From: "Jan Beulich" <JBeulich@suse.com>
To: xen-devel <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Wei Liu <wei.liu2@citrix.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: [PATCH v7 01/10] x86: reduce general stack alignment to 8
Date: Tue, 12 Mar 2019 08:03:50 -0600 [thread overview]
Message-ID: <5C87BC46020000780021DC70@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <5C87BB28020000780021DC59@prv1-mh.provo.novell.com>
We don't need bigger alignment except when calling EFI boot or runtime
services functions (and we don't guarantee that either, as explained
close to the top of xen/common/efi/runtime.c in the struct efi_rs_state
declaration). Hence if the compiler supports reducing stack alignment
from the ABI compatible 16 bytes (gcc 7 and newer), do so wherever
possible.
The EFI case itself is largely dealt with already (actually forcing
32-byte alignment) as a result of commit f6b7fedc89 ("x86/EFI: meet
further spec requirements for runtime calls"). However, as explained in
the description of that earlier change, without using
-mincoming-stack-boundary=3 (which we don't want) we still have to make
the compiler assume 16-byte stack boundaries for CUs making EFI calls in
order to keep the compiler from aligning the stack, but then placing an
odd number of 8-byte objects on it, resulting in a mis-aligned outgoing
stack.
This as a side effect yields some code size reduction, since for a
number of sufficiently simple non-leaf functions the stack adjustment
(by 8, when there are no local stack variables at all) gets dropped
altogether. I notice exceptions though, for example in guest_cpuid(),
where in a release build gcc 8.2 now decides to set up a frame pointer
(without ever using %rbp); I consider this a compiler quirk which we
should leave to the compiler folks to address eventually.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
---
v5: New.
--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -52,6 +52,11 @@ CFLAGS += -fno-jump-tables
export CONFIG_INDIRECT_THUNK=y
endif
+# If supported by the compiler, reduce stack alignment to 8 bytes. But allow
+# this to be overridden elsewhere.
+$(call cc-option-add,CFLAGS-stack-boundary,CC,-mpreferred-stack-boundary=3)
+CFLAGS += $(CFLAGS-stack-boundary)
+
# Set up the assembler include path properly for older toolchains.
CFLAGS += -Wa,-I$(BASEDIR)/include
--- a/xen/arch/x86/efi/Makefile
+++ b/xen/arch/x86/efi/Makefile
@@ -5,7 +5,11 @@ CFLAGS += -fshort-wchar
boot.init.o: buildid.o
+EFIOBJ := boot.init.o compat.o runtime.o
+
+$(EFIOBJ): CFLAGS-stack-boundary := -mpreferred-stack-boundary=4
+
obj-y := stub.o
-obj-$(XEN_BUILD_EFI) := boot.init.o compat.o relocs-dummy.o runtime.o
+obj-$(XEN_BUILD_EFI) := $(EFIOBJ) relocs-dummy.o
extra-$(XEN_BUILD_EFI) += buildid.o
nocov-$(XEN_BUILD_EFI) += stub.o
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next prev parent reply other threads:[~2019-03-12 14:03 UTC|newest]
Thread overview: 119+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-11 13:26 [PATCH v3 0/9] x86: indirect call overhead reduction Jan Beulich
2018-09-11 13:32 ` [PATCH v3 1/9] x86: infrastructure to allow converting certain indirect calls to direct ones Jan Beulich
2018-09-21 10:49 ` Wei Liu
2018-09-21 11:47 ` Jan Beulich
2018-09-21 13:48 ` Wei Liu
2018-09-21 15:26 ` Jan Beulich
2018-09-26 11:06 ` Wei Liu
2018-09-11 13:32 ` [PATCH v3 2/9] x86/HVM: patch indirect calls through hvm_funcs " Jan Beulich
2018-09-21 10:50 ` Wei Liu
2018-09-11 13:33 ` [PATCH v3 3/9] x86/HVM: patch vINTR " Jan Beulich
2018-09-21 10:50 ` Wei Liu
2018-09-11 13:34 ` [PATCH v3 4/9] x86: patch ctxt_switch_masking() indirect call to direct one Jan Beulich
2018-09-21 10:51 ` Wei Liu
2018-09-11 13:35 ` [PATCH v3 5/9] x86/genapic: remove indirection from genapic hook accesses Jan Beulich
2018-09-21 10:53 ` Wei Liu
2018-09-11 13:35 ` [PATCH v3 6/9] x86/genapic: patch indirect calls to direct ones Jan Beulich
2018-09-21 11:03 ` Wei Liu
2018-09-21 11:53 ` Jan Beulich
2018-09-21 13:55 ` Wei Liu
2018-09-11 13:35 ` [PATCH v3 7/9] x86/cpuidle: patch some " Jan Beulich
2018-09-21 14:01 ` Wei Liu
2018-09-11 13:37 ` [PATCH v3 8/9] cpufreq: convert to a single post-init driver (hooks) instance Jan Beulich
2018-09-21 14:06 ` Wei Liu
2018-09-11 13:37 ` [PATCH v3 9/9] cpufreq: patch target() indirect call to direct one Jan Beulich
2018-09-21 14:06 ` Wei Liu
2018-10-02 10:09 ` [PATCH v4 00/12] x86: indirect call overhead reduction Jan Beulich
2018-10-02 10:12 ` [PATCH v4 01/12] x86: infrastructure to allow converting certain indirect calls to direct ones Jan Beulich
2018-10-02 13:21 ` Andrew Cooper
2018-10-02 13:28 ` Julien Grall
2018-10-02 13:35 ` Andrew Cooper
2018-10-02 13:36 ` Julien Grall
2018-10-02 14:06 ` Jan Beulich
2018-10-02 14:23 ` Andrew Cooper
2018-10-02 14:43 ` Jan Beulich
2018-10-02 15:40 ` Andrew Cooper
2018-10-02 16:06 ` Jan Beulich
2018-10-02 13:55 ` Wei Liu
2018-10-02 14:08 ` Jan Beulich
2018-10-03 18:38 ` Andrew Cooper
2018-10-05 12:39 ` Andrew Cooper
2018-10-05 13:43 ` Jan Beulich
2018-10-05 14:49 ` Andrew Cooper
2018-10-05 15:05 ` Jan Beulich
2018-10-29 11:01 ` Jan Beulich
2018-10-02 10:12 ` [PATCH v4 02/12] x86/HVM: patch indirect calls through hvm_funcs " Jan Beulich
2018-10-02 13:18 ` Paul Durrant
2018-10-03 18:55 ` Andrew Cooper
2018-10-04 10:19 ` Jan Beulich
2018-10-02 10:13 ` [PATCH v4 03/12] x86/HVM: patch vINTR " Jan Beulich
2018-10-03 19:01 ` Andrew Cooper
2018-10-02 10:13 ` [PATCH v4 04/12] x86: patch ctxt_switch_masking() indirect call to direct one Jan Beulich
2018-10-03 19:01 ` Andrew Cooper
2018-10-02 10:14 ` [PATCH v4 05/12] x86/genapic: remove indirection from genapic hook accesses Jan Beulich
2018-10-03 19:04 ` Andrew Cooper
2018-10-02 10:14 ` [PATCH v4 06/12] x86/genapic: patch indirect calls to direct ones Jan Beulich
2018-10-03 19:07 ` Andrew Cooper
2018-10-02 10:15 ` [PATCH v4 07/12] x86/cpuidle: patch some " Jan Beulich
2018-10-04 10:35 ` Andrew Cooper
2018-10-02 10:16 ` [PATCH v4 08/12] cpufreq: convert to a single post-init driver (hooks) instance Jan Beulich
2018-10-04 10:36 ` Andrew Cooper
2018-10-02 10:16 ` [PATCH v4 09/12] cpufreq: patch target() indirect call to direct one Jan Beulich
2018-10-04 10:36 ` Andrew Cooper
2018-10-02 10:18 ` [PATCH v4 10/12] IOMMU: introduce IOMMU_MIXED config option Jan Beulich
2018-10-02 10:38 ` Julien Grall
2018-10-02 10:42 ` Jan Beulich
2018-10-02 11:00 ` Julien Grall
2018-10-02 11:58 ` Jan Beulich
2018-10-02 12:58 ` Julien Grall
2018-11-06 15:48 ` Jan Beulich
2018-11-07 18:01 ` Julien Grall
2018-10-02 10:18 ` [PATCH v4 11/12] IOMMU: remove indirection from certain IOMMU hook accesses Jan Beulich
2018-10-02 10:19 ` [PATCH v4 12/12] IOMMU: patch certain indirect calls to direct ones Jan Beulich
2018-11-08 15:56 ` [PATCH v5 00/13] x86: indirect call overhead reduction Jan Beulich
2018-11-08 16:05 ` [PATCH v5 01/13] x86: reduce general stack alignment to 8 Jan Beulich
2018-11-29 14:54 ` Wei Liu
2018-11-29 15:03 ` Jan Beulich
2018-11-29 17:44 ` Wei Liu
2018-11-30 9:03 ` Jan Beulich
2018-12-03 11:29 ` Wei Liu
2018-11-08 16:06 ` [PATCH v5 02/13] x86: clone Linux'es ASM_CALL_CONSTRAINT Jan Beulich
2018-11-29 17:13 ` Wei Liu
2018-11-08 16:08 ` [PATCH v5 03/13] x86: infrastructure to allow converting certain indirect calls to direct ones Jan Beulich
2018-11-12 10:36 ` Jan Beulich
2018-11-08 16:09 ` [PATCH v5 04/13] x86/HVM: patch indirect calls through hvm_funcs " Jan Beulich
2018-11-08 16:09 ` [PATCH v5 05/13] x86/HVM: patch vINTR " Jan Beulich
2018-11-08 16:10 ` [PATCH v5 06/13] x86: patch ctxt_switch_masking() indirect call to direct one Jan Beulich
2018-11-08 16:11 ` [PATCH v5 07/13] x86/genapic: patch indirect calls to direct ones Jan Beulich
2018-11-08 16:11 ` [PATCH v5 08/13] x86/cpuidle: patch some " Jan Beulich
2018-11-08 16:12 ` [PATCH v5 09/13] cpufreq: convert to a single post-init driver (hooks) instance Jan Beulich
2018-11-08 16:13 ` [PATCH v5 10/13] cpufreq: patch target() indirect call to direct one Jan Beulich
2018-11-08 16:14 ` [PATCH v5 11/13] IOMMU: move inclusion point of asm/iommu.h Jan Beulich
2018-11-12 11:55 ` Julien Grall
2018-11-08 16:16 ` [PATCH v5 12/13] IOMMU/x86: remove indirection from certain IOMMU hook accesses Jan Beulich
2018-11-14 3:25 ` Tian, Kevin
2018-11-14 17:16 ` Woods, Brian
2018-11-08 16:17 ` [PATCH v5 13/13] IOMMU: patch certain indirect calls to direct ones Jan Beulich
2018-11-29 14:49 ` Wei Liu
2018-12-05 15:54 ` [PATCH v6 00/10] x86: indirect call overhead reduction Jan Beulich
2018-12-05 16:02 ` [PATCH v6 01/10] x86: reduce general stack alignment to 8 Jan Beulich
2018-12-05 16:02 ` [PATCH v6 02/10] x86: clone Linux'es ASM_CALL_CONSTRAINT Jan Beulich
2018-12-05 16:03 ` [PATCH v6 03/10] x86: infrastructure to allow converting certain indirect calls to direct ones Jan Beulich
2018-12-05 16:04 ` [PATCH v6 04/10] x86/HVM: patch indirect calls through hvm_funcs " Jan Beulich
2018-12-05 16:05 ` [PATCH v6 05/10] x86/HVM: patch vINTR " Jan Beulich
2018-12-05 16:06 ` [PATCH v6 06/10] x86: patch ctxt_switch_masking() indirect call to direct one Jan Beulich
2018-12-05 16:06 ` [PATCH v6 07/10] x86/genapic: patch indirect calls to direct ones Jan Beulich
2018-12-05 16:07 ` [PATCH v6 08/10] x86/cpuidle: patch some " Jan Beulich
2018-12-05 16:07 ` [PATCH v6 09/10] cpufreq: patch target() indirect call to direct one Jan Beulich
2018-12-05 16:08 ` [PATCH v6 10/10] IOMMU: patch certain indirect calls to direct ones Jan Beulich
[not found] ` <5C07F49D0200000000101036@prv1-mh.provo.novell.com>
[not found] ` <5C07F49D020000780021DC1A@prv1-mh.provo.novell.com>
2019-03-12 13:59 ` [PATCH v7 00/10] x86: indirect call overhead reduction Jan Beulich
2019-03-12 14:03 ` Jan Beulich [this message]
2019-03-12 14:04 ` [PATCH v7 02/10] x86: clone Linux'es ASM_CALL_CONSTRAINT Jan Beulich
2019-03-12 14:05 ` [PATCH v7 03/10] x86: infrastructure to allow converting certain indirect calls to direct ones Jan Beulich
2019-03-12 14:06 ` [PATCH v7 04/10] x86/HVM: patch indirect calls through hvm_funcs " Jan Beulich
2019-03-12 14:06 ` [PATCH v7 05/10] x86/HVM: patch vINTR " Jan Beulich
2019-03-12 14:07 ` [PATCH v7 06/10] x86: patch ctxt_switch_masking() indirect call to direct one Jan Beulich
2019-03-12 14:07 ` [PATCH v7 07/10] x86/genapic: patch indirect calls to direct ones Jan Beulich
2019-03-12 14:08 ` [PATCH v7 08/10] x86/cpuidle: patch some " Jan Beulich
2019-03-12 14:08 ` [PATCH v7 09/10] cpufreq: patch target() indirect call to direct one Jan Beulich
2019-03-12 14:09 ` [PATCH v7 10/10] IOMMU: patch certain indirect calls to direct ones Jan Beulich
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