Messages in this thread Patch in this message | | | From | Herbert Xu <> | Subject | Re: [PATCH 4/5] KVM: Fix asm constraints with CONFIG_FRAME_POINTER=n | Date | Tue, 23 Jan 2007 14:10:00 +1100 |
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Avi Kivity <avi@qumranet.com> wrote: > A "g" constraint may place a local variable in an %rsp-relative memory operand. > but if your assembly changes %rsp, the operand points to the wrong location. > > An "r" constraint fixes that. > > Thanks to Ingo Molnar for neatly bisecting the problem. > > Signed-off-by: Avi Kivity <avi@qumranet.com> > > Index: linux-2.6/drivers/kvm/vmx.c > =================================================================== > --- linux-2.6.orig/drivers/kvm/vmx.c > +++ linux-2.6/drivers/kvm/vmx.c > @@ -1825,7 +1825,7 @@ again: > #endif > "setbe %0 \n\t" > "popf \n\t" > - : "=g" (fail) > + : "=r" (fail) > : "r"(vcpu->launched), "d"((unsigned long)HOST_RSP), > "c"(vcpu), > [rax]"i"(offsetof(struct kvm_vcpu, regs[VCPU_REGS_RAX])),
We need the following fix for 2.6.20.
[KVM] vmx: Fix register constraint in launch code
Both "=r" and "=g" breaks my build on i386:
$ make CC [M] drivers/kvm/vmx.o {standard input}: Assembler messages: {standard input}:3318: Error: bad register name `%sil' make[1]: *** [drivers/kvm/vmx.o] Error 1 make: *** [_module_drivers/kvm] Error 2
The reason is that setbe requires an 8-bit register but "=r" does not constrain the target register to be one that has an 8-bit version on i386.
According to
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10153
the correct constraint is "=q".
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c index ce219e3..0aa2659 100644 --- a/drivers/kvm/vmx.c +++ b/drivers/kvm/vmx.c @@ -1824,7 +1824,7 @@ again: #endif "setbe %0 \n\t" "popf \n\t" - : "=g" (fail) + : "=q" (fail) : "r"(vcpu->launched), "d"((unsigned long)HOST_RSP), "c"(vcpu), [rax]"i"(offsetof(struct kvm_vcpu, regs[VCPU_REGS_RAX])), - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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