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Re: [PATCH for-5.2 2/3] linux-user/sparc: Correct set/get_context handli
From: |
Richard Henderson |
Subject: |
Re: [PATCH for-5.2 2/3] linux-user/sparc: Correct set/get_context handling of fp and i7 |
Date: |
Thu, 5 Nov 2020 14:22:04 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 |
On 11/5/20 1:23 PM, Peter Maydell wrote:
> Because QEMU's user-mode emulation just directly accesses guest CPU
> state, for SPARC the guest register window state is not the same in
> the sparc64_get_context() and sparc64_set_context() functions as it
> is for the real kernel's versions of those functions. Specifically,
> for the kernel it has saved the user space state such that the O*
> registers go into a pt_regs struct as UREG_I*, and the I* registers
> have been spilled onto the userspace stack. For QEMU, we haven't
> done that, so the guest's O* registers are still in WREG_O* and the
> I* registers in WREG_I*.
>
> The code was already accessing the O* registers correctly for QEMU,
> but had copied the kernel code for accessing the I* registers off the
> userspace stack. Replace this with direct accesses to fp and i7 in
> the CPU state, and add a comment explaining why we differ from the
> kernel code here.
>
> This fix is sufficient to get bash to a shell prompt.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> I'm really pretty unsure about our handling of SPARC register
> windows here. This fix works, but should we instead be
> ensuring that the flush_windows() call cpu_loop() does
> before handling this trap has written the I* regs to the
> stack ???
> ---
Ach, I was so close to being right the last time I tried to clean up this code.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
- [PATCH for-5.2 0/3] linux-user: fix various sparc64 guest bugs, Peter Maydell, 2020/11/05
- [PATCH for-5.2 2/3] linux-user/sparc: Correct set/get_context handling of fp and i7, Peter Maydell, 2020/11/05
- [PATCH for-5.2 3/3] linux-user/sparc: Don't zero high half of PC, NPC, PSR in sigreturn, Peter Maydell, 2020/11/05
- Re: [PATCH for-5.2 0/3] linux-user: fix various sparc64 guest bugs, Mark Cave-Ayland, 2020/11/10