Commit a4dae7c7 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86: Allow vendor code to disable quirks 



In some cases, the handling of quirks is split between platform-specific
code and generic code, or it is done entirely in generic code, but the
relevant bug does not trigger on some platforms; for example,
this will be the case for "ignore guest PAT".  Allow unaffected vendor
modules to disable handling of a quirk for all VMs via a new entry in
kvm_caps.

Such quirks remain available in KVM_CAP_DISABLE_QUIRKS2, because that API
tells userspace that KVM *knows* that some of its past behavior was bogus
or just undesirable.  In other words, it's plausible for userspace to
refuse to run if a quirk is not listed by KVM_CAP_DISABLE_QUIRKS2, so
preserve that and make it part of the API.

As an example, mark KVM_X86_QUIRK_CD_NW_CLEARED as auto-disabled on
Intel systems.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 9966b782

arch/x86/include/asm/kvm_host.h

+3 −0
Original line number Diff line number Diff line
@@ -2422,6 +2422,9 @@ int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages); 
	 KVM_X86_QUIRK_SLOT_ZAP_ALL |		\

	 KVM_X86_QUIRK_STUFF_FEATURE_MSRS)



#define KVM_X86_CONDITIONAL_QUIRKS		\

	 KVM_X86_QUIRK_CD_NW_CLEARED



/*

 * KVM previously used a u32 field in kvm_run to indicate the hypercall was

 * initiated from long mode. KVM now sets bit 0 to indicate long mode, but the

arch/x86/kvm/svm/svm.c

+1 −0
Original line number Diff line number Diff line
@@ -5472,6 +5472,7 @@ static __init int svm_hardware_setup(void) 
	 */

	allow_smaller_maxphyaddr = !npt_enabled;



	kvm_caps.inapplicable_quirks &= ~KVM_X86_QUIRK_CD_NW_CLEARED;

	return 0;



err:

arch/x86/kvm/x86.c

+2 −0
Original line number Diff line number Diff line
@@ -9783,6 +9783,7 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) 
		kvm_host.xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);

		kvm_caps.supported_xcr0 = kvm_host.xcr0 & KVM_SUPPORTED_XCR0;

	}

	kvm_caps.inapplicable_quirks = KVM_X86_CONDITIONAL_QUIRKS;



	rdmsrl_safe(MSR_EFER, &kvm_host.efer);
@@ -12733,6 +12734,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 
	/* Decided by the vendor code for other VM types.  */

	kvm->arch.pre_fault_allowed =

		type == KVM_X86_DEFAULT_VM || type == KVM_X86_SW_PROTECTED_VM;

	kvm->arch.disabled_quirks = kvm_caps.inapplicable_quirks;



	ret = kvm_page_track_init(kvm);

	if (ret)

arch/x86/kvm/x86.h

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ struct kvm_caps { 
	u64 supported_xcr0;

	u64 supported_xss;

	u64 supported_perf_cap;

	u64 inapplicable_quirks;

};



struct kvm_host_values {