| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Mon, 23 Mar 2009 23:14:29 -0700
From: Ravikiran G Thirumalai <kiran@...lex86.org>
To: Ingo Molnar <mingo@...e.hu>
Cc: Yinghai Lu <yinghai@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
shai@...lex86.org
Subject: Re: [PATCH] x86: don't compile vsmp_64 for 32bit
On Sun, Mar 22, 2009 at 01:48:18PM +0100, Ingo Molnar wrote:
>
>* Ravikiran G Thirumalai <kiran@...lex86.org> wrote:
>
>> On Sat, Feb 28, 2009 at 10:44:30AM +0100, Ingo Molnar wrote:
>> >
>> >* Ravikiran G Thirumalai <kiran@...lex86.org> wrote:
>> >
>> >>
>> >> True, but by how much? 212 bytes, out of 7285943 bytes which
>> >> is very very small percentage wise.
>> >
>> >How does this eliminate the validity of the patch?
>> >
>>
>> It costs 212 bytes to leave is_vsmp_box() to not just be a dummy
>> no-op. Having is_vsmp_box() detect if the hardware is indeed vSMP,
>> is meaningful even when CONFIG_VSMP is not turned on. This is
>> because is_vsmp_box() is used to tell the kernel, that although
>> the cpus being used are supposed to have TSCs in sync, they are
>> not really in sync. This is because you cannot ensure TSCs won't
>> drift between multiple boards being aggregated on vSMP systems.
>> Take the case of distro kernels. Distro kernels typically do not
>> have CONFIG_X86_VSMP on. Due to the large internode cacheline
>> setting, CONFIG_VSMP would not be on on the generic distro
>> installer kernels. If is_vsmp_box() is a no-op, the generic distro
>> installer kernels will assume TSCs to be synched, which is bad.
>> Hence, it will be nice if, for the cost of 212 bytes, vsmp64.o be
>> compiled either unconditionally, OR conditionally for 64bit
>> architectures only. The question is, is 212 bytes out of 7285943
>> bytes too expensive for the generic kernels? I hope not.
>
>Sorry - got distracted and forgot about this thread. The TSC quirk
>indeed looks required for your systems - you dont have a reliable
>TSC due to virtualization, right?
>
Yes. Also, because there is no way to avoid tsc drift on
multiple boards/nodes.
>Mind sending a patch (partial revert or so) against latest -tip that
>fixes that?
>
Sure. Here's a revert, it is a partial revert which compiles vsmp64.c only
for 64bit architectures.
Thanks,
Kiran
Partial revert of commit 129d8bc828e011bda0b7110a097bf3a0167f966e
titled 'x86: don't compile vsmp_64 for 32bit'
Commit reverted to compile vsmp_64.c if CONFIG_X86_64 is defined,
since is_vsmp_box() needs to indicate that TSCs are not synchronized, and
hence, not a valid time source, even when CONFIG_X86_VSMP is not defined.
Signed-off-by: Ravikiran Thirumalai <kiran@...lex86.org>
Index: git.tip/arch/x86/include/asm/apic.h
===================================================================
--- git.tip.orig/arch/x86/include/asm/apic.h 2009-03-23 12:50:37.000000000 -0800
+++ git.tip/arch/x86/include/asm/apic.h 2009-03-23 20:21:02.000000000 -0800
@@ -75,7 +75,7 @@ static inline void default_inquire_remot
#define setup_secondary_clock setup_secondary_APIC_clock
#endif
-#ifdef CONFIG_X86_VSMP
+#ifdef CONFIG_X86_64
extern int is_vsmp_box(void);
#else
static inline int is_vsmp_box(void)
Index: git.tip/arch/x86/include/asm/setup.h
===================================================================
--- git.tip.orig/arch/x86/include/asm/setup.h 2009-03-23 12:50:37.000000000 -0800
+++ git.tip/arch/x86/include/asm/setup.h 2009-03-23 20:19:18.000000000 -0800
@@ -64,7 +64,7 @@ extern void x86_quirk_time_init(void);
#include <asm/bootparam.h>
/* Interrupt control for vSMPowered x86_64 systems */
-#ifdef CONFIG_X86_VSMP
+#ifdef CONFIG_X86_64
void vsmp_init(void);
#else
static inline void vsmp_init(void) { }
Index: git.tip/arch/x86/kernel/Makefile
===================================================================
--- git.tip.orig/arch/x86/kernel/Makefile 2009-03-23 12:50:37.000000000 -0800
+++ git.tip/arch/x86/kernel/Makefile 2009-03-23 20:29:34.000000000 -0800
@@ -71,7 +71,6 @@ obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.
obj-$(CONFIG_KEXEC) += machine_kexec_$(BITS).o
obj-$(CONFIG_KEXEC) += relocate_kernel_$(BITS).o crash.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
-obj-$(CONFIG_X86_VSMP) += vsmp_64.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_MODULES) += module_$(BITS).o
obj-$(CONFIG_EFI) += efi.o efi_$(BITS).o efi_stub_$(BITS).o
@@ -121,4 +120,5 @@ ifeq ($(CONFIG_X86_64),y)
obj-$(CONFIG_AMD_IOMMU) += amd_iommu_init.o amd_iommu.o
obj-$(CONFIG_PCI_MMCONFIG) += mmconf-fam10h_64.o
+ obj-y += vsmp_64.o
endif
Index: git.tip/arch/x86/kernel/vsmp_64.c
===================================================================
--- git.tip.orig/arch/x86/kernel/vsmp_64.c 2009-03-23 12:50:37.000000000 -0800
+++ git.tip/arch/x86/kernel/vsmp_64.c 2009-03-23 21:09:34.000000000 -0800
@@ -22,7 +22,7 @@
#include <asm/paravirt.h>
#include <asm/setup.h>
-#ifdef CONFIG_PARAVIRT
+#if defined CONFIG_PCI && defined CONFIG_PARAVIRT
/*
* Interrupt control on vSMPowered systems:
* ~AC is a shadow of IF. If IF is 'on' AC should be 'off'
@@ -114,6 +114,7 @@ static void __init set_vsmp_pv_ops(void)
}
#endif
+#ifdef CONFIG_PCI
static int is_vsmp = -1;
static void __init detect_vsmp_box(void)
@@ -139,6 +140,15 @@ int is_vsmp_box(void)
}
}
+#else
+static void __init detect_vsmp_box(void)
+{
+}
+int is_vsmp_box(void)
+{
+ return 0;
+}
+#endif
void __init vsmp_init(void)
{
detect_vsmp_box();
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists