Subject: [PATCH V2] arm64: tlbflush: avoid writing RES0 bits

From: [email-masked] (Will Deacon)
Date: Tue, 27 Mar 2018 18:36:13 +0100

Hi Shanker,

On Tue, Mar 27, 2018 at 09:53:16AM -0500, Shanker Donthineni wrote:
> On 03/27/2018 06:34 AM, Robin Murphy wrote:
> > On 27/03/18 04:21, Philip Elcan wrote:
> >> Several of the bits of the TLBI register operand are RES0 per the ARM
> >> ARM, so TLBI operations should avoid writing non-zero values to these
> >> bits.
> >>
> >> This patch adds a macro __TLBI_VADDR(addr, asid) that creates the
> >> operand register in the correct format and honors the RES0 bits.
> >>
> >> Signed-off-by: Philip Elcan <[email-masked]>
> >> ---
> >> ? arch/arm64/include/asm/tlbflush.h | 23 ++++++++++++++++-------
> >> ? 1 file changed, 16 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> >> index 9e82dd7..b1205e9 100644
> >> --- a/arch/arm64/include/asm/tlbflush.h
> >> +++ b/arch/arm64/include/asm/tlbflush.h
> >> @@ -60,6 +60,15 @@
> >> ????????? __tlbi(op, (arg) | USER_ASID_FLAG);??????????????? \
> >> ? } while (0)
> >> ? +/* This macro creates a properly formatted VA operand for the TLBI */
> >> +#define __TLBI_VADDR(addr, asid)??????????????? \
> >> +??? ({??????????????????????????? \
> >> +??????? unsigned long __ta = (addr) >> 12;??????? \
> >> +??????? __ta &= GENMASK_ULL(43, 0);??????????? \
> >> +??????? __ta |= (unsigned long)(asid) << 48;??????? \
> >> +??????? __ta;??????????????????????? \
> >> +??? })
> > 
> > I'd be inclined to make this a static inline function rather than a
> > macro, since it doesn't need to do any wacky type-dodging, but either
> > way the overall change now looks appropriate;
> > 
> > Acked-by: Robin Murphy <[email-masked]>
> > 
> 
> Tested-by: Shanker Donthineni <[email-masked]>

[...]

> >> @@ -154,8 +163,8 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma,
> >> ????????? return;
> >> ????? }
> >> ? -??? start = asid | (start >> 12);
> >> -??? end = asid | (end >> 12);
> >> +??? start = __TLBI_VADDR(start, asid);
> >> +??? end = __TLBI_VADDR(end, asid);

Can you test this bit too, please? ;)

Will