Mailing List Archive

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

This patch introduces a helper the main purpose of which is to check
if a domain is using IOREQ server(s).

On Arm the current benefit is to avoid calling vcpu_ioreq_handle_completion()
(which implies iterating over all possible IOREQ servers anyway)
on every return in leave_hypervisor_to_guest() if there is no active
servers for the particular domain.
Also this helper will be used by one of the subsequent patches on Arm.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
CC: Julien Grall <julien.grall@arm.com>
[On Arm only]
Tested-by: Wei Chen <Wei.Chen@arm.com>

---
Please note, this is a split/cleanup/hardening of Julien's PoC:
"Add support for Guest IO forwarding to a device emulator"

Changes RFC -> V1:
- new patch

Changes V1 -> V2:
- update patch description
- guard helper with CONFIG_IOREQ_SERVER
- remove "hvm" prefix
- modify helper to just return d->arch.hvm.ioreq_server.nr_servers
- put suitable ASSERT()s
- use ASSERT(d->ioreq_server.server[id] ? !s : !!s) in set_ioreq_server()
- remove d->ioreq_server.nr_servers = 0 from hvm_ioreq_init()

Changes V2 -> V3:
- update patch description
- remove ASSERT()s from the helper, add a comment
- use #ifdef CONFIG_IOREQ_SERVER inside function body
- use new ASSERT() construction in set_ioreq_server()

Changes V3 -> V4:
- update patch description
- drop per-domain variable "nr_servers"
- reimplement a helper to count the non-NULL entries
- make the helper out-of-line
---
xen/arch/arm/traps.c | 15 +++++++++------
xen/common/ioreq.c | 16 ++++++++++++++++
xen/include/xen/ioreq.h | 2 ++
3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 4a83e1e..35094d8 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2262,14 +2262,17 @@ static bool check_for_vcpu_work(void)
struct vcpu *v = current;

#ifdef CONFIG_IOREQ_SERVER
- bool handled;
+ if ( domain_has_ioreq_server(v->domain) )
+ {
+ bool handled;

- local_irq_enable();
- handled = vcpu_ioreq_handle_completion(v);
- local_irq_disable();
+ local_irq_enable();
+ handled = vcpu_ioreq_handle_completion(v);
+ local_irq_disable();

- if ( !handled )
- return true;
+ if ( !handled )
+ return true;
+ }
#endif

if ( likely(!v->arch.need_flush_to_ram) )
diff --git a/xen/common/ioreq.c b/xen/common/ioreq.c
index d5f4dd3..59f4990 100644
--- a/xen/common/ioreq.c
+++ b/xen/common/ioreq.c
@@ -80,6 +80,22 @@ static ioreq_t *get_ioreq(struct ioreq_server *s, struct vcpu *v)
return &p->vcpu_ioreq[v->vcpu_id];
}

+/*
+ * This should only be used when d == current->domain or when they're
+ * distinct and d is paused. Otherwise the result is stale before
+ * the caller can inspect it.
+ */
+bool domain_has_ioreq_server(const struct domain *d)
+{
+ const struct ioreq_server *s;
+ unsigned int id;
+
+ FOR_EACH_IOREQ_SERVER(d, id, s)
+ return true;
+
+ return false;
+}
+
static struct ioreq_vcpu *get_pending_vcpu(const struct vcpu *v,
struct ioreq_server **srvp)
{
diff --git a/xen/include/xen/ioreq.h b/xen/include/xen/ioreq.h
index ec7e98d..f0908af 100644
--- a/xen/include/xen/ioreq.h
+++ b/xen/include/xen/ioreq.h
@@ -81,6 +81,8 @@ static inline bool ioreq_needs_completion(const ioreq_t *ioreq)
#define HANDLE_BUFIOREQ(s) \
((s)->bufioreq_handling != HVM_IOREQSRV_BUFIOREQ_OFF)

+bool domain_has_ioreq_server(const struct domain *d);
+
bool vcpu_ioreq_pending(struct vcpu *v);
bool vcpu_ioreq_handle_completion(struct vcpu *v);
bool is_ioreq_server_page(struct domain *d, const struct page_info *page);
--
2.7.4