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Re: [Qemu-devel] [PATCH 1/3] tcg: Support MMU protection regions smaller

From: Max Filippov
Subject: Re: [Qemu-devel] [PATCH 1/3] tcg: Support MMU protection regions smaller than TARGET_PAGE_SIZE
Date: Sat, 30 Jun 2018 12:20:24 -0700

Hi Peter,

On Wed, Jun 20, 2018 at 6:06 AM, Peter Maydell <address@hidden> wrote:
> Add support for MMU protection regions that are smaller than
> TARGET_PAGE_SIZE. We do this by marking the TLB entry for those
> pages with a flag TLB_RECHECK. This flag causes us to always
> take the slow-path for accesses. In the slow path we can then
> special case them to always call tlb_fill() again, so we have
> the correct information for the exact address being accessed.
> This change allows us to handle reading and writing from small
> regions; we cannot deal with execution from the small region.
> Signed-off-by: Peter Maydell <address@hidden>
> ---
>  accel/tcg/softmmu_template.h |  24 ++++---
>  include/exec/cpu-all.h       |   5 +-
>  accel/tcg/cputlb.c           | 131 +++++++++++++++++++++++++++++------
>  3 files changed, 130 insertions(+), 30 deletions(-)

I'm observing the following failure with xtensa tests:

(qemu) qemu: fatal: Unable to handle guest executing from RAM within a
small MPU region at 0xd0000804

Bisection points to this patch. Any idea what happened?

-- Max

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