Re: [PATCH v0 14/15] mshv: Remove mapping of mmio space during map user ioctl

Mukesh R
2026-01-24T02:12:25Z

On 1/23/26 10:34, Nuno Das Neves wrote:
> On 1/19/2026 10:42 PM, Mukesh R wrote:
>> From: Mukesh Rathor <mrathor@linux.microsoft.com>
>>
>> VFIO no longer puts the mmio pfn in vma->vm_pgoff. So, remove code
>> that is using it to map mmio space. It is broken and will cause
>> panic.
>
> What is the reason for having this as a separate commit from patch 15?
> It seems like removing this code and adding the mmio intercept
> handling could be done in one patch.

Just ease of review and porting patches from this branch to that
branch to that release to this release... I am sure someone would
have asked for this to be a separate patch :).

Thanks,
-Mukesh

>>
>> Signed-off-by: Mukesh Rathor <mrathor@linux.microsoft.com>
>> ---
>> drivers/hv/mshv_root_main.c | 20 ++++----------------
>> 1 file changed, 4 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
>> index 27313419828d..03f3aa9f5541 100644
>> --- a/drivers/hv/mshv_root_main.c
>> +++ b/drivers/hv/mshv_root_main.c
>> @@ -1258,16 +1258,8 @@ static int mshv_prepare_pinned_region(struct mshv_mem_region *region)
>> }
>>
>> /*
>> - * This maps two things: guest RAM and for pci passthru mmio space.
>> - *
>> - * mmio:
>> - * - vfio overloads vm_pgoff to store the mmio start pfn/spa.
>> - * - Two things need to happen for mapping mmio range:
>> - * 1. mapped in the uaddr so VMM can access it.
>> - * 2. mapped in the hwpt (gfn <-> mmio phys addr) so guest can access it.
>> - *
>> - * This function takes care of the second. The first one is managed by vfio,
>> - * and hence is taken care of via vfio_pci_mmap_fault().
>> + * This is called for both user ram and mmio space. The mmio space is not
>> + * mapped here, but later during intercept.
>> */
>> static long
>> mshv_map_user_memory(struct mshv_partition *partition,
>> @@ -1276,7 +1268,6 @@ mshv_map_user_memory(struct mshv_partition *partition,
>> struct mshv_mem_region *region;
>> struct vm_area_struct *vma;
>> bool is_mmio;
>> - ulong mmio_pfn;
>> long ret;
>>
>> if (mem.flags & BIT(MSHV_SET_MEM_BIT_UNMAP) ||
>> @@ -1286,7 +1277,6 @@ mshv_map_user_memory(struct mshv_partition *partition,
>> mmap_read_lock(current->mm);
>> vma = vma_lookup(current->mm, mem.userspace_addr);
>> is_mmio = vma ? !!(vma->vm_flags & (VM_IO | VM_PFNMAP)) : 0;
>> - mmio_pfn = is_mmio ? vma->vm_pgoff : 0;
>> mmap_read_unlock(current->mm);
>>
>> if (!vma)
>> @@ -1313,10 +1303,8 @@ mshv_map_user_memory(struct mshv_partition *partition,
>> HV_MAP_GPA_NO_ACCESS, NULL);
>> break;
>> case MSHV_REGION_TYPE_MMIO:
>> - ret = hv_call_map_mmio_pages(partition->pt_id,
>> - region->start_gfn,
>> - mmio_pfn,
>> - region->nr_pages);
>> + /* mmio mappings are handled later during intercepts */
>> + ret = 0;
>> break;
>> }
>>
>