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SubjectRe: [PATCH 3/3] xen/virtio: enable grant based virtio on x86
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On 06.10.22 18:04, Oleksandr Tyshchenko wrote:
>
> On 06.10.22 10:15, Juergen Gross wrote:
>
>
> Hello Juergen
>
>> Use an x86-specific virtio_check_mem_acc_cb() for Xen in order to setup
>> the correct DMA ops.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>> arch/x86/xen/enlighten_hvm.c | 2 +-
>> arch/x86/xen/enlighten_pv.c | 2 +-
>> drivers/xen/grant-dma-ops.c | 10 ++++++++++
>> include/xen/xen-ops.h | 1 +
>> 4 files changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
>> index 1c1ac418484b..c1cd28e915a3 100644
>> --- a/arch/x86/xen/enlighten_hvm.c
>> +++ b/arch/x86/xen/enlighten_hvm.c
>> @@ -212,7 +212,7 @@ static void __init xen_hvm_guest_init(void)
>> return;
>>
>> if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
>> - virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
>> + virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
>>
>> init_hvm_pv_info();
>>
>> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
>> index 9b1a58dda935..45b24c1b646a 100644
>> --- a/arch/x86/xen/enlighten_pv.c
>> +++ b/arch/x86/xen/enlighten_pv.c
>> @@ -112,7 +112,7 @@ static void __init xen_pv_init_platform(void)
>> {
>> /* PV guests can't operate virtio devices without grants. */
>> if (IS_ENABLED(CONFIG_XEN_VIRTIO))
>> - virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
>> + virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
>>
>> populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));
>>
>> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
>> index a00112235877..60a7acc334ed 100644
>> --- a/drivers/xen/grant-dma-ops.c
>> +++ b/drivers/xen/grant-dma-ops.c
>> @@ -372,6 +372,16 @@ void xen_grant_setup_dma_ops(struct device *dev)
>> dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
>> }
>>
>> +bool xen_virtio_restricted_mem_acc(struct virtio_device *dev)
>> +{
>> + bool ret = xen_virtio_mem_acc(dev);
>
>
> The grant usage is mandatory for PV guests, right?
>
> Then xen_virtio_mem_acc() should always return true for PV guests (I
> mean even if CONFIG_XEN_VIRTIO_FORCE_GRANT is not set).

Yes.

>
>
>
>> +
>> + if (ret)
>> + xen_grant_setup_dma_ops(dev->dev.parent);
>> +
>> + return ret;
>> +}
>> +
>> MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
>> MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
>> MODULE_LICENSE("GPL");
>> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
>> index dae0f350c678..3dd5aa936f1d 100644
>> --- a/include/xen/xen-ops.h
>> +++ b/include/xen/xen-ops.h
>> @@ -219,6 +219,7 @@ static inline void xen_preemptible_hcall_end(void) { }
>> void xen_grant_setup_dma_ops(struct device *dev);
>> bool xen_is_grant_dma_device(struct device *dev);
>> bool xen_virtio_mem_acc(struct virtio_device *dev);
>> +bool xen_virtio_restricted_mem_acc(struct virtio_device *dev);
>> #else
>> static inline void xen_grant_setup_dma_ops(struct device *dev)
>> {
>
>
> And probably static inline stub always returning false if
> CONFIG_XEN_GRANT_DMA_OPS is not set.

Indeed.


Juergen

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