Commit 18b99e4d authored by Paul Durrant's avatar Paul Durrant Committed by Sean Christopherson
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KVM: x86/xen: re-initialize shared_info if guest (32/64-bit) mode is set 



If the shared_info PFN cache has already been initialized then the content
of the shared_info page needs to be re-initialized whenever the guest
mode is (re)set.
Setting the guest mode is either done explicitly by the VMM via the
KVM_XEN_ATTR_TYPE_LONG_MODE attribute, or implicitly when the guest writes
the MSR to set up the hypercall page.

Signed-off-by: default avatarPaul Durrant <pdurrant@amazon.com>
Reviewed-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20240215152916.1158-12-paul@xen.org


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent c01c55a3

arch/x86/kvm/xen.c

+26 −3
Original line number Diff line number Diff line
@@ -625,8 +625,16 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) 
		} else {

			mutex_lock(&kvm->arch.xen.xen_lock);

			kvm->arch.xen.long_mode = !!data->u.long_mode;



			/*

			 * Re-initialize shared_info to put the wallclock in the

			 * correct place. Whilst it's not necessary to do this

			 * unless the mode is actually changed, it does no harm

			 * to make the call anyway.

			 */

			r = kvm->arch.xen.shinfo_cache.active ?

				kvm_xen_shared_info_init(kvm) : 0;

			mutex_unlock(&kvm->arch.xen.xen_lock);

			r = 0;

		}

		break;
@@ -1101,9 +1109,24 @@ int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data) 
	u32 page_num = data & ~PAGE_MASK;

	u64 page_addr = data & PAGE_MASK;

	bool lm = is_long_mode(vcpu);

	int r = 0;



	/* Latch long_mode for shared_info pages etc. */

	vcpu->kvm->arch.xen.long_mode = lm;

	mutex_lock(&kvm->arch.xen.xen_lock);

	if (kvm->arch.xen.long_mode != lm) {

		kvm->arch.xen.long_mode = lm;



		/*

		 * Re-initialize shared_info to put the wallclock in the

		 * correct place.

		 */

		if (kvm->arch.xen.shinfo_cache.active &&

		    kvm_xen_shared_info_init(kvm))

			r = 1;

	}

	mutex_unlock(&kvm->arch.xen.xen_lock);



	if (r)

		return r;



	/*

	 * If Xen hypercall intercept is enabled, fill the hypercall