On Thu, Jul 6, 2023 at 10:34 AM Isaku Yamahata [off-list ref] wrote:

On Tue, Jul 04, 2023 at 04:50:47PM +0900,
David Stevens [off-list ref] wrote:

quoted

From: David Stevens <redacted>

Introduce __kvm_follow_pfn, which will replace __gfn_to_pfn_memslot.
__kvm_follow_pfn refactors the old API's arguments into a struct and,
where possible, combines the boolean arguments into a single flags
argument.

Signed-off-by: David Stevens <redacted>
---
 include/linux/kvm_host.h |  16 ++++
 virt/kvm/kvm_main.c      | 171 ++++++++++++++++++++++-----------------
 virt/kvm/kvm_mm.h        |   3 +-
 virt/kvm/pfncache.c      |   8 +-
 4 files changed, 122 insertions(+), 76 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 9d3ac7720da9..ef2763c2b12e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h

@@ -97,6 +97,7 @@
 #define KVM_PFN_ERR_HWPOISON (KVM_PFN_ERR_MASK + 1)
 #define KVM_PFN_ERR_RO_FAULT (KVM_PFN_ERR_MASK + 2)
 #define KVM_PFN_ERR_SIGPENDING       (KVM_PFN_ERR_MASK + 3)
+#define KVM_PFN_ERR_NEEDS_IO (KVM_PFN_ERR_MASK + 4)

 /*
  * error pfns indicate that the gfn is in slot but faild to

@@ -1156,6 +1157,21 @@ unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot, gfn_t gfn,
 void kvm_release_page_clean(struct page *page);
 void kvm_release_page_dirty(struct page *page);

+struct kvm_follow_pfn {
+     const struct kvm_memory_slot *slot;
+     gfn_t gfn;
+     unsigned int flags;
+     bool atomic;
+     /* Allow a read fault to create a writeable mapping. */
+     bool allow_write_mapping;

Maybe, make them const for input arguments?

Unfortunately using const isn't straightforward as long as the kernel
continues to use -Wdeclaration-after-statement. If these fields were
const, then they would need to be specified in the initializer when
declaring the variable, but that's not necessarily always possible.

-David

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