Le 24/07/2020 à 05:03, Bharata B Rao a écrit :
On Thu, Jul 23, 2020 at 01:07:24PM -0700, Ram Pai wrote:From: Laurent Dufour <ldufour@xxxxxxxxxxxxx> When a secure memslot is dropped, all the pages backed in the secure device (aka really backed by secure memory by the Ultravisor) should be paged out to a normal page. Previously, this was achieved by triggering the page fault mechanism which is calling kvmppc_svm_page_out() on each pages. This can't work when hot unplugging a memory slot because the memory slot is flagged as invalid and gfn_to_pfn() is then not trying to access the page, so the page fault mechanism is not triggered. Since the final goal is to make a call to kvmppc_svm_page_out() it seems simpler to call directly instead of triggering such a mechanism. This way kvmppc_uvmem_drop_pages() can be called even when hot unplugging a memslot. Since kvmppc_uvmem_drop_pages() is already holding kvm->arch.uvmem_lock, the call to __kvmppc_svm_page_out() is made. As __kvmppc_svm_page_out needs the vma pointer to migrate the pages, the VMA is fetched in a lazy way, to not trigger find_vma() all the time. In addition, the mmap_sem is held in read mode during that time, not in write mode since the virual memory layout is not impacted, and kvm->arch.uvmem_lock prevents concurrent operation on the secure device. Cc: Ram Pai <linuxram@xxxxxxxxxx> Cc: Bharata B Rao <bharata@xxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxxx> Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx> [modified the changelog description] Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx> --- arch/powerpc/kvm/book3s_hv_uvmem.c | 54 ++++++++++++++++++++++++++------------ 1 file changed, 37 insertions(+), 17 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c index c772e92..daffa6e 100644 --- a/arch/powerpc/kvm/book3s_hv_uvmem.c +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c @@ -632,35 +632,55 @@ static inline int kvmppc_svm_page_out(struct vm_area_struct *vma, * fault on them, do fault time migration to replace the device PTEs in * QEMU page table with normal PTEs from newly allocated pages. */ -void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *free, +void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *slot, struct kvm *kvm, bool skip_page_out) { int i; struct kvmppc_uvmem_page_pvt *pvt; - unsigned long pfn, uvmem_pfn; - unsigned long gfn = free->base_gfn; + struct page *uvmem_page; + struct vm_area_struct *vma = NULL; + unsigned long uvmem_pfn, gfn; + unsigned long addr, end; + + mmap_read_lock(kvm->mm); + + addr = slot->userspace_addr; + end = addr + (slot->npages * PAGE_SIZE);- for (i = free->npages; i; --i, ++gfn) {- struct page *uvmem_page; + gfn = slot->base_gfn; + for (i = slot->npages; i; --i, ++gfn, addr += PAGE_SIZE) { + + /* Fetch the VMA if addr is not in the latest fetched one */ + if (!vma || (addr < vma->vm_start || addr >= vma->vm_end)) { + vma = find_vma_intersection(kvm->mm, addr, end); + if (!vma || + vma->vm_start > addr || vma->vm_end < end) { + pr_err("Can't find VMA for gfn:0x%lx\n", gfn); + break; + }There is a potential issue with the boundary condition check here which I discussed with Laurent yesterday. Guess he hasn't gotten around to look at it yet.
Right, I'm working on that..
