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Groups > linux.kernel > #1538633 > unrolled thread
| Started by | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| First post | 2016-12-08 16:50 +0100 |
| Last post | 2016-12-12 08:00 +0100 |
| Articles | 7 — 3 participants |
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[PATCH 0/2] Fix paravirt fail Peter Zijlstra <peterz@infradead.org> - 2016-12-08 16:50 +0100
[PATCH 1/2] x86,paravirt: Fix native_patch() Peter Zijlstra <peterz@infradead.org> - 2016-12-08 16:50 +0100
[tip:locking/core] x86/paravirt: Fix native_patch() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2016-12-12 08:00 +0100
[PATCH 2/2] x86, paravirt: Fix bool return type for PVOP_CALL Peter Zijlstra <peterz@infradead.org> - 2016-12-08 16:50 +0100
Re: [PATCH 2/2] x86, paravirt: Fix bool return type for PVOP_CALL Pan Xinhui <xinhui@linux.vnet.ibm.com> - 2016-12-08 17:50 +0100
Re: [PATCH 2/2] x86, paravirt: Fix bool return type for PVOP_CALL Peter Zijlstra <peterz@infradead.org> - 2016-12-08 18:00 +0100
[tip:locking/core] x86/paravirt: Fix bool return type for PVOP_CALL() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2016-12-12 08:00 +0100
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2016-12-08 16:50 +0100 |
| Subject | [PATCH 0/2] Fix paravirt fail |
| Message-ID | <sM97k-7Se-15@gated-at.bofh.it> |
Two patches that cure fallout from commit:
3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
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| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2016-12-08 16:50 +0100 |
| Subject | [PATCH 1/2] x86,paravirt: Fix native_patch() |
| Message-ID | <sM97k-7Se-51@gated-at.bofh.it> |
| In reply to | #1538633 |
While chasing a regression I noticed we potentially patch the wrong
code in native_patch().
If we do not select the native code sequence, we must use the default
patcher, not fall-through the switch case.
Fixes: 3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kernel/paravirt_patch_32.c | 4 ++++
arch/x86/kernel/paravirt_patch_64.c | 4 ++++
2 files changed, 8 insertions(+)
--- a/arch/x86/kernel/paravirt_patch_32.c
+++ b/arch/x86/kernel/paravirt_patch_32.c
@@ -56,15 +56,19 @@ unsigned native_patch(u8 type, u16 clobb
end = end_pv_lock_ops_queued_spin_unlock;
goto patch_site;
}
+ goto patch_default;
+
case PARAVIRT_PATCH(pv_lock_ops.vcpu_is_preempted):
if (pv_is_native_vcpu_is_preempted()) {
start = start_pv_lock_ops_vcpu_is_preempted;
end = end_pv_lock_ops_vcpu_is_preempted;
goto patch_site;
}
+ goto patch_default;
#endif
default:
+patch_default:
ret = paravirt_patch_default(type, clobbers, ibuf, addr, len);
break;
--- a/arch/x86/kernel/paravirt_patch_64.c
+++ b/arch/x86/kernel/paravirt_patch_64.c
@@ -68,15 +68,19 @@ unsigned native_patch(u8 type, u16 clobb
end = end_pv_lock_ops_queued_spin_unlock;
goto patch_site;
}
+ goto patch_default;
+
case PARAVIRT_PATCH(pv_lock_ops.vcpu_is_preempted):
if (pv_is_native_vcpu_is_preempted()) {
start = start_pv_lock_ops_vcpu_is_preempted;
end = end_pv_lock_ops_vcpu_is_preempted;
goto patch_site;
}
+ goto patch_default;
#endif
default:
+patch_default:
ret = paravirt_patch_default(type, clobbers, ibuf, addr, len);
break;
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| From | tip-bot for Peter Zijlstra <tipbot@zytor.com> |
|---|---|
| Date | 2016-12-12 08:00 +0100 |
| Subject | [tip:locking/core] x86/paravirt: Fix native_patch() |
| Message-ID | <sNsKB-11W-3@gated-at.bofh.it> |
| In reply to | #1538637 |
Commit-ID: 45dbea5f55c05980cbb4c30047c71a820cd3f282
Gitweb: http://git.kernel.org/tip/45dbea5f55c05980cbb4c30047c71a820cd3f282
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 8 Dec 2016 16:42:14 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 11 Dec 2016 13:09:19 +0100
x86/paravirt: Fix native_patch()
While chasing a regression I noticed we potentially patch the wrong
code in native_patch().
If we do not select the native code sequence, we must use the default
patcher, not fall-through the switch case.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel test robot <xiaolong.ye@intel.com>
Fixes: 3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
Link: http://lkml.kernel.org/r/20161208154349.270616999@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/paravirt_patch_32.c | 4 ++++
arch/x86/kernel/paravirt_patch_64.c | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c
index ff03dbd..33cdec2 100644
--- a/arch/x86/kernel/paravirt_patch_32.c
+++ b/arch/x86/kernel/paravirt_patch_32.c
@@ -58,15 +58,19 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
end = end_pv_lock_ops_queued_spin_unlock;
goto patch_site;
}
+ goto patch_default;
+
case PARAVIRT_PATCH(pv_lock_ops.vcpu_is_preempted):
if (pv_is_native_vcpu_is_preempted()) {
start = start_pv_lock_ops_vcpu_is_preempted;
end = end_pv_lock_ops_vcpu_is_preempted;
goto patch_site;
}
+ goto patch_default;
#endif
default:
+patch_default:
ret = paravirt_patch_default(type, clobbers, ibuf, addr, len);
break;
diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c
index e61dd97..b0fceff 100644
--- a/arch/x86/kernel/paravirt_patch_64.c
+++ b/arch/x86/kernel/paravirt_patch_64.c
@@ -70,15 +70,19 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
end = end_pv_lock_ops_queued_spin_unlock;
goto patch_site;
}
+ goto patch_default;
+
case PARAVIRT_PATCH(pv_lock_ops.vcpu_is_preempted):
if (pv_is_native_vcpu_is_preempted()) {
start = start_pv_lock_ops_vcpu_is_preempted;
end = end_pv_lock_ops_vcpu_is_preempted;
goto patch_site;
}
+ goto patch_default;
#endif
default:
+patch_default:
ret = paravirt_patch_default(type, clobbers, ibuf, addr, len);
break;
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| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2016-12-08 16:50 +0100 |
| Subject | [PATCH 2/2] x86, paravirt: Fix bool return type for PVOP_CALL |
| Message-ID | <sM97l-7Se-75@gated-at.bofh.it> |
| In reply to | #1538633 |
Commit 3cded4179481 ("x86/paravirt: Optimize native
pv_lock_ops.vcpu_is_preempted()") introduced a paravirt op with bool
return type [*]
It turns out that the PVOP_CALL*() macros miscompile when rettype is
bool. Code that looked like:
83 ef 01 sub $0x1,%edi
ff 15 32 a0 d8 00 callq *0xd8a032(%rip) # ffffffff81e28120 <pv_lock_ops+0x20>
84 c0 test %al,%al
ended up looking like so after PVOP_CALL1() was applied:
83 ef 01 sub $0x1,%edi
48 63 ff movslq %edi,%rdi
ff 14 25 20 81 e2 81 callq *0xffffffff81e28120
48 85 c0 test %rax,%rax
Note how it tests the whole of %rax, even though a typical bool return
function only sets %al, like:
0f 95 c0 setne %al
c3 retq
This is because ____PVOP_CALL() does:
__ret = (rettype)__eax;
and while regular integer type casts truncate the result, a cast to
bool tests for any !0 value. Fix this by explicitly truncating to
sizeof(rettype) before casting.
[*] The actual bug should've been exposed in commit 446f3dc8cc0a
("locking/core, x86/paravirt: Implement vcpu_is_preempted(cpu) for KVM
and Xen guests") but that didn't properly implement the paravirt call.
Cc: Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: virtualization@lists.linux-foundation.org
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Fixes: 3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/paravirt_types.h | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -508,6 +508,18 @@ int paravirt_disable_iospace(void);
#define PVOP_TEST_NULL(op) ((void)op)
#endif
+#define PVOP_RETMASK(rettype) \
+ ({ unsigned long __mask = ~0UL; \
+ switch (sizeof(rettype)) { \
+ case 1: __mask = 0xffUL; break; \
+ case 2: __mask = 0xffffUL; break; \
+ case 4: __mask = 0xffffffffUL; break; \
+ default: break; \
+ } \
+ __mask; \
+ })
+
+
#define ____PVOP_CALL(rettype, op, clbr, call_clbr, extra_clbr, \
pre, post, ...) \
({ \
@@ -535,7 +547,7 @@ int paravirt_disable_iospace(void);
paravirt_clobber(clbr), \
##__VA_ARGS__ \
: "memory", "cc" extra_clbr); \
- __ret = (rettype)__eax; \
+ __ret = (rettype)(__eax & PVOP_RETMASK(rettype)); \
} \
__ret; \
})
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| From | Pan Xinhui <xinhui@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-12-08 17:50 +0100 |
| Subject | Re: [PATCH 2/2] x86, paravirt: Fix bool return type for PVOP_CALL |
| Message-ID | <sMa3n-8rP-21@gated-at.bofh.it> |
| In reply to | #1538650 |
hi, Peter
I think I know the point.
then could we just let __eax rettype(here is bool), not unsigned long?
I does not do tests for my thoughts.
@@ -461,7 +461,9 @@ int paravirt_disable_iospace(void);
#define PVOP_VCALL_ARGS \
unsigned long __eax = __eax, __edx = __edx, __ecx = __ecx; \
register void *__sp asm("esp")
-#define PVOP_CALL_ARGS PVOP_VCALL_ARGS
+#define PVOP_CALL_ARGS \
+ rettype __eax = __eax, __edx = __edx, __ecx = __ecx; \
+ register void *__sp asm("esp")
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| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2016-12-08 18:00 +0100 |
| Subject | Re: [PATCH 2/2] x86, paravirt: Fix bool return type for PVOP_CALL |
| Message-ID | <sMad4-8vg-15@gated-at.bofh.it> |
| In reply to | #1538724 |
On Fri, Dec 09, 2016 at 12:40:35AM +0800, Pan Xinhui wrote:
>
> hi, Peter
> I think I know the point.
>
> then could we just let __eax rettype(here is bool), not unsigned long?
> I does not do tests for my thoughts.
>
> @@ -461,7 +461,9 @@ int paravirt_disable_iospace(void);
> #define PVOP_VCALL_ARGS \
> unsigned long __eax = __eax, __edx = __edx, __ecx = __ecx; \
> register void *__sp asm("esp")
> -#define PVOP_CALL_ARGS PVOP_VCALL_ARGS
> +#define PVOP_CALL_ARGS \
> + rettype __eax = __eax, __edx = __edx, __ecx = __ecx; \
> + register void *__sp asm("esp")
Doesn't work on i386 where eax is also an argument register.
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| From | tip-bot for Peter Zijlstra <tipbot@zytor.com> |
|---|---|
| Date | 2016-12-12 08:00 +0100 |
| Subject | [tip:locking/core] x86/paravirt: Fix bool return type for PVOP_CALL() |
| Message-ID | <sNsKB-11W-7@gated-at.bofh.it> |
| In reply to | #1538650 |
Commit-ID: 11f254dbb3a2e3f0d8552d0dd37f4faa432b6b16
Gitweb: http://git.kernel.org/tip/11f254dbb3a2e3f0d8552d0dd37f4faa432b6b16
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 8 Dec 2016 16:42:15 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 11 Dec 2016 13:09:20 +0100
x86/paravirt: Fix bool return type for PVOP_CALL()
Commit:
3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
introduced a paravirt op with bool return type [*]
It turns out that the PVOP_CALL*() macros miscompile when rettype is
bool. Code that looked like:
83 ef 01 sub $0x1,%edi
ff 15 32 a0 d8 00 callq *0xd8a032(%rip) # ffffffff81e28120 <pv_lock_ops+0x20>
84 c0 test %al,%al
ended up looking like so after PVOP_CALL1() was applied:
83 ef 01 sub $0x1,%edi
48 63 ff movslq %edi,%rdi
ff 14 25 20 81 e2 81 callq *0xffffffff81e28120
48 85 c0 test %rax,%rax
Note how it tests the whole of %rax, even though a typical bool return
function only sets %al, like:
0f 95 c0 setne %al
c3 retq
This is because ____PVOP_CALL() does:
__ret = (rettype)__eax;
and while regular integer type casts truncate the result, a cast to
bool tests for any !0 value. Fix this by explicitly truncating to
sizeof(rettype) before casting.
[*] The actual bug should've been exposed in commit:
446f3dc8cc0a ("locking/core, x86/paravirt: Implement vcpu_is_preempted(cpu) for KVM and Xen guests")
but that didn't properly implement the paravirt call.
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
Link: http://lkml.kernel.org/r/20161208154349.346057680@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/paravirt_types.h | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 2614bd7..3f2bc0f 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -510,6 +510,18 @@ int paravirt_disable_iospace(void);
#define PVOP_TEST_NULL(op) ((void)op)
#endif
+#define PVOP_RETMASK(rettype) \
+ ({ unsigned long __mask = ~0UL; \
+ switch (sizeof(rettype)) { \
+ case 1: __mask = 0xffUL; break; \
+ case 2: __mask = 0xffffUL; break; \
+ case 4: __mask = 0xffffffffUL; break; \
+ default: break; \
+ } \
+ __mask; \
+ })
+
+
#define ____PVOP_CALL(rettype, op, clbr, call_clbr, extra_clbr, \
pre, post, ...) \
({ \
@@ -537,7 +549,7 @@ int paravirt_disable_iospace(void);
paravirt_clobber(clbr), \
##__VA_ARGS__ \
: "memory", "cc" extra_clbr); \
- __ret = (rettype)__eax; \
+ __ret = (rettype)(__eax & PVOP_RETMASK(rettype)); \
} \
__ret; \
})
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