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From: Jan Beulich <jbeulich@suse.com>
To: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>
Subject: [PATCH v2 4/8] x86/IRQ: avoid over-alignment in alloc_pirq_struct()
Date: Wed, 21 Apr 2021 16:57:27 +0200	[thread overview]
Message-ID: <8906088c-d76a-12ac-31d3-1375016a2148@suse.com> (raw)
In-Reply-To: <091b4b91-712f-3526-78d1-80d31faf8e41@suse.com>

In particular in the PV case xzalloc_bytes() forcing SMP_CACHE_BYTES
alignment is counterproductive, as the allocation size there is only 40
bytes. And if the code really cared about such higher than default
alignment, it should request so explicitly rather than using a type-
unsafe interface. Plus if e.g. cache line sharing was a concern, the
allocator itself should arrange to avoid such.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1313,9 +1313,12 @@ void cleanup_domain_irq_mapping(struct d
 
 struct pirq *alloc_pirq_struct(struct domain *d)
 {
-    size_t sz = is_hvm_domain(d) ? sizeof(struct pirq) :
-                                   offsetof(struct pirq, arch.hvm);
-    struct pirq *pirq = xzalloc_bytes(sz);
+    union pirq_pv {
+        char space[offsetof(struct pirq, arch.hvm)];
+        void *align;
+    };
+    struct pirq *pirq = is_hvm_domain(d) ? xzalloc(struct pirq)
+                                         : (void *)xzalloc(union pirq_pv);
 
     if ( pirq )
     {



  parent reply	other threads:[~2021-04-21 14:57 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21 14:54 [PATCH v2 0/8] assorted replacement of x[mz]alloc_bytes() Jan Beulich
2021-04-21 14:56 ` [PATCH v2 1/8] x86/MCE: avoid effectively open-coding xmalloc_array() Jan Beulich
2021-04-21 14:56 ` [PATCH v2 2/8] x86/HVM: " Jan Beulich
2021-04-21 14:57 ` [PATCH v2 3/8] x86/oprofile: " Jan Beulich
2021-04-21 14:57 ` Jan Beulich [this message]
2021-04-21 14:58 ` [PATCH v2 5/8] EFI/runtime: avoid effectively open-coding x{m,z}alloc_array() Jan Beulich
2021-04-21 14:58 ` [PATCH v2 6/8] kexec: avoid effectively open-coding xzalloc_flex_struct() Jan Beulich
2021-04-21 14:59 ` [PATCH v2 7/8] video/lfb: avoid effectively open-coding xzalloc_array() Jan Beulich
2021-04-21 14:59 ` [PATCH v2 8/8] Arm/optee: don't open-code xzalloc_flex_struct() Jan Beulich
2021-05-03 13:53   ` Ping: " Jan Beulich
2021-05-04 23:49     ` Volodymyr Babchuk
2021-04-21 15:23 ` [PATCH v2 0/8] assorted replacement of x[mz]alloc_bytes() Andrew Cooper
2021-04-21 15:32   ` Jan Beulich
2021-04-23  9:44   ` Jan Beulich

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