Re: [PATCH v2 5/8] xen/riscv: introduce asm/pmap.h header

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.07.2024 10:02, Oleksii Kurochko wrote:
> On Mon, Jul 22, 2024 at 7:27 PM Julien Grall <julien@xxxxxxx> wrote:
>>>> On 22/07/2024 15:44, Oleksii Kurochko wrote:
>>>     /* Map a 4k page in a fixmap entry */
>>>     void set_fixmap(unsigned map, mfn_t mfn, unsigned int flags)
>>>     {
>>>         pte_t pte;
>>>
>>>         pte = mfn_to_xen_entry(mfn, flags);
>>>         pte.pte |= PTE_LEAF_DEFAULT;
>>>         write_pte(&xen_fixmap[pt_index(0, FIXMAP_ADDR(map))], pte);
>>
>> It would be saner to check if you are not overwriting any existing
>> mapping as otherwise you will probably need a TLB flush.
>>
>>>     }
>>>
>>>     /* Remove a mapping from a fixmap entry */
>>>     void clear_fixmap(unsigned map)
>>>     {
>>>         pte_t pte = {0};
>>>         write_pte(&xen_fixmap[pt_index(0, FIXMAP_ADDR(map))], pte);
>>
>> Don't you need a TLB flush?
>>
> Inside write_pte() there is "sfence.vma".

That's just a fence though, not a TLB flush.

Jan