[PATCH 2/2] KVM: SVM: convert get_user_pages() --> pin_user_pages()

John Hubbard
2020-05-26T06:22:12Z

This code was using get_user_pages*(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages*() + put_page() calls to
pin_user_pages*() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
https://lwn.net/Articles/807108/

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
arch/x86/kvm/svm/sev.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 9693db1af57c..a83f2e73bcbb 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -349,7 +349,7 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
return NULL;

/* Pin the user virtual address. */
- npinned = get_user_pages_fast(uaddr, npages, write ? FOLL_WRITE : 0, pages);
+ npinned = pin_user_pages_fast(uaddr, npages, write ? FOLL_WRITE : 0, pages);
if (npinned != npages) {
pr_err("SEV: Failure locking %lu pages.\n", npages);
goto err;
@@ -362,7 +362,7 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,

err:
if (npinned > 0)
- release_pages(pages, npinned);
+ unpin_user_pages(pages, npinned);

kvfree(pages);
return NULL;
@@ -373,7 +373,7 @@ static void sev_unpin_memory(struct kvm *kvm, struct page **pages,
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;

- release_pages(pages, npages);
+ unpin_user_pages(pages, npages);
kvfree(pages);
sev->pages_locked -= npages;
}
--
2.26.2