On Thu, Jul 18, 2024 at 10:03:01AM -0400, Peter Xu wrote:
On Thu, Jul 18, 2024 at 09:50:31AM +0800, Yan Zhao wrote:Hmm, by referring to pfn set 1 and pfn set 2, I mean that they're both
Ok. Then if we have two sets of pfns, then we can
1. Call remap_pfn_range() in mmap() for pfn set 1.
I don't think this will work.. At least from the current implementation,
remap_pfn_range() will only reserve the memtype if the range covers the
whole vma.
covering the entire vma, but at different times.
To make it more accurately:
Consider this hypothetical scenario (not the same as what's implemented in
vfio-pci, but seems plausible):
Suppose we have a vma covering only one page, then
(1) Initially, the vma is mapped to pfn1, with remap_pfn_range().
(2) Subsequently, unmap_single_vma() is invoked to unmap the entire VMA.
(3) The driver then maps the entire vma to pfn2 in fault handler
Given this context, my questions are:
1. How can we reserve the memory type for pfn2? Should we call
track_pfn_remap() in mmap() in advance?
2. How do we untrack the memory type for pfn1 and pfn2, considering they
belong to the same VMA but mutual exclusively and not concurrently?