Re: [PATCH v7 2/8] KVM: Introduce __kvm_follow_pfn function
From: Yu Zhang <hidden>
Date: 2023-07-05 03:10:12
Also in:
kvm, kvmarm, linux-arm-kernel, lkml
quoted hunk ↗ jump to hunk
@@ -2514,35 +2512,26 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault, * The slow path to get the pfn of the specified host virtual address, * 1 indicates success, -errno is returned if error is detected. */ -static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault, - bool interruptible, bool *writable, kvm_pfn_t *pfn) +static int hva_to_pfn_slow(struct kvm_follow_pfn *foll, kvm_pfn_t *pfn) { - unsigned int flags = FOLL_HWPOISON; + unsigned int flags = FOLL_HWPOISON | FOLL_GET | foll->flags; struct page *page; int npages; might_sleep(); - if (writable) - *writable = write_fault; - - if (write_fault) - flags |= FOLL_WRITE; - if (async) - flags |= FOLL_NOWAIT; - if (interruptible) - flags |= FOLL_INTERRUPTIBLE; - - npages = get_user_pages_unlocked(addr, 1, &page, flags); + npages = get_user_pages_unlocked(foll->hva, 1, &page, flags); if (npages != 1) return npages; + foll->writable = (foll->flags & FOLL_WRITE) && foll->allow_write_mapping; + /* map read fault as writable if possible */ - if (unlikely(!write_fault) && writable) { + if (unlikely(!foll->writable) && foll->allow_write_mapping) {
I guess !foll->writable should be !(foll->flags & FOLL_WRITE) here.
quoted hunk ↗ jump to hunk
struct page *wpage; - if (get_user_page_fast_only(addr, FOLL_WRITE, &wpage)) { - *writable = true; + if (get_user_page_fast_only(foll->hva, FOLL_WRITE, &wpage)) { + foll->writable = true; put_page(page); page = wpage; }@@ -2572,23 +2561,23 @@ static int kvm_try_get_pfn(kvm_pfn_t pfn) return get_page_unless_zero(page); }
...
+kvm_pfn_t __gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn,
+ bool atomic, bool interruptible, bool *async,
+ bool write_fault, bool *writable, hva_t *hva)
+{
+ kvm_pfn_t pfn;
+ struct kvm_follow_pfn foll = {
+ .slot = slot,
+ .gfn = gfn,
+ .flags = 0,
+ .atomic = atomic,
+ .allow_write_mapping = !!writable,
+ };
+
+ if (write_fault)
+ foll.flags |= FOLL_WRITE;
+ if (async)
+ foll.flags |= FOLL_NOWAIT;
+ if (interruptible)
+ foll.flags |= FOLL_INTERRUPTIBLE;
+
+ pfn = __kvm_follow_pfn(&foll);
+ if (pfn == KVM_PFN_ERR_NEEDS_IO) {Could we just use KVM_PFN_ERR_FAULT and foll.flags here? I.e., if (pfn == KVM_PFN_ERR_FAULT && (foll.flags & FOLL_NOWAIT))? Setting pfn to KVM_PFN_ERR_NEEDS_IO just to indicate an async fault seems unnecessary.
+ *async = true; + pfn = KVM_PFN_ERR_FAULT; + } + if (hva) + *hva = foll.hva; + if (writable) + *writable = foll.writable; + return pfn; } EXPORT_SYMBOL_GPL(__gfn_to_pfn_memslot);
B.R. Yu