xen/arch/x86/include/asm/domain.h | 8 +++++++- xen/arch/x86/traps.c | 6 ++++++ xen/include/public/arch-x86/cpuid.h | 5 +++++ 3 files changed, 18 insertions(+), 1 deletion(-)
Have is_hvm_pv_evtchn_domain() return true for vector callbacks for
evtchn delivery set up on a per-vCPU basis via
HVMOP_set_evtchn_upcall_vector.
is_hvm_pv_evtchn_domain() returning true is a condition for setting up
physical IRQ to event channel mappings.
Therefore, a CPUID bit is added so that guests know whether the check
in is_hvm_pv_evtchn_domain() will fail when using
HVMOP_set_evtchn_upcall_vector. This matters for guests that route
PIRQs over event channels since is_hvm_pv_evtchn_domain() is a
condition in physdev_map_pirq().
The naming of the CPUID bit is quite generic about upcall support
being available. That's done so that the define name doesn't become
overly long like XEN_HVM_CPUID_UPCALL_VECTOR_SUPPORTS_PIRQ or some
such.
A guest that doesn't care about physical interrupts routed over event
channels can just test for the availability of the hypercall directly
(HVMOP_set_evtchn_upcall_vector) without checking the CPUID bit.
Signed-off-by: Jane Malalane <jane.malalane@citrix.com>
---
CC: Jan Beulich <jbeulich@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: "Roger Pau Monné" <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
v3:
* Improve commit message and title.
v2:
* Since the naming of the CPUID bit is quite generic, better explain
when it should be checked for, in code comments and commit message.
---
xen/arch/x86/include/asm/domain.h | 8 +++++++-
xen/arch/x86/traps.c | 6 ++++++
xen/include/public/arch-x86/cpuid.h | 5 +++++
3 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/include/asm/domain.h b/xen/arch/x86/include/asm/domain.h
index 35898d725f..f044e0a492 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -14,8 +14,14 @@
#define has_32bit_shinfo(d) ((d)->arch.has_32bit_shinfo)
+/*
+ * Set to true if either the global vector-type callback or per-vCPU
+ * LAPIC vectors are used. Assume all vCPUs will use
+ * HVMOP_set_evtchn_upcall_vector as long as the initial vCPU does.
+ */
#define is_hvm_pv_evtchn_domain(d) (is_hvm_domain(d) && \
- (d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector)
+ ((d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector || \
+ (d)->vcpu[0]->arch.hvm.evtchn_upcall_vector))
#define is_hvm_pv_evtchn_vcpu(v) (is_hvm_pv_evtchn_domain(v->domain))
#define is_domain_direct_mapped(d) ((void)(d), 0)
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 25bffe47d7..1a7f9df067 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1152,6 +1152,12 @@ void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t leaf,
res->a |= XEN_HVM_CPUID_DOMID_PRESENT;
res->c = d->domain_id;
+ /*
+ * Per-vCPU event channel upcalls are implemented and work
+ * correctly with PIRQs routed over event channels.
+ */
+ res->a |= XEN_HVM_CPUID_UPCALL_VECTOR;
+
break;
case 5: /* PV-specific parameters */
diff --git a/xen/include/public/arch-x86/cpuid.h b/xen/include/public/arch-x86/cpuid.h
index f2b2b3632c..c49eefeaf8 100644
--- a/xen/include/public/arch-x86/cpuid.h
+++ b/xen/include/public/arch-x86/cpuid.h
@@ -109,6 +109,11 @@
* field from 8 to 15 bits, allowing to target APIC IDs up 32768.
*/
#define XEN_HVM_CPUID_EXT_DEST_ID (1u << 5)
+/*
+ * Per-vCPU event channel upcalls work correctly with physical IRQs
+ * bound to event channels.
+ */
+#define XEN_HVM_CPUID_UPCALL_VECTOR (1u << 6)
/*
* Leaf 6 (0x40000x05)
--
2.11.0
On 18.05.2022 15:27, Jane Malalane wrote: > --- a/xen/arch/x86/include/asm/domain.h > +++ b/xen/arch/x86/include/asm/domain.h > @@ -14,8 +14,14 @@ > > #define has_32bit_shinfo(d) ((d)->arch.has_32bit_shinfo) > > +/* > + * Set to true if either the global vector-type callback or per-vCPU > + * LAPIC vectors are used. Assume all vCPUs will use > + * HVMOP_set_evtchn_upcall_vector as long as the initial vCPU does. > + */ > #define is_hvm_pv_evtchn_domain(d) (is_hvm_domain(d) && \ > - (d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector) > + ((d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector || \ > + (d)->vcpu[0]->arch.hvm.evtchn_upcall_vector)) > #define is_hvm_pv_evtchn_vcpu(v) (is_hvm_pv_evtchn_domain(v->domain)) I continue to think that with the vCPU0 dependency added to is_hvm_pv_evtchn_domain(), is_hvm_pv_evtchn_vcpu() should either be adjusted as well (to check the correct vCPU's field) or be deleted (and the sole caller be replaced). Jan
On 24/05/2022 16:14, Jan Beulich wrote: > [CAUTION - EXTERNAL EMAIL] DO NOT reply, click links, or open attachments unless you have verified the sender and know the content is safe. > > On 18.05.2022 15:27, Jane Malalane wrote: >> --- a/xen/arch/x86/include/asm/domain.h >> +++ b/xen/arch/x86/include/asm/domain.h >> @@ -14,8 +14,14 @@ >> >> #define has_32bit_shinfo(d) ((d)->arch.has_32bit_shinfo) >> >> +/* >> + * Set to true if either the global vector-type callback or per-vCPU >> + * LAPIC vectors are used. Assume all vCPUs will use >> + * HVMOP_set_evtchn_upcall_vector as long as the initial vCPU does. >> + */ >> #define is_hvm_pv_evtchn_domain(d) (is_hvm_domain(d) && \ >> - (d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector) >> + ((d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector || \ >> + (d)->vcpu[0]->arch.hvm.evtchn_upcall_vector)) >> #define is_hvm_pv_evtchn_vcpu(v) (is_hvm_pv_evtchn_domain(v->domain)) > > I continue to think that with the vCPU0 dependency added to > is_hvm_pv_evtchn_domain(), is_hvm_pv_evtchn_vcpu() should either > be adjusted as well (to check the correct vCPU's field) or be > deleted (and the sole caller be replaced). > > Jan I will replace it in a newer version of the patch. Thank you. Jane.
On Tue, May 24, 2022 at 05:14:12PM +0200, Jan Beulich wrote: > On 18.05.2022 15:27, Jane Malalane wrote: > > --- a/xen/arch/x86/include/asm/domain.h > > +++ b/xen/arch/x86/include/asm/domain.h > > @@ -14,8 +14,14 @@ > > > > #define has_32bit_shinfo(d) ((d)->arch.has_32bit_shinfo) > > > > +/* > > + * Set to true if either the global vector-type callback or per-vCPU > > + * LAPIC vectors are used. Assume all vCPUs will use > > + * HVMOP_set_evtchn_upcall_vector as long as the initial vCPU does. > > + */ > > #define is_hvm_pv_evtchn_domain(d) (is_hvm_domain(d) && \ > > - (d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector) > > + ((d)->arch.hvm.irq->callback_via_type == HVMIRQ_callback_vector || \ > > + (d)->vcpu[0]->arch.hvm.evtchn_upcall_vector)) > > #define is_hvm_pv_evtchn_vcpu(v) (is_hvm_pv_evtchn_domain(v->domain)) > > I continue to think that with the vCPU0 dependency added to > is_hvm_pv_evtchn_domain(), is_hvm_pv_evtchn_vcpu() should either > be adjusted as well (to check the correct vCPU's field) or be > deleted (and the sole caller be replaced). I would be fine with replacing, the sole caller of is_hvm_pv_evtchn_vcpu(v) is never reached if the upcall vector is in use. Thanks, Roger.
Subject could a little shorter I think: x86/hvm: fix upcall vector usage with PIRQs on event channels On Wed, May 18, 2022 at 02:27:14PM +0100, Jane Malalane wrote: > Have is_hvm_pv_evtchn_domain() return true for vector callbacks for > evtchn delivery set up on a per-vCPU basis via > HVMOP_set_evtchn_upcall_vector. > > is_hvm_pv_evtchn_domain() returning true is a condition for setting up > physical IRQ to event channel mappings. > > Therefore, a CPUID bit is added so that guests know whether the check > in is_hvm_pv_evtchn_domain() will fail when using > HVMOP_set_evtchn_upcall_vector. This matters for guests that route > PIRQs over event channels since is_hvm_pv_evtchn_domain() is a > condition in physdev_map_pirq(). > > The naming of the CPUID bit is quite generic about upcall support > being available. That's done so that the define name doesn't become > overly long like XEN_HVM_CPUID_UPCALL_VECTOR_SUPPORTS_PIRQ or some > such. I think you can drop the "... like XEN_HVM_CPUID_UPCALL_VECTOR_SUPPORTS_PIRQ or some such." That's maybe too informal for a commit message log. > > A guest that doesn't care about physical interrupts routed over event > channels can just test for the availability of the hypercall directly > (HVMOP_set_evtchn_upcall_vector) without checking the CPUID bit. > > Signed-off-by: Jane Malalane <jane.malalane@citrix.com> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> (I think the above can be fixed on commit if the committer agrees) One thing that worries me is how to differentiate between callbacks setup with HVM_PARAM_CALLBACK_TYPE_VECTOR vs using HVMOP_set_evtchn_upcall_vector in writing. We usually use 'callback vector' to refer to the former and 'upcall vector' to refer to the later. Hope that's clearer enough. Thanks, Roger.
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