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Commit 8322ebbb authored by David Matlack's avatar David Matlack Committed by Paolo Bonzini
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KVM: nVMX: generate MSR_IA32_CR{0,4}_FIXED1 from guest CPUID 



MSR_IA32_CR{0,4}_FIXED1 define which bits in CR0 and CR4 are allowed to
be 1 during VMX operation. Since the set of allowed-1 bits is the same
in and out of VMX operation, we can generate these MSRs entirely from
the guest's CPUID. This lets userspace avoiding having to save/restore
these MSRs.

This patch also initializes MSR_IA32_CR{0,4}_FIXED1 from the CPU's MSRs
by default. This is a saner than the current default of -1ull, which
includes bits that the host CPU does not support.

Signed-off-by: default avatarDavid Matlack <dmatlack@google.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent 3899152c

arch/x86/kvm/vmx.c

+52 −3
Original line number Diff line number Diff line
@@ -2877,16 +2877,18 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx) 
		vmx->nested.nested_vmx_basic |= VMX_BASIC_INOUT;



	/*

	 * These MSRs specify bits which the guest must keep fixed (on or off)

	 * These MSRs specify bits which the guest must keep fixed on

	 * while L1 is in VMXON mode (in L1's root mode, or running an L2).

	 * We picked the standard core2 setting.

	 */

#define VMXON_CR0_ALWAYSON     (X86_CR0_PE | X86_CR0_PG | X86_CR0_NE)

#define VMXON_CR4_ALWAYSON     X86_CR4_VMXE

	vmx->nested.nested_vmx_cr0_fixed0 = VMXON_CR0_ALWAYSON;

	vmx->nested.nested_vmx_cr0_fixed1 = -1ULL;

	vmx->nested.nested_vmx_cr4_fixed0 = VMXON_CR4_ALWAYSON;

	vmx->nested.nested_vmx_cr4_fixed1 = -1ULL;



	/* These MSRs specify bits which the guest must keep fixed off. */

	rdmsrl(MSR_IA32_VMX_CR0_FIXED1, vmx->nested.nested_vmx_cr0_fixed1);

	rdmsrl(MSR_IA32_VMX_CR4_FIXED1, vmx->nested.nested_vmx_cr4_fixed1);



	/* highest index: VMX_PREEMPTION_TIMER_VALUE */

	vmx->nested.nested_vmx_vmcs_enum = 0x2e;
@@ -9424,6 +9426,50 @@ static void vmcs_set_secondary_exec_control(u32 new_ctl) 
		     (new_ctl & ~mask) | (cur_ctl & mask));

}



/*

 * Generate MSR_IA32_VMX_CR{0,4}_FIXED1 according to CPUID. Only set bits

 * (indicating "allowed-1") if they are supported in the guest's CPUID.

 */

static void nested_vmx_cr_fixed1_bits_update(struct kvm_vcpu *vcpu)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	struct kvm_cpuid_entry2 *entry;



	vmx->nested.nested_vmx_cr0_fixed1 = 0xffffffff;

	vmx->nested.nested_vmx_cr4_fixed1 = X86_CR4_PCE;



#define cr4_fixed1_update(_cr4_mask, _reg, _cpuid_mask) do {		\

	if (entry && (entry->_reg & (_cpuid_mask)))			\

		vmx->nested.nested_vmx_cr4_fixed1 |= (_cr4_mask);	\

} while (0)



	entry = kvm_find_cpuid_entry(vcpu, 0x1, 0);

	cr4_fixed1_update(X86_CR4_VME,        edx, bit(X86_FEATURE_VME));

	cr4_fixed1_update(X86_CR4_PVI,        edx, bit(X86_FEATURE_VME));

	cr4_fixed1_update(X86_CR4_TSD,        edx, bit(X86_FEATURE_TSC));

	cr4_fixed1_update(X86_CR4_DE,         edx, bit(X86_FEATURE_DE));

	cr4_fixed1_update(X86_CR4_PSE,        edx, bit(X86_FEATURE_PSE));

	cr4_fixed1_update(X86_CR4_PAE,        edx, bit(X86_FEATURE_PAE));

	cr4_fixed1_update(X86_CR4_MCE,        edx, bit(X86_FEATURE_MCE));

	cr4_fixed1_update(X86_CR4_PGE,        edx, bit(X86_FEATURE_PGE));

	cr4_fixed1_update(X86_CR4_OSFXSR,     edx, bit(X86_FEATURE_FXSR));

	cr4_fixed1_update(X86_CR4_OSXMMEXCPT, edx, bit(X86_FEATURE_XMM));

	cr4_fixed1_update(X86_CR4_VMXE,       ecx, bit(X86_FEATURE_VMX));

	cr4_fixed1_update(X86_CR4_SMXE,       ecx, bit(X86_FEATURE_SMX));

	cr4_fixed1_update(X86_CR4_PCIDE,      ecx, bit(X86_FEATURE_PCID));

	cr4_fixed1_update(X86_CR4_OSXSAVE,    ecx, bit(X86_FEATURE_XSAVE));



	entry = kvm_find_cpuid_entry(vcpu, 0x7, 0);

	cr4_fixed1_update(X86_CR4_FSGSBASE,   ebx, bit(X86_FEATURE_FSGSBASE));

	cr4_fixed1_update(X86_CR4_SMEP,       ebx, bit(X86_FEATURE_SMEP));

	cr4_fixed1_update(X86_CR4_SMAP,       ebx, bit(X86_FEATURE_SMAP));

	cr4_fixed1_update(X86_CR4_PKE,        ecx, bit(X86_FEATURE_PKU));

	/* TODO: Use X86_CR4_UMIP and X86_FEATURE_UMIP macros */

	cr4_fixed1_update(bit(11),            ecx, bit(2));



#undef cr4_fixed1_update

}



static void vmx_cpuid_update(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *best;
@@ -9465,6 +9511,9 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu) 
	else

		to_vmx(vcpu)->msr_ia32_feature_control_valid_bits &=

			~FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;



	if (nested_vmx_allowed(vcpu))

		nested_vmx_cr_fixed1_bits_update(vcpu);

}



static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)