On Mon, Oct 23, 2017 at 01:37:09PM +0100, Marc Zyngier wrote:
> On Mon, Oct 23 2017 at 1:05:23 pm BST, Will Deacon <[email protected]>
> wrote:
> > Hi Marc,
> >
> > On Fri, Oct 20, 2017 at 04:48:57PM +0100, Marc Zyngier wrote:
> >> We currently tightly couple dcache clean with icache invalidation,
> >> but KVM could do without the initial flush to PoU, as we've
> >> already flushed things to PoC.
> >>
> >> Let's introduce invalidate_icache_range which is limited to
> >> invalidating the icache from the linear mapping (and thus
> >> has none of the userspace fault handling complexity), and
> >> wire it in KVM instead of flush_icache_range.
> >>
> >> Reviewed-by: Christoffer Dall <[email protected]>
> >> Signed-off-by: Marc Zyngier <[email protected]>
> >> ---
> >> arch/arm64/include/asm/assembler.h | 26 ++++++++++++++++++++++++++
> >> arch/arm64/include/asm/cacheflush.h | 8 ++++++++
> >> arch/arm64/include/asm/kvm_mmu.h | 4 ++--
> >> arch/arm64/mm/cache.S | 26 ++++++++++++++++----------
> >> 4 files changed, 52 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/arch/arm64/include/asm/assembler.h
> >> b/arch/arm64/include/asm/assembler.h
> >> index d58a6253c6ab..efdbecc8f2ef 100644
> >> --- a/arch/arm64/include/asm/assembler.h
> >> +++ b/arch/arm64/include/asm/assembler.h
> >> @@ -374,6 +374,32 @@ alternative_endif
> >> dsb \domain
> >> .endm
> >>
> >> +/*
> >> + * Macro to perform an instruction cache maintenance for the interval
> >> + * [start, end)
> >> + *
> >> + * start, end: virtual addresses describing the region
> >> + * label: A label to branch to on user fault, none if
> >> + * only used on a kernel address
> >> + * Corrupts: tmp1, tmp2
> >> + */
> >> + .macro invalidate_icache_by_line start, end, tmp1, tmp2, label=none
> >> + icache_line_size \tmp1, \tmp2
> >> + sub \tmp2, \tmp1, #1
> >> + bic \tmp2, \start, \tmp2
> >> +9997:
> >> + .if (\label == none)
> >> + ic ivau, \tmp2 // invalidate I line PoU
> >> + .else
> >> +USER(\label, ic ivau, \tmp2) // invalidate I line PoU
> >> + .endif
> >> + add \tmp2, \tmp2, \tmp1
> >> + cmp \tmp2, \end
> >> + b.lo 9997b
> >> + dsb ish
> >> + isb
> >> + .endm
> >
> > Code looks fine to me, but I'd like to drop the \label == none case. See
> > below.
> >
> >> /*
> >> * reset_pmuserenr_el0 - reset PMUSERENR_EL0 if PMUv3 present
> >> */
> >> diff --git a/arch/arm64/include/asm/cacheflush.h
> >> b/arch/arm64/include/asm/cacheflush.h
> >> index 76d1cc85d5b1..ad56406944c6 100644
> >> --- a/arch/arm64/include/asm/cacheflush.h
> >> +++ b/arch/arm64/include/asm/cacheflush.h
> >> @@ -52,6 +52,13 @@
> >> * - start - virtual start address
> >> * - end - virtual end address
> >> *
> >> + * invalidate_icache_range(start, end)
> >> + *
> >> + * Invalidate the I-cache in the region described by
> >> start, end.
> >> + * Linear mapping only!
> >> + * - start - virtual start address
> >> + * - end - virtual end address
> >> + *
> >> * __flush_cache_user_range(start, end)
> >> *
> >> * Ensure coherency between the I-cache and the D-cache in
> >> the
> >> @@ -66,6 +73,7 @@
> >> * - size - region size
> >> */
> >> extern void flush_icache_range(unsigned long start, unsigned long end);
> >> +extern void invalidate_icache_range(unsigned long start, unsigned long
> >> end);
> >> extern void __flush_dcache_area(void *addr, size_t len);
> >> extern void __inval_dcache_area(void *addr, size_t len);
> >> extern void __clean_dcache_area_poc(void *addr, size_t len);
> >> diff --git a/arch/arm64/include/asm/kvm_mmu.h
> >> b/arch/arm64/include/asm/kvm_mmu.h
> >> index 8034b96fb3a4..56b3e03c85e7 100644
> >> --- a/arch/arm64/include/asm/kvm_mmu.h
> >> +++ b/arch/arm64/include/asm/kvm_mmu.h
> >> @@ -250,8 +250,8 @@ static inline void
> >> __invalidate_icache_guest_page(struct kvm_vcpu *vcpu,
> >> /* PIPT or VPIPT at EL2 (see comment in
> >> __kvm_tlb_flush_vmid_ipa) */
> >> void *va = page_address(pfn_to_page(pfn));
> >>
> >> - flush_icache_range((unsigned long)va,
> >> - (unsigned long)va + size);
> >> + invalidate_icache_range((unsigned long)va,
> >> + (unsigned long)va + size);
> >> }
> >> }
> >>
> >> diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
> >> index 7f1dbe962cf5..8e71d237f85e 100644
> >> --- a/arch/arm64/mm/cache.S
> >> +++ b/arch/arm64/mm/cache.S
> >> @@ -60,16 +60,7 @@ user_alt 9f, "dc cvau, x4", "dc civac, x4",
> >> ARM64_WORKAROUND_CLEAN_CACHE
> >> b.lo 1b
> >> dsb ish
> >>
> >> - icache_line_size x2, x3
> >> - sub x3, x2, #1
> >> - bic x4, x0, x3
> >> -1:
> >> -USER(9f, ic ivau, x4 ) // invalidate I line PoU
> >> - add x4, x4, x2
> >> - cmp x4, x1
> >> - b.lo 1b
> >> - dsb ish
> >> - isb
> >> + invalidate_icache_by_line x0, x1, x2, x3, 9f
> >> mov x0, #0
> >> 1:
> >> uaccess_ttbr0_disable x1
> >> @@ -80,6 +71,21 @@ USER(9f, ic ivau, x4 ) //
> >> invalidate I line PoU
> >> ENDPROC(flush_icache_range)
> >> ENDPROC(__flush_cache_user_range)
> >>
> >> +/*
> >> + * invalidate_icache_range(start,end)
> >> + *
> >> + * Ensure that the I cache is invalid within specified region. This
> >> + * assumes that this is done on the linear mapping. Do not use it
> >> + * on a userspace range, as this may fault horribly.
> >
> > I'm still not sure why we're not hooking up the user fault handling here.
> > In the worst case, we'd end up returning -EFAULT if we got passed a
> > faulting user address and there's already precedence for this with e.g.
> > flush_icache_range.
>
> Fair enough. Confusingly, flush_icache_range is declared as returning
> void... I'll cook a separate patch addressing this. How about the
> following on top of that patch:
>
> diff --git a/arch/arm64/include/asm/assembler.h
> b/arch/arm64/include/asm/assembler.h
> index efdbecc8f2ef..27093cf2b91f 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -379,20 +379,15 @@ alternative_endif
> * [start, end)
> *
> * start, end: virtual addresses describing the region
> - * label: A label to branch to on user fault, none if
> - * only used on a kernel address
> + * label: A label to branch to on user fault.
> * Corrupts: tmp1, tmp2
> */
> - .macro invalidate_icache_by_line start, end, tmp1, tmp2, label=none
> + .macro invalidate_icache_by_line start, end, tmp1, tmp2, label
> icache_line_size \tmp1, \tmp2
> sub \tmp2, \tmp1, #1
> bic \tmp2, \start, \tmp2
> 9997:
> - .if (\label == none)
> - ic ivau, \tmp2 // invalidate I line PoU
> - .else
> USER(\label, ic ivau, \tmp2) // invalidate I line PoU
> - .endif
> add \tmp2, \tmp2, \tmp1
> cmp \tmp2, \end
> b.lo 9997b
> diff --git a/arch/arm64/include/asm/cacheflush.h
> b/arch/arm64/include/asm/cacheflush.h
> index ad56406944c6..e671e73c6453 100644
> --- a/arch/arm64/include/asm/cacheflush.h
> +++ b/arch/arm64/include/asm/cacheflush.h
> @@ -55,7 +55,6 @@
> * invalidate_icache_range(start, end)
> *
> * Invalidate the I-cache in the region described by start, end.
> - * Linear mapping only!
> * - start - virtual start address
> * - end - virtual end address
> *
> @@ -73,7 +72,7 @@
> * - size - region size
> */
> extern void flush_icache_range(unsigned long start, unsigned long end);
> -extern void invalidate_icache_range(unsigned long start, unsigned long end);
> +extern int invalidate_icache_range(unsigned long start, unsigned long end);
> extern void __flush_dcache_area(void *addr, size_t len);
> extern void __inval_dcache_area(void *addr, size_t len);
> extern void __clean_dcache_area_poc(void *addr, size_t len);
> diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
> index 8e71d237f85e..a89f23610b7e 100644
> --- a/arch/arm64/mm/cache.S
> +++ b/arch/arm64/mm/cache.S
> @@ -74,15 +74,17 @@ ENDPROC(__flush_cache_user_range)
> /*
> * invalidate_icache_range(start,end)
> *
> - * Ensure that the I cache is invalid within specified region. This
> - * assumes that this is done on the linear mapping. Do not use it
> - * on a userspace range, as this may fault horribly.
> + * Ensure that the I cache is invalid within specified region.
> *
> * - start - virtual start address of region
> * - end - virtual end address of region
> */
> ENTRY(invalidate_icache_range)
> - invalidate_icache_by_line x0, x1, x2, x3
> + invalidate_icache_by_line x0, x1, x2, x3, 1f
> + mov x0, xzr
> + ret
> +1:
> + mov x0, #-EFAULT
You need to add the uaccess_ttbr0_{enable,disable} calls here, but with
that then I think this is good.
Will
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