On 8/20/20 6:59 PM, Sean Christopherson wrote:
On Thu, Aug 20, 2020 at 12:05:00PM -0500, Eric van Tassell wrote:
On 8/19/20 11:05 AM, Sean Christopherson wrote:
On Wed, Aug 19, 2020 at 11:03:48AM -0500, Eric van Tassell wrote:
On 8/3/20 11:27 AM, Sean Christopherson wrote:
On Sun, Aug 02, 2020 at 03:53:54PM -0500, Eric van Tassell wrote:
On 7/31/20 3:25 PM, Sean Christopherson wrote:
On Fri, Jul 24, 2020 at 06:54:46PM -0500, eric van tassell wrote:
Improve SEV guest startup time from O(n) to a constant by deferring
guest page pinning until the pages are used to satisfy nested page faults.
Implement the code to do the pinning (sev_get_page) and the notifier
sev_set_spte_notify().
Track the pinned pages with xarray so they can be released during guest
termination.
I like that SEV is trying to be a better citizen, but this is trading one
hack for another.
- KVM goes through a lot of effort to ensure page faults don't need to
allocate memory, and this throws all that effort out the window.
can you elaborate on that?
mmu_topup_memory_caches() is called from the page fault handlers before
acquiring mmu_lock to pre-allocate shadow pages, PTE list descriptors, GFN
arrays, etc... that may be needed to handle the page fault. This allows
using standard GFP flags for the allocation and obviates the need for error
handling in the consumers.
I see what you meant. The issue that causes us to use this approach is that
we need to be able to unpin the pages when the VM exits.
Yes, but using a software available flag in the SPTE to track pinned pages
should be very doable.
The issue, as I understand it, is that when spte(s) get zapped/unzapped, the
flags are lost so we'd have to have some mechanism to, before zapping, cache
the pfn <-> spte mapping
The issue is that code doesn't exist :-)
let me look into that and discuss it in our team meeting
The idea is to leave the pfn in the spte itself when a pinned spte is zapped,
and use software available bits in the spte to indicate the page is pinned
and has zap. When the VM is destroyed, remove all sptes and drop the page
reference for pinned pages.
