[OE-core] [PATCH] qemu: fix qemuarm64 intermediate kernel hang in raid6_select_algo func

[Burton, Ross]

An early winner of Patch of the Day in my books.

Thanks Victor!

Ross

On 26 March 2018 at 06:42, Victor Kamensky <kamensky at cisco.com> wrote:
> Backport fix from qemu mainline for intermediate qemuarm64 hang
> issue. Root caused in OE environment, issue with aarch64 qemu
> logic of executing instructions that reenabe interrupts. See patch
> commit message for more details.
>
> Upstream-Status: Backport
> Signed-off-by: Victor Kamensky <kamensky at cisco.com>
> ---
>  ...te-a64-treat-DISAS_UPDATE-as-variant-of-D.patch | 67 ++++++++++++++++++++++
>  1 file changed, 67 insertions(+)
>  create mode 100644 meta/recipes-devtools/qemu/qemu/0001-arm-translate-a64-treat-DISAS_UPDATE-as-variant-of-D.patch
>
> diff --git a/meta/recipes-devtools/qemu/qemu/0001-arm-translate-a64-treat-DISAS_UPDATE-as-variant-of-D.patch b/meta/recipes-devtools/qemu/qemu/0001-arm-translate-a64-treat-DISAS_UPDATE-as-variant-of-D.patch
> new file mode 100644
> index 0000000..f90cae6
> --- /dev/null
> +++ b/meta/recipes-devtools/qemu/qemu/0001-arm-translate-a64-treat-DISAS_UPDATE-as-variant-of-D.patch
> @@ -0,0 +1,67 @@
> +From a75a52d62418dafe462be4fe30485501d1010bb9 Mon Sep 17 00:00:00 2001
> +From: Victor Kamensky <kamensky at cisco.com>
> +Date: Fri, 23 Mar 2018 18:26:45 +0000
> +Subject: [PATCH] arm/translate-a64: treat DISAS_UPDATE as variant of
> + DISAS_EXIT
> +MIME-Version: 1.0
> +Content-Type: text/plain; charset=UTF-8
> +Content-Transfer-Encoding: 8bit
> +
> +In OE project 4.15 linux kernel boot hang was observed under
> +single cpu aarch64 qemu. Kernel code was in a loop waiting for
> +vtimer arrival, spinning in TC generated blocks, while interrupt
> +was pending unprocessed. This happened because when qemu tried to
> +handle vtimer interrupt target had interrupts disabled, as
> +result flag indicating TCG exit, cpu->icount_decr.u16.high,
> +was cleared but arm_cpu_exec_interrupt function did not call
> +arm_cpu_do_interrupt to process interrupt. Later when target
> +reenabled interrupts, it happened without exit into main loop, so
> +following code that waited for result of interrupt execution
> +run in infinite loop.
> +
> +To solve the problem instructions that operate on CPU sys state
> +(i.e enable/disable interrupt), and marked as DISAS_UPDATE,
> +should be considered as DISAS_EXIT variant, and should be
> +forced to exit back to main loop so qemu will have a chance
> +processing pending CPU state updates, including pending
> +interrupts.
> +
> +This change brings consistency with how DISAS_UPDATE is treated
> +in aarch32 case.
> +
> +CC: Peter Maydell <peter.maydell at linaro.org>
> +CC: Alex Bennée <alex.bennee at linaro.org>
> +CC: qemu-stable at nongnu.org
> +Suggested-by: Peter Maydell <peter.maydell at linaro.org>
> +Signed-off-by: Victor Kamensky <kamensky at cisco.com>
> +Reviewed-by: Richard Henderson <richard.henderson at linaro.org>
> +Message-id: 1521526368-1996-1-git-send-email-kamensky at cisco.com
> +Signed-off-by: Peter Maydell <peter.maydell at linaro.org>
> +Upstream-Status: Backport
> +---
> + target/arm/translate-a64.c | 6 +++---
> + 1 file changed, 3 insertions(+), 3 deletions(-)
> +
> +diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
> +index 31ff047..327513e 100644
> +--- a/target/arm/translate-a64.c
> ++++ b/target/arm/translate-a64.c
> +@@ -13378,12 +13378,12 @@ static void aarch64_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)
> +         case DISAS_UPDATE:
> +             gen_a64_set_pc_im(dc->pc);
> +             /* fall through */
> +-        case DISAS_JUMP:
> +-            tcg_gen_lookup_and_goto_ptr();
> +-            break;
> +         case DISAS_EXIT:
> +             tcg_gen_exit_tb(0);
> +             break;
> ++        case DISAS_JUMP:
> ++            tcg_gen_lookup_and_goto_ptr();
> ++            break;
> +         case DISAS_NORETURN:
> +         case DISAS_SWI:
> +             break;
> +--
> +2.7.4
> +
> --
> 2.7.4
>
> --
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