* mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
@ 2022-07-13 11:28 Sudip Mukherjee (Codethink)
2022-07-13 11:35 ` Peter Zijlstra
0 siblings, 1 reply; 4+ messages in thread
From: Sudip Mukherjee (Codethink) @ 2022-07-13 11:28 UTC (permalink / raw)
To: Josh Poimboeuf, Peter Zijlstra, Borislav Petkov
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Paolo Bonzini, Sean Christopherson,
Vitaly Kuznetsov, Wanpeng Li, Jim Mattson, Joerg Roedel,
linux-kernel, kvm, Linus Torvalds
Hi All,
The latest mainline kernel branch fails to build for x86_64 allmodconfig
with clang and the error is:
arch/x86/kernel/cpu/bugs.c:58:21: error: section attribute is specified on redeclared variable [-Werror,-Wsection]
DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
^
./arch/x86/include/asm/nospec-branch.h:283:12: note: previous declaration is here
extern u64 x86_spec_ctrl_current;
git bisect pointed to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
I will be happy to test any patch or provide any extra log if needed.
--
Regards
Sudip
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
2022-07-13 11:28 mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS") Sudip Mukherjee (Codethink)
@ 2022-07-13 11:35 ` Peter Zijlstra
2022-07-13 12:22 ` Peter Zijlstra
0 siblings, 1 reply; 4+ messages in thread
From: Peter Zijlstra @ 2022-07-13 11:35 UTC (permalink / raw)
To: Sudip Mukherjee (Codethink)
Cc: Josh Poimboeuf, Borislav Petkov, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Paolo Bonzini,
Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, linux-kernel, kvm, Linus Torvalds
On Wed, Jul 13, 2022 at 12:28:38PM +0100, Sudip Mukherjee (Codethink) wrote:
> Hi All,
>
> The latest mainline kernel branch fails to build for x86_64 allmodconfig
> with clang and the error is:
>
> arch/x86/kernel/cpu/bugs.c:58:21: error: section attribute is specified on redeclared variable [-Werror,-Wsection]
> DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
> ^
> ./arch/x86/include/asm/nospec-branch.h:283:12: note: previous declaration is here
> extern u64 x86_spec_ctrl_current;
>
>
> git bisect pointed to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
>
> I will be happy to test any patch or provide any extra log if needed.
I suspect something like this will do.
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index bb05ed4f46bd..6398d39e66b0 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -280,7 +280,7 @@ static inline void indirect_branch_prediction_barrier(void)
/* The Intel SPEC CTRL MSR base value cache */
extern u64 x86_spec_ctrl_base;
-extern u64 x86_spec_ctrl_current;
+DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
extern void write_spec_ctrl_current(u64 val, bool force);
extern u64 spec_ctrl_current(void);
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
2022-07-13 11:35 ` Peter Zijlstra
@ 2022-07-13 12:22 ` Peter Zijlstra
2022-07-13 13:34 ` Sudip Mukherjee
0 siblings, 1 reply; 4+ messages in thread
From: Peter Zijlstra @ 2022-07-13 12:22 UTC (permalink / raw)
To: Sudip Mukherjee (Codethink)
Cc: Josh Poimboeuf, Borislav Petkov, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Paolo Bonzini,
Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, linux-kernel, kvm, Linus Torvalds
On Wed, Jul 13, 2022 at 01:35:22PM +0200, Peter Zijlstra wrote:
> On Wed, Jul 13, 2022 at 12:28:38PM +0100, Sudip Mukherjee (Codethink) wrote:
> > Hi All,
> >
> > The latest mainline kernel branch fails to build for x86_64 allmodconfig
> > with clang and the error is:
> >
> > arch/x86/kernel/cpu/bugs.c:58:21: error: section attribute is specified on redeclared variable [-Werror,-Wsection]
> > DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
> > ^
> > ./arch/x86/include/asm/nospec-branch.h:283:12: note: previous declaration is here
> > extern u64 x86_spec_ctrl_current;
> >
> >
> > git bisect pointed to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
> >
> > I will be happy to test any patch or provide any extra log if needed.
>
> I suspect something like this will do.
>
> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
> index bb05ed4f46bd..6398d39e66b0 100644
> --- a/arch/x86/include/asm/nospec-branch.h
> +++ b/arch/x86/include/asm/nospec-branch.h
> @@ -280,7 +280,7 @@ static inline void indirect_branch_prediction_barrier(void)
>
> /* The Intel SPEC CTRL MSR base value cache */
> extern u64 x86_spec_ctrl_base;
> -extern u64 x86_spec_ctrl_current;
> +DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
> extern void write_spec_ctrl_current(u64 val, bool force);
> extern u64 spec_ctrl_current(void);
>
I hate headers...
---
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index bb05ed4f46bd..cbc3b8348939 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -280,7 +280,6 @@ static inline void indirect_branch_prediction_barrier(void)
/* The Intel SPEC CTRL MSR base value cache */
extern u64 x86_spec_ctrl_base;
-extern u64 x86_spec_ctrl_current;
extern void write_spec_ctrl_current(u64 val, bool force);
extern u64 spec_ctrl_current(void);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index be7c19374fdd..b64512978534 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6831,6 +6831,8 @@ void noinstr vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
}
}
+DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
+
void noinstr vmx_spec_ctrl_restore_host(struct vcpu_vmx *vmx,
unsigned int flags)
{
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
2022-07-13 12:22 ` Peter Zijlstra
@ 2022-07-13 13:34 ` Sudip Mukherjee
0 siblings, 0 replies; 4+ messages in thread
From: Sudip Mukherjee @ 2022-07-13 13:34 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Josh Poimboeuf, Borislav Petkov, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Paolo Bonzini,
Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, linux-kernel, kvm, Linus Torvalds
On Wed, Jul 13, 2022 at 1:22 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Wed, Jul 13, 2022 at 01:35:22PM +0200, Peter Zijlstra wrote:
> > On Wed, Jul 13, 2022 at 12:28:38PM +0100, Sudip Mukherjee (Codethink) wrote:
> > > Hi All,
> > >
> > > The latest mainline kernel branch fails to build for x86_64 allmodconfig
> > > with clang and the error is:
> > >
<snip>
> > extern u64 spec_ctrl_current(void);
> >
>
> I hate headers...
very short commit message :D
>
> ---
> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
> index bb05ed4f46bd..cbc3b8348939 100644
> --- a/arch/x86/include/asm/nospec-branch.h
> +++ b/arch/x86/include/asm/nospec-branch.h
> @@ -280,7 +280,6 @@ static inline void indirect_branch_prediction_barrier(void)
>
> /* The Intel SPEC CTRL MSR base value cache */
> extern u64 x86_spec_ctrl_base;
> -extern u64 x86_spec_ctrl_current;
> extern void write_spec_ctrl_current(u64 val, bool force);
> extern u64 spec_ctrl_current(void);
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index be7c19374fdd..b64512978534 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6831,6 +6831,8 @@ void noinstr vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
> }
> }
>
> +DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
> +
> void noinstr vmx_spec_ctrl_restore_host(struct vcpu_vmx *vmx,
> unsigned int flags)
> {
The build failure is fixed with this change. Thanks.
--
Regards
Sudip
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-07-13 11:28 mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS") Sudip Mukherjee (Codethink)
2022-07-13 11:35 ` Peter Zijlstra
2022-07-13 12:22 ` Peter Zijlstra
2022-07-13 13:34 ` Sudip Mukherjee
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