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Mon, 30 Nov 2020 02:32:16 -0800 (PST) From: Oleksandr Tyshchenko To: xen-devel@lists.xenproject.org Cc: Oleksandr Tyshchenko , Stefano Stabellini , Julien Grall , Volodymyr Babchuk , Andrew Cooper , George Dunlap , Ian Jackson , Jan Beulich , Wei Liu , Paul Durrant , Julien Grall Subject: [PATCH V3 17/23] xen/ioreq: Introduce domain_has_ioreq_server() Date: Mon, 30 Nov 2020 12:31:32 +0200 Message-Id: <1606732298-22107-18-git-send-email-olekstysh@gmail.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1606732298-22107-1-git-send-email-olekstysh@gmail.com> References: <1606732298-22107-1-git-send-email-olekstysh@gmail.com> From: Oleksandr Tyshchenko 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. This involves adding an extra per-domain variable to store the count of servers in use. Signed-off-by: Oleksandr Tyshchenko CC: Julien Grall --- 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() --- --- xen/arch/arm/traps.c | 15 +++++++++------ xen/common/ioreq.c | 7 ++++++- xen/include/xen/ioreq.h | 14 ++++++++++++++ xen/include/xen/sched.h | 1 + 4 files changed, 30 insertions(+), 7 deletions(-) diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c index 4cef43e..b6077d2 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 4855dd8..f35dcf9 100644 --- a/xen/common/ioreq.c +++ b/xen/common/ioreq.c @@ -39,9 +39,14 @@ static void set_ioreq_server(struct domain *d, unsigned int id, struct ioreq_server *s) { ASSERT(id < MAX_NR_IOREQ_SERVERS); - ASSERT(!s || !d->ioreq_server.server[id]); + ASSERT(!s ^ !d->ioreq_server.server[id]); d->ioreq_server.server[id] = s; + + if ( s ) + d->ioreq_server.nr_servers++; + else + d->ioreq_server.nr_servers--; } #define GET_IOREQ_SERVER(d, id) \ diff --git a/xen/include/xen/ioreq.h b/xen/include/xen/ioreq.h index 02ff998..2289e79 100644 --- a/xen/include/xen/ioreq.h +++ b/xen/include/xen/ioreq.h @@ -55,6 +55,20 @@ struct ioreq_server { uint8_t bufioreq_handling; }; +/* + * This should only be used when d == current->domain and it's not paused, + * or when they're distinct and d is paused. Otherwise the result is + * stale before the caller can inspect it. + */ +static inline bool domain_has_ioreq_server(const struct domain *d) +{ +#ifdef CONFIG_IOREQ_SERVER + return d->ioreq_server.nr_servers; +#else + return false; +#endif +} + static inline paddr_t ioreq_mmio_first_byte(const ioreq_t *p) { return unlikely(p->df) ? diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index 8269f84..2277995 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -550,6 +550,7 @@ struct domain struct { spinlock_t lock; struct ioreq_server *server[MAX_NR_IOREQ_SERVERS]; + unsigned int nr_servers; } ioreq_server; #endif };