From: George Dunlap Date: Thu, 2 Aug 2018 10:12:43 +0000 (+0200) Subject: x86/altp2m: make sure EPTP_INDEX is up-to-date when enabling #VE X-Git-Tag: 4.12.0-rc1~870 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=1dddfff4c39d3db17dfa709b1c57f44e3ed352e3;p=xen.git x86/altp2m: make sure EPTP_INDEX is up-to-date when enabling #VE vmx_vmexit_handler() assumes that if SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS is set, that the value in EPTP_INDEX is valid. Unfortunately, the function which sets this bit (vmx_vcpu_update_vmfunc_ve) doesn't actually set EPTP_INDEX; it will only be set the next time vmx_vcpu_update_eptp() is called. This means that if a vcpu makes a vmexit between these two points, the EPTP_INDEX it reads will be invalid. The first time this race happens for a domain, EPTP_INDEX will most likely be zero, which is the index for the "host" p2m -- and thus is often correct. But the second time this race happens, the value will typically be INVALID_ALTP2M, which will hit the following BUG: BUG_ON(idx >= MAX_ALTP2M); Worse, if for some reason the current altp2m was *not* `0` during this window (say, because a toolstack changed the VM to a different view), then the accounting of active vcpus for an altp2m will be thrown off. Fix this by always updating EPTP_INDEX to the current altp2m index when enabling #VE. Reported-by: Razvan Cojocaru Signed-off-by: George Dunlap Reviewed-by: Razvan Cojocaru Tested-by: Razvan Cojocaru Acked-by: Kevin Tian --- diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c index 257efbe322..420e875fcf 100644 --- a/xen/arch/x86/hvm/vmx/vmx.c +++ b/xen/arch/x86/hvm/vmx/vmx.c @@ -2191,7 +2191,14 @@ static void vmx_vcpu_update_vmfunc_ve(struct vcpu *v) mfn = get_gfn_query_unlocked(d, gfn_x(vcpu_altp2m(v).veinfo_gfn), &t); if ( !mfn_eq(mfn, INVALID_MFN) ) + { __vmwrite(VIRT_EXCEPTION_INFO, mfn_x(mfn) << PAGE_SHIFT); + /* + * Make sure we have an up-to-date EPTP_INDEX when + * setting SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS. + */ + __vmwrite(EPTP_INDEX, vcpu_altp2m(v).p2midx); + } else v->arch.hvm_vmx.secondary_exec_control &= ~SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS;