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KVM: x86/xen: re-initialize shared_info if guest (32/64-bit) mode is set

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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: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20240215152916.1158-12-paul@xen.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Paul Durrant 2024-02-15 15:29:06 +00:00 • committed by Sean Christopherson
parent c01c55a34f
commit 18b99e4d6d
1 changed files with 26 additions and 3 deletions
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29
arch/x86/kvm/xen.c
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@ -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