Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 22/04/21 11:51, Vitaly Kuznetsov wrote: >> Sean Christopherson <seanjc@xxxxxxxxxx> writes: >> >>> 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> >>> --- >>> arch/x86/kvm/xen.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c >>> index ae17250e1efe..7f27bb65a572 100644 >>> --- a/arch/x86/kvm/xen.c >>> +++ b/arch/x86/kvm/xen.c >>> @@ -673,7 +673,7 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu) >>> 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) && >> >> Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> >> >> Alternatively, as a minor optimization, you could've used '!longmode' >> check below, something like: >> >> diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c >> index ae17250e1efe..7df1498d3a41 100644 >> --- a/arch/x86/kvm/xen.c >> +++ b/arch/x86/kvm/xen.c >> @@ -682,6 +682,7 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu) >> >> longmode = is_64_bit_mode(vcpu); >> if (!longmode) { >> + input = (u32)input; >> params[0] = (u32)kvm_rbx_read(vcpu); >> params[1] = (u32)kvm_rcx_read(vcpu); >> params[2] = (u32)kvm_rdx_read(vcpu); >> > > You haven't seen patch 9 yet. :) > True; suggestion dismissed :-) -- Vitaly
