Re: [Xen-devel] [PATCH for-4.5 v11 4/9] xen/arm: Data abort exception (R/W) mem_events.

[Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

On Mon, Sep 29, 2014 at 2:35 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

Hi Tamas,

On 09/29/2014 12:36 PM, Tamas K Lengyel wrote:
> @@ -776,6 +863,8 @@ static int apply_p2m_changes(struct domain *d,
>      unsigned int cur_root_table = ~0;
>      unsigned int cur_offset[4] = { ~0, };
>      unsigned int count = 0;
> +    unsigned long sgfn = paddr_to_pfn(start_gpaddr),
> +                  egfn = paddr_to_pfn(end_gpaddr);

NIT: const unsigned long

Ack.
 

[..]

> +/* Set access type for a region of pfns.
> + * If start_pfn == -1ul, sets the default access type */
> +long p2m_set_mem_access(struct domain *d, unsigned long pfn, uint32_t nr,
> +                        uint32_t start, uint32_t mask, xenmem_access_t access)
> +{


[..]

> +
> +    rc = apply_p2m_changes(d, MEMACCESS,
> +                           pfn_to_paddr(pfn+start), pfn_to_paddr(pfn+nr),
> +                           0, MATTR_MEM, mask, 0, a);
> +
> +    flush_tlb_domain(d);
> +    iommu_iotlb_flush(d, pfn+start, nr-start);

With your solution, when rc == 0 (i.e the call memaccess has been fully
applied), you will have one more TLB flush: one in apply_p2m_changes,
the other one here...

No, I don't flush it in apply_p2m_changes, *flush is not set to true in MEMACCESS in this version.

 

As this code already exists in apply_p2m_changes but in the wrong place,
why didn't you move it later?

The problem is with the preemption case that just goes to out. I found it cleaner to just flush the tlb here for both cases instead of having the preemption case going to a flush: label then to out. If that's preferred, I'm OK with that approach too.

Tamas

 

Regards,

--
Julien Grall

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