| Message ID | 20210603183347.1695-3-will@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kvm/arm64: Initial pKVM user ABI | expand |
On Thu, Jun 03, 2021 at 07:33:45PM +0100, Will Deacon wrote: > has_vhe() expands to a compile-time constant when evaluated from the VHE > or nVHE code, alternatively checking a static key when called from > elsewhere in the kernel. On face value, this looks like a case of > premature optimization, but in fact this allows symbol references on > VHE-specific code paths to be dropped from the nVHE object. > > Expand the comment in has_vhe() to make this clearer, hopefully > discouraging anybody from simplifying the code. > > Cc: David Brazdil <dbrazdil@google.com> > Signed-off-by: Will Deacon <will@kernel.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/include/asm/virt.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h > index 7379f35ae2c6..3218ca17f819 100644 > --- a/arch/arm64/include/asm/virt.h > +++ b/arch/arm64/include/asm/virt.h > @@ -111,6 +111,9 @@ static __always_inline bool has_vhe(void) > /* > * Code only run in VHE/NVHE hyp context can assume VHE is present or > * absent. Otherwise fall back to caps. > + * This allows the compiler to discard VHE-specific code from the > + * nVHE object, reducing the number of external symbol references > + * needed to link. > */ > if (is_vhe_hyp_code()) > return true; > -- > 2.32.0.rc0.204.g9fa02ecfa5-goog >
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h index 7379f35ae2c6..3218ca17f819 100644 --- a/arch/arm64/include/asm/virt.h +++ b/arch/arm64/include/asm/virt.h @@ -111,6 +111,9 @@ static __always_inline bool has_vhe(void) /* * Code only run in VHE/NVHE hyp context can assume VHE is present or * absent. Otherwise fall back to caps. + * This allows the compiler to discard VHE-specific code from the + * nVHE object, reducing the number of external symbol references + * needed to link. */ if (is_vhe_hyp_code()) return true;
has_vhe() expands to a compile-time constant when evaluated from the VHE or nVHE code, alternatively checking a static key when called from elsewhere in the kernel. On face value, this looks like a case of premature optimization, but in fact this allows symbol references on VHE-specific code paths to be dropped from the nVHE object. Expand the comment in has_vhe() to make this clearer, hopefully discouraging anybody from simplifying the code. Cc: David Brazdil <dbrazdil@google.com> Signed-off-by: Will Deacon <will@kernel.org> --- arch/arm64/include/asm/virt.h | 3 +++ 1 file changed, 3 insertions(+)