Re: [PATCH 11/22] x86: add a boot option to enable and disable the direct map

[Elias El Yandouzi <eliasely@xxxxxxxxxx>]

Hi,

On 22/12/2022 13:24, Jan Beulich wrote:
> That said, I think this change comes too early in the series, or there is
> something missing. 
At first, I had the same feeling but looking at the rest of the series, 
I can see that the option is needed in follow-up patches.
> As said in reply to patch 10, while there the mapcache
> is being initialized for the idle domain, I don't think it can be used
> just yet. Read through mapcache_current_vcpu() to understand why I think
> that way, paying particular attention to the ASSERT() near the end.
Would be able to elaborate a bit more why you think that? I haven't been 
able to get your point.
> In preparation of this patch here I think the mfn_to_virt() uses have to all
> disappear from map_domain_page(). Perhaps yet more strongly all
> ..._to_virt() (except fix_to_virt() and friends) and __va() have to
> disappear up front from x86 and any code path which can be taken on x86
> (which may simply mean purging all respective x86 #define-s, without
> breaking the build in any way).
I agree with you on that one. I think it is what we're aiming for in the 
long term. However, as mentioned by Julien in the cover letter, the 
series's name is a misnomer and I am afraid we won't be able to remove 
all of them with this series. These helpers would still be used for 
xenheap pages or when the direct map is enabled.
--
Elias