Re: [PATCH V2 28/45] vfio: return mr from vfio_get_xlat_addr

[Steven Sistare <steven.sistare@oracle.com>]

cc memory reviewers.
The series is here:
   https://lore.kernel.org/qemu-devel/1739542467-226739-1-git-send-email-steven.sistare@oracle.com/

- Steve

On 2/14/2025 9:14 AM, Steve Sistare wrote:
> Modify memory_get_xlat_addr and vfio_get_xlat_addr to return the memory
> region that the translated address is found in.  This will be needed by
> CPR in a subsequent patch to map blocks using IOMMU_IOAS_MAP_FILE.
> 
> Also return the xlat offset, so we can simplify the interface by removing
> the out parameters that can be trivially derived from mr and xlat.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>   hw/vfio/common.c       | 21 ++++++++++++++-------
>   hw/virtio/vhost-vdpa.c |  8 ++++++--
>   include/exec/memory.h  |  6 +++---
>   system/memory.c        | 19 ++++---------------
>   4 files changed, 27 insertions(+), 27 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index c536698..3b0c520 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -246,14 +246,13 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
>   }
>   
>   /* Called with rcu_read_lock held.  */
> -static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> -                               ram_addr_t *ram_addr, bool *read_only,
> -                               Error **errp)
> +static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, MemoryRegion **mr_p,
> +                               hwaddr *xlat_p, Error **errp)
>   {
>       bool ret, mr_has_discard_manager;
>   
> -    ret = memory_get_xlat_addr(iotlb, vaddr, ram_addr, read_only,
> -                               &mr_has_discard_manager, errp);
> +    ret = memory_get_xlat_addr(iotlb, &mr_has_discard_manager, mr_p, xlat_p,
> +                               errp);
>       if (ret && mr_has_discard_manager) {
>           /*
>            * Malicious VMs might trigger discarding of IOMMU-mapped memory. The
> @@ -281,6 +280,8 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>       VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
>       VFIOContainerBase *bcontainer = giommu->bcontainer;
>       hwaddr iova = iotlb->iova + giommu->iommu_offset;
> +    MemoryRegion *mr;
> +    hwaddr xlat;
>       void *vaddr;
>       int ret;
>       Error *local_err = NULL;
> @@ -300,10 +301,13 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>       if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
>           bool read_only;
>   
> -        if (!vfio_get_xlat_addr(iotlb, &vaddr, NULL, &read_only, &local_err)) {
> +        if (!vfio_get_xlat_addr(iotlb, &mr, &xlat, &local_err)) {
>               error_report_err(local_err);
>               goto out;
>           }
> +        vaddr = memory_region_get_ram_ptr(mr) + xlat;
> +        read_only = !(iotlb->perm & IOMMU_WO) || mr->readonly;
> +
>           /*
>            * vaddr is only valid until rcu_read_unlock(). But after
>            * vfio_dma_map has set up the mapping the pages will be
> @@ -1259,6 +1263,8 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>       ram_addr_t translated_addr;
>       Error *local_err = NULL;
>       int ret = -EINVAL;
> +    MemoryRegion *mr;
> +    ram_addr_t xlat;
>   
>       trace_vfio_iommu_map_dirty_notify(iova, iova + iotlb->addr_mask);
>   
> @@ -1269,10 +1275,11 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>       }
>   
>       rcu_read_lock();
> -    if (!vfio_get_xlat_addr(iotlb, NULL, &translated_addr, NULL, &local_err)) {
> +    if (!vfio_get_xlat_addr(iotlb, &mr, &xlat, &local_err)) {
>           error_report_err(local_err);
>           goto out_unlock;
>       }
> +    translated_addr = memory_region_get_ram_addr(mr) + xlat;
>   
>       ret = vfio_get_dirty_bitmap(bcontainer, iova, iotlb->addr_mask + 1,
>                                   translated_addr, &local_err);
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 3cdaa12..5dfe51e 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -209,6 +209,8 @@ static void vhost_vdpa_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>       int ret;
>       Int128 llend;
>       Error *local_err = NULL;
> +    MemoryRegion *mr;
> +    hwaddr xlat;
>   
>       if (iotlb->target_as != &address_space_memory) {
>           error_report("Wrong target AS \"%s\", only system memory is allowed",
> @@ -228,11 +230,13 @@ static void vhost_vdpa_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>       if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
>           bool read_only;
>   
> -        if (!memory_get_xlat_addr(iotlb, &vaddr, NULL, &read_only, NULL,
> -                                  &local_err)) {
> +        if (!memory_get_xlat_addr(iotlb, NULL, &mr, &xlat, &local_err)) {
>               error_report_err(local_err);
>               return;
>           }
> +        vaddr = memory_region_get_ram_ptr(mr) + xlat;
> +        read_only = !(iotlb->perm & IOMMU_WO) || mr->readonly;
> +
>           ret = vhost_vdpa_dma_map(s, VHOST_VDPA_GUEST_PA_ASID, iova,
>                                    iotlb->addr_mask + 1, vaddr, read_only);
>           if (ret) {
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index ea5d33a..8590838 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -747,13 +747,13 @@ void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
>    * @read_only: indicates if writes are allowed
>    * @mr_has_discard_manager: indicates memory is controlled by a
>    *                          RamDiscardManager
> + * @mr_p: return the MemoryRegion containing the @iotlb translated addr
>    * @errp: pointer to Error*, to store an error if it happens.
>    *
>    * Return: true on success, else false setting @errp with error.
>    */
> -bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> -                          ram_addr_t *ram_addr, bool *read_only,
> -                          bool *mr_has_discard_manager, Error **errp);
> +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, bool *mr_has_discard_manager,
> +                          MemoryRegion **mr_p, hwaddr *xlat_p, Error **errp);
>   
>   typedef struct CoalescedMemoryRange CoalescedMemoryRange;
>   typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
> diff --git a/system/memory.c b/system/memory.c
> index 4c82979..755eafe 100644
> --- a/system/memory.c
> +++ b/system/memory.c
> @@ -2183,9 +2183,8 @@ void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
>   }
>   
>   /* Called with rcu_read_lock held.  */
> -bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> -                          ram_addr_t *ram_addr, bool *read_only,
> -                          bool *mr_has_discard_manager, Error **errp)
> +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, bool *mr_has_discard_manager,
> +                          MemoryRegion **mr_p, hwaddr *xlat_p, Error **errp)
>   {
>       MemoryRegion *mr;
>       hwaddr xlat;
> @@ -2238,18 +2237,8 @@ bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
>           return false;
>       }
>   
> -    if (vaddr) {
> -        *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> -    }
> -
> -    if (ram_addr) {
> -        *ram_addr = memory_region_get_ram_addr(mr) + xlat;
> -    }
> -
> -    if (read_only) {
> -        *read_only = !writable || mr->readonly;
> -    }
> -
> +    *xlat_p = xlat;
> +    *mr_p = mr;
>       return true;
>   }
>