Messages in this thread Patch in this message | | | Date | Fri, 5 Nov 2021 21:58:05 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 15/22] x86,vmx: Remove .fixup usage |
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On Fri, Nov 05, 2021 at 06:17:53PM +0000, Sean Christopherson wrote:
> diff --git a/arch/x86/kvm/vmx/vmx_ops.h b/arch/x86/kvm/vmx/vmx_ops.h > index 9e9ef47e988c..5e5113d2b324 100644 > --- a/arch/x86/kvm/vmx/vmx_ops.h > +++ b/arch/x86/kvm/vmx/vmx_ops.h
> @@ -76,29 +75,24 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field) > "ja 3f\n\t" > > /* > - * VMREAD failed. Push '0' for @fault, push the failing > - * @field, and bounce through the trampoline to preserve > - * volatile registers. > + * VMREAD failed, push the failing @field, and bounce > + * through the trampoline to preserve volatile registers. > + * If VMREAD faults, this will push -FAULT (see below). > */ > - "push $0\n\t" > - "push %2\n\t" > - "2:call vmread_error_trampoline\n\t" > + "2: push %2\n\t" > + "call vmread_error_trampoline\n\t" > > /* > * Unwind the stack. Note, the trampoline zeros out the > - * memory for @fault so that the result is '0' on error. > + * memory for @field so that the result is '0' on error, > + * hence the pop to %1, not %2. > */ > - "pop %2\n\t" > "pop %1\n\t" > "3:\n\t" > > - /* VMREAD faulted. As above, except push '1' for @fault. */ > - ".pushsection .fixup, \"ax\"\n\t" > - "4: push $1\n\t" > - "push %2\n\t" > - "jmp 2b\n\t" > - ".popsection\n\t" > - _ASM_EXTABLE(1b, 4b) > + /* VMREAD faulted. As above, except push '-EFAULT' for @fault. */ > + _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %1) > + > : ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc"); > return value; > }
A different option is something like the below; down side is that it increases the amount of text, while your version decreases the amount of useless text (the gunk between vmread and 3:, all of which should ideally live out-of-line).
For now I'll stick with your patch.
diff --git a/arch/x86/kvm/vmx/vmx_ops.h b/arch/x86/kvm/vmx/vmx_ops.h index 9e9ef47e988c..99fc1f34fbd4 100644 --- a/arch/x86/kvm/vmx/vmx_ops.h +++ b/arch/x86/kvm/vmx/vmx_ops.h @@ -81,8 +81,8 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field) * volatile registers. */ "push $0\n\t" - "push %2\n\t" - "2:call vmread_error_trampoline\n\t" + "2: push %2\n\t" + "call vmread_error_trampoline\n\t" /* * Unwind the stack. Note, the trampoline zeros out the @@ -90,14 +90,14 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field) */ "pop %2\n\t" "pop %1\n\t" - "3:\n\t" + "jmp 3f\n\t" - /* VMREAD faulted. As above, except push '1' for @fault. */ - ".pushsection .fixup, \"ax\"\n\t" "4: push $1\n\t" - "push %2\n\t" "jmp 2b\n\t" - ".popsection\n\t" + + "3:\n\t" + + /* VMREAD faulted. As above, except push '1' for @fault. */ _ASM_EXTABLE(1b, 4b) : ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc"); return value;
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