Hi Oleksandr,
On 03/09/2021 09:33, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>
vPCI may map and unmap PCI device memory (BARs) being passed through which
may take a lot of time. For this those operations may be deferred to be
performed later, so that they can be safely preempted.
Run the corresponding vPCI code while switching a vCPU.
IIUC, you are talking about the function map_range() in
xen/drivers/vpci/header. The function has the following todo for Arm:
/*
* ARM TODOs:
* - On ARM whether the memory is prefetchable or not should be
passed
* to map_mmio_regions in order to decide which memory attributes
* should be used.
*
* - {un}map_mmio_regions doesn't support preemption.
*/
This doesn't seem to be addressed in the two series for PCI passthrough
sent so far. Do you have any plan to handle it?
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>
---
xen/arch/arm/traps.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 219ab3c3fbde..1571fb8afd03 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -34,6 +34,7 @@
#include <xen/symbols.h>
#include <xen/version.h>
#include <xen/virtual_region.h>
+#include <xen/vpci.h>
#include <public/sched.h>
#include <public/xen.h>
@@ -2304,6 +2305,11 @@ static bool check_for_vcpu_work(void)
}
#endif
+ local_irq_enable();
+ if ( has_vpci(v->domain) && vpci_process_pending(v) )
Looking at the code of vpci_process_pending(), it looks like there are
some rework to do for guest. Do you plan to handle it as part of the
vPCI series?
+ raise_softirq(SCHEDULE_SOFTIRQ);
+ local_irq_disable();
+
From my understanding of vcpi_process_pending(). The function will
return true if there are more work to schedule. However, if
check_for_vcpu_for_work() return false, then we will return to the guest
before any work for vCPI has finished. This is because
check_for_vcpu_work() will not be called again.
In this case, I think you want to return as soon as you know we need to
reschedule.
However, looking at the rest of the code, we already have a check for
vpci in the common IOREQ code. So we would end up to call twice
vpci_process_pending(). Maybe we should move the call from the IOREQ to
arch-code.
Cheers,
--
Julien Grall
