Commit 2d7921c4 authored by Arbel Moshe's avatar Arbel Moshe Committed by Paolo Bonzini
Browse files

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

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: default avatarArbel Moshe <arbel.moshe@oracle.com>
Signed-off-by: default avatarLiran Alon <liran.alon@oracle.com>
Reviewed-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 9718420e

arch/x86/kvm/emulate.c

+8 −0
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/pmu.c

+37 −0
Original line number Diff line number Diff line
@@ -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;

arch/x86/kvm/pmu.h

+6 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kvm/x86.c

+24 −17
Original line number Diff line number Diff line
@@ -5932,9 +5932,8 @@ 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->opcode_len) {

	case 1:

		switch (ctxt->b) {

		case 0xe4:	/* IN */

		case 0xe5:
@@ -5950,6 +5949,14 @@ static bool is_vmware_backdoor_opcode(struct x86_emulate_ctxt *ctxt) 
		case 0x6f:

			return true;

		}

		break;

	case 2:

		switch (ctxt->b) {

		case 0x33:	/* RDPMC */

			return true;

		}

		break;

	}



	return false;

}

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