From: Sean Christopherson <seanjc@xxxxxxxxxx> commit 6b48fd4cb206485c357420d91ea766ef81b20dc3 upstream. Truncate RAX to 32 bits, i.e. consume EAX, when retrieving the hypecall index for a Xen hypercall. Per Xen documentation[*], the index is EAX when the vCPU is not in 64-bit mode. [*] http://xenbits.xenproject.org/docs/sphinx-unstable/guest-guide/x86/hypercall-abi.html Fixes: 23200b7a30de ("KVM: x86/xen: intercept xen hypercalls if enabled") Cc: Joao Martins <joao.m.martins@xxxxxxxxxx> Cc: David Woodhouse <dwmw@xxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Message-Id: <20210422022128.3464144-8-seanjc@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/xen.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -673,7 +673,7 @@ int kvm_xen_hypercall(struct kvm_vcpu *v bool longmode; u64 input, params[6]; - input = (u64)kvm_register_read(vcpu, VCPU_REGS_RAX); + input = (u64)kvm_register_readl(vcpu, VCPU_REGS_RAX); /* Hyper-V hypercalls get bit 31 set in EAX */ if ((input & 0x80000000) &&
