 @@ vmm_handle_cpuid(struct vcpu *vcpu)
switch (*rax) {
case 0x00: /* Max level and vendor ID */
- *rax = 0x0d; /* cpuid_level */
+ *rax = cpuid_level;
*rbx = *((uint32_t *)&cpu_vendor);
*rdx = *((uint32_t *)&cpu_vendor + 1);
*rcx = *((uint32_t *)&cpu_vendor + 2);
@@ -5226,7 +5226,6 @@ vmm_handle_cpuid(struct vcpu *vcpu)
* direct cache access (CPUIDECX_DCA)
* x2APIC (CPUIDECX_X2APIC)
* apic deadline (CPUIDECX_DEADLINE)
- * timestamp (CPUID_TSC)
* apic (CPUID_APIC)
* psn (CPUID_PSN)
* self snoop (CPUID_SS)
@@ -5243,10 +5242,9 @@ vmm_handle_cpuid(struct vcpu *vcpu)
CPUIDECX_SDBG | CPUIDECX_XTPR | CPUIDECX_PCID |
CPUIDECX_DCA | CPUIDECX_X2APIC | CPUIDECX_DEADLINE);
*rdx = curcpu()->ci_feature_flags &
- ~(CPUID_ACPI | CPUID_TM | CPUID_TSC |
- CPUID_HTT | CPUID_DS | CPUID_APIC |
- CPUID_PSN | CPUID_SS | CPUID_PBE |
- CPUID_MTRR);
+ ~(CPUID_ACPI | CPUID_TM | CPUID_HTT |
+ CPUID_DS | CPUID_APIC | CPUID_PSN |
+ CPUID_SS | CPUID_PBE | CPUID_MTRR);
break;
case 0x02: /* Cache and TLB information */
*rax = eax;
@@ -5399,13 +5397,8 @@ vmm_handle_cpuid(struct vcpu *vcpu)
*rcx = 0;
*rdx = 0;
break;
- case 0x15: /* TSC / Core Crystal Clock info (not supported) */
- DPRINTF("%s: function 0x15 (TSC / CCC info) not supported\n",
- __func__);
- *rax = 0;
- *rbx = 0;
- *rcx = 0;
- *rdx = 0;
+ case 0x15:
+ CPUID(0x15, *rax, *rbx, *rcx, *rdx);
break;
case 0x16: /* Processor frequency info (not supported) */
DPRINTF("%s: function 0x16 (frequency info) not supported\n",
@@ -5432,7 +5425,6 @@ vmm_handle_cpuid(struct vcpu *vcpu)
*rbx = 0; /* Reserved */
*rcx = curcpu()->ci_efeature_ecx;
*rdx = curcpu()->ci_feature_eflags;
- *rdx &= ~CPUID_RDTSCP;
break;
case 0x80000002: /* Brand string */
*rax = curcpu()->ci_brand[0];
@@ -5465,10 +5457,7 @@ vmm_handle_cpuid(struct vcpu *vcpu)
*rdx = curcpu()->ci_extcacheinfo[3];
break;
case 0x80000007: /* apmi */
- *rax = 0; /* Reserved */
- *rbx = 0; /* Reserved */
- *rcx = 0; /* Reserved */
- *rdx = 0; /* unsupported ITSC */
+ CPUID(0x80000007, *rax, *rbx, *rcx, *rdx);
break;
case 0x80000008: /* Phys bits info and topology (AMD) */
DPRINTF("%s: function 0x80000008 (phys bits info) not "
