[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH 1/2] target/ppc: Fixed call to deferred exception

From: Cédric Le Goater
Subject: Re: [PATCH 1/2] target/ppc: Fixed call to deferred exception
Date: Tue, 16 Nov 2021 15:43:25 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0

On 11/10/21 18:29, Lucas Mateus Martins Araujo e Castro wrote:

On 10/11/2021 03:56, Cédric Le Goater wrote:
On 11/9/21 17:37, Daniel Henrique Barboza wrote:

On 10/20/21 09:57, Lucas Mateus Castro (alqotel) wrote:
From: "Lucas Mateus Castro (alqotel)" <lucas.castro@eldorado.org.br>

mtfsf, mtfsfi and mtfsb1 instructions call helper_float_check_status
after updating the value of FPSCR, but helper_float_check_status
checks fp_status and fp_status isn't updated based on FPSCR and
since the value of fp_status is reset earlier in the instruction,
it's always 0.

Because of this helper_float_check_status would change the FI bit to 0
as this bit checks if the last operation was inexact and
float_flag_inexact is always 0.

These instructions also don't throw exceptions correctly since
helper_float_check_status throw exceptions based on fp_status.

This commit created a new helper, helper_fpscr_check_status that checks
FPSCR value instead of fp_status and checks for a larger variety of
exceptions than do_float_check_status.

The hardware used to compare QEMU's behavior to, was a Power9.

Do you have a test case for this ? If so, are you collecting them
on some repo ?



Just created a test, currently on the branch 
https://github.com/PPC64/qemu/tree/alqotel_bug_mtfsf commit 

This test if FI is being set correctly and if the deferred exception is being 
called correctly (by enabling VE and VXSOFT bits)

Nice ! May be include in the v2 ?



reply via email to

[Prev in Thread] Current Thread [Next in Thread]