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Re: [Qemu-devel] [Qemu-arm] [PATCH] arm: check regime, not current state

From: Alex Bennée
Subject: Re: [Qemu-devel] [Qemu-arm] [PATCH] arm: check regime, not current state, for ATS write PAR format
Date: Mon, 06 Nov 2017 16:10:10 +0000
User-agent: mu4e 1.0-alpha0; emacs 26.0.90

Peter Maydell <address@hidden> writes:

> In do_ats_write(), rather than using extended_addresses_enabled() to
> decide whether the value we get back from get_phys_addr() is a 64-bit
> format PAR or a 32-bit one, use arm_s1_regime_using_lpae_format().
> This is not really the correct answer, because the PAR format
> depends on the AT instruction being used, not just on the
> translation regime. However getting this correct requires a
> significant refactoring, so that get_phys_addr() returns raw
> information about the fault which the caller can then assemble
> into a suitable FSR/PAR/syndrome for its purposes, rather than
> get_phys_addr() returning a pre-formatted FSR.
> However this change at least improves the situation by making
> the PAR work correctly for address translation operations done
> at AArch64 EL2 on the EL2 translation regime. In particular,
> this is necessary for Xen to be able to run in our emulation,
> so this seems like a safer interim fix given that we are in freeze.
> Signed-off-by: Peter Maydell <address@hidden>

As far as it goes it seems reasonable:

Reviewed-by: Alex Bennée <address@hidden>

> ---
> I guess I should have a go at the "correct answer" I sketch
> above, but no promises about when I'll get time for that :-(
>  target/arm/helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 96113fe..37af750 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -2162,7 +2162,7 @@ static uint64_t do_ats_write(CPUARMState *env, uint64_t 
> value,
>      ret = get_phys_addr(env, value, access_type, mmu_idx,
>                          &phys_addr, &attrs, &prot, &page_size, &fsr, &fi);
> -    if (extended_addresses_enabled(env)) {
> +    if (arm_s1_regime_using_lpae_format(env, mmu_idx)) {
>          /* fsr is a DFSR/IFSR value for the long descriptor
>           * translation table format, but with WnR always clear.
>           * Convert it to a 64-bit PAR.

Alex Bennée

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