[PATCH v13 14/85] KVM: Return ERR_SIGPENDING from hva_to_pfn() if GUP returns -EGAIN

Sean Christopherson
2024-10-10T19:46:32Z

Treat an -EAGAIN return from GUP the same as -EINTR and immediately report
to the caller that a signal is pending. GUP only returns -EAGAIN if
the _initial_ mmap_read_lock_killable() fails, which in turn onnly fails
if a signal is pending

Note, rwsem_down_read_slowpath() actually returns -EINTR, so GUP is really
just making life harder than it needs to be. And the call to
mmap_read_lock_killable() in the retry path returns its -errno verbatim,
i.e. GUP (and thus KVM) is already handling locking failure this way, but
only some of the time.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
virt/kvm/kvm_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 17acc75990a5..ebba5d22db2d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2946,7 +2946,7 @@ kvm_pfn_t hva_to_pfn(unsigned long addr, bool interruptible, bool *async,
writable, &pfn);
if (npages == 1)
return pfn;
- if (npages == -EINTR)
+ if (npages == -EINTR || npages == -EAGAIN)
return KVM_PFN_ERR_SIGPENDING;

mmap_read_lock(current->mm);