[PATCH v2 3/6] arm64: KVM: Avoid marking pages as XN in Stage-2 if CTR_EL0.DIC is set

Mark Rutland
2018-05-31T11:52:49Z

On Wed, May 30, 2018 at 01:47:03PM +0100, Marc Zyngier wrote:
> On systems where CTR_EL0.DIC is set, we don't need to perform
> icache invalidation to guarantee that we'll fetch the right
> instruction stream.
>
> This also means that taking a permission fault to invalidate the
> icache is an unnecessary overhead.
>
> On such systems, we can safely leave the page as being executable.
>
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
> arch/arm64/include/asm/pgtable-prot.h | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
> index c66c3047400e..78b942c1bea4 100644
> --- a/arch/arm64/include/asm/pgtable-prot.h
> +++ b/arch/arm64/include/asm/pgtable-prot.h
> @@ -77,8 +77,18 @@
> __val; \
> })
>
> -#define PAGE_S2 __pgprot(_PROT_DEFAULT | PAGE_S2_MEMATTR(NORMAL) | PTE_S2_RDONLY | PTE_S2_XN)
> -#define PAGE_S2_DEVICE __pgprot(_PROT_DEFAULT | PAGE_S2_MEMATTR(DEVICE_nGnRE) | PTE_S2_RDONLY | PTE_S2_XN)
> +#define PAGE_S2_XN \
> + ({ \
> + u64 __val; \
> + if (cpus_have_const_cap(ARM64_HAS_CACHE_DIC)) \
> + __val = 0; \
> + else \
> + __val = PTE_S2_XN; \
> + __val; \
> + })
> +
> +#define PAGE_S2 __pgprot(_PROT_DEFAULT | PAGE_S2_MEMATTR(NORMAL) | PTE_S2_RDONLY | PAGE_S2_XN)
> +#define PAGE_S2_DEVICE __pgprot(_PROT_DEFAULT | PAGE_S2_MEMATTR(DEVICE_nGnRE) | PTE_S2_RDONLY | PAGE_S2_XN)
>
> #define PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_VALID) | PTE_PROT_NONE | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN)
> #define PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
> --
> 2.17.1
>