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KVM: x86: Add support for VMware backdoor Pseudo-PMCs

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VMware exposes the following Pseudo PMCs:
0x10000: Physical host TSC
0x10001: Elapsed real time in ns
0x10002: Elapsed apparent time in ns

For more info refer to:
https://www.vmware.com/files/pdf/techpaper/Timekeeping-In-VirtualMachines.pdf

VMware allows access to these Pseduo-PMCs even when read via RDPMC
in Ring3 and CR4.PCE=0. Therefore, commit modifies x86 emulator
to allow access to these PMCs in this situation. In addition,
emulation of these PMCs were added to kvm_pmu_rdpmc().

Signed-off-by: Arbel Moshe <arbel.moshe@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Arbel Moshe 2018-03-12 13:12:53 +02:00 committed by Paolo Bonzini
parent 9718420e9f
commit 2d7921c499
4 changed files with 75 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/kvm/emulate.c
View File

@ -30,6 +30,7 @@
#include "x86.h"
#include "tss.h"
#include "mmu.h"
#include "pmu.h"
/*
* Operand types
@ -4293,6 +4294,13 @@ static int check_rdpmc(struct x86_emulate_ctxt *ctxt)
u64 cr4 = ctxt->ops->get_cr(ctxt, 4);
u64 rcx = reg_read(ctxt, VCPU_REGS_RCX);
/*
* VMware allows access to these Pseduo-PMCs even when read via RDPMC
* in Ring3 when CR4.PCE=0.
*/
if (enable_vmware_backdoor && is_vmware_backdoor_pmc(rcx))
return X86EMUL_CONTINUE;
if ((!(cr4 & X86_CR4_PCE) && ctxt->ops->cpl(ctxt)) ||
ctxt->ops->check_pmc(ctxt, rcx))
return emulate_gp(ctxt, 0);

37
arch/x86/kvm/pmu.c
View File

@ -244,12 +244,49 @@ int kvm_pmu_is_valid_msr_idx(struct kvm_vcpu *vcpu, unsigned idx)
return kvm_x86_ops->pmu_ops->is_valid_msr_idx(vcpu, idx);
}
bool is_vmware_backdoor_pmc(u32 pmc_idx)
{
switch (pmc_idx) {
case VMWARE_BACKDOOR_PMC_HOST_TSC:
case VMWARE_BACKDOOR_PMC_REAL_TIME:
case VMWARE_BACKDOOR_PMC_APPARENT_TIME:
return true;
}
return false;
}
static int kvm_pmu_rdpmc_vmware(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
{
u64 ctr_val;
switch (idx) {
case VMWARE_BACKDOOR_PMC_HOST_TSC:
ctr_val = rdtsc();
break;
case VMWARE_BACKDOOR_PMC_REAL_TIME:
ctr_val = ktime_get_boot_ns();
break;
case VMWARE_BACKDOOR_PMC_APPARENT_TIME:
ctr_val = ktime_get_boot_ns() +
vcpu->kvm->arch.kvmclock_offset;
break;
default:
return 1;
}
*data = ctr_val;
return 0;
}
int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
{
bool fast_mode = idx & (1u << 31);
struct kvm_pmc *pmc;
u64 ctr_val;
if (is_vmware_backdoor_pmc(idx))
return kvm_pmu_rdpmc_vmware(vcpu, idx, data);
pmc = kvm_x86_ops->pmu_ops->msr_idx_to_pmc(vcpu, idx);
if (!pmc)
return 1;

6
arch/x86/kvm/pmu.h
View File

@ -9,6 +9,10 @@
/* retrieve the 4 bits for EN and PMI out of IA32_FIXED_CTR_CTRL */
#define fixed_ctrl_field(ctrl_reg, idx) (((ctrl_reg) >> ((idx)*4)) & 0xf)
#define VMWARE_BACKDOOR_PMC_HOST_TSC 0x10000
#define VMWARE_BACKDOOR_PMC_REAL_TIME 0x10001
#define VMWARE_BACKDOOR_PMC_APPARENT_TIME 0x10002
struct kvm_event_hw_type_mapping {
u8 eventsel;
u8 unit_mask;
@ -114,6 +118,8 @@ void kvm_pmu_reset(struct kvm_vcpu *vcpu);
void kvm_pmu_init(struct kvm_vcpu *vcpu);
void kvm_pmu_destroy(struct kvm_vcpu *vcpu);
bool is_vmware_backdoor_pmc(u32 pmc_idx);
extern struct kvm_pmu_ops intel_pmu_ops;
extern struct kvm_pmu_ops amd_pmu_ops;
#endif /* __KVM_X86_PMU_H */

41
arch/x86/kvm/x86.c
View File

@ -5932,23 +5932,30 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r)
static bool is_vmware_backdoor_opcode(struct x86_emulate_ctxt *ctxt)
{
if (ctxt->opcode_len != 1)
return false;
switch (ctxt->b) {
case 0xe4: /* IN */
case 0xe5:
case 0xec:
case 0xed:
case 0xe6: /* OUT */
case 0xe7:
case 0xee:
case 0xef:
case 0x6c: /* INS */
case 0x6d:
case 0x6e: /* OUTS */
case 0x6f:
return true;
switch (ctxt->opcode_len) {
case 1:
switch (ctxt->b) {
case 0xe4: /* IN */
case 0xe5:
case 0xec:
case 0xed:
case 0xe6: /* OUT */
case 0xe7:
case 0xee:
case 0xef:
case 0x6c: /* INS */
case 0x6d:
case 0x6e: /* OUTS */
case 0x6f:
return true;
}
break;
case 2:
switch (ctxt->b) {
case 0x33: /* RDPMC */
return true;
}
break;
}
return false;