Re: [PATCH v2 01/11] xen/riscv: implement get_page_from_gfn()

[Jan Beulich <jbeulich@suse.com>]

On 30.03.2026 15:40, Oleksii Kurochko wrote:
> On 3/26/26 2:50 PM, Jan Beulich wrote:
>> On 23.03.2026 17:29, Oleksii Kurochko wrote:
>>> +    if ( page->u.inuse.type_info & PGT_writable_page )
>>> +        *t = p2m_ram_rw;
>>> +    else
>>> +        BUG_ON("unimplemented. p2m_ram_ro hasn't been introduced yet");
>>> +
>>> +    return page;
>>> +}
>>
>> Finally, what doesn't become clear at all is why dom_xen needs special
>> casing. ISTR that when looking at the Arm code in the context of reviewing
>> v1, I spotted why Arm has this special case. Maybe I'm misremembering, as
>> now I can't spot it again / anymore. Yet whatever the reason there may not
>> apply at all to RISC-V.
> 
> IIUC, then Arm having this special case for DOMID_XEN as it is used to 
> share pages beloging to the hypervisor, for example, trace buffers and 
> considering that trace buffers are part of common code it will be also 
> true for RISC-V.

Ah yes, share_xen_page_with_privileged_guests() is what I didn't spot this
time round. But then you also need to implement the XENMAPSPACE_gmfn_foreign
case of xenmem_add_to_physmap_one() for this code to actually be reachable.
IOW either you make crystal clear (by way of commentary) why the case wants
dealing with, or both parts get introduced together (thus making their
connection obvious).

Jan