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Re: [PATCH] configure: define CONFIG_XEN when Xen is enabled


  • To: Peter Maydell <peter.maydell@xxxxxxxxxx>
  • From: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
  • Date: Tue, 28 Jul 2020 11:56:03 +0200
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  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Paul Durrant <pdurrant@xxxxxxxxxx>, QEMU Developers <qemu-devel@xxxxxxxxxx>, Laurent Vivier <laurent@xxxxxxxxx>, "open list:X86" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Anthony Perard <anthony.perard@xxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>
  • Delivery-date: Tue, 28 Jul 2020 09:56:11 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 7/28/20 11:53 AM, Peter Maydell wrote:
> On Tue, 28 Jul 2020 at 10:51, Philippe Mathieu-Daudé <philmd@xxxxxxxxxx> 
> wrote:
>> I'd rather uninline xen_enabled() but I'm not sure this has perf
>> penalties. Paolo is that OK to uninline it?

I suppose no because it is in various hot paths:

exec.c:588:    if (xen_enabled() && memory_access_is_direct(mr, is_write)) {
exec.c:2243:        if (xen_enabled()) {
exec.c:2326:    if (xen_enabled()) {
exec.c:2478:    } else if (xen_enabled()) {
exec.c:2525:            } else if (xen_enabled()) {
exec.c:2576:    if (xen_enabled() && block->host == NULL) {
exec.c:2609:    if (xen_enabled() && block->host == NULL) {
exec.c:2657:    if (xen_enabled()) {
exec.c:3625:        if (xen_enabled()) {
exec.c:3717:    if (xen_enabled()) {
include/exec/ram_addr.h:295:    if (!mask && !xen_enabled()) {

> 
> Can we just follow the same working pattern we already have
> for kvm_enabled() etc ?

This was the idea... I'll look at what I missed.

Phil.




 


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