[PATCH v13 78/85] KVM: PPC: Explicitly require struct page memory for Ultravisor sharing

Sean Christopherson
2024-10-10T18:27:38Z

Explicitly require "struct page" memory when sharing memory between
guest and host via an Ultravisor. Given the number of pfn_to_page()
calls in the code, it's safe to assume that KVM already requires that the
pfn returned by gfn_to_pfn() is backed by struct page, i.e. this is
likely a bug fix, not a reduction in KVM capabilities.

Switching to gfn_to_page() will eventually allow removing gfn_to_pfn()
and kvm_pfn_to_refcounted_page().

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/powerpc/kvm/book3s_hv_uvmem.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 92f33115144b..3a6592a31a10 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -879,9 +879,8 @@ static unsigned long kvmppc_share_page(struct kvm *kvm, unsigned long gpa,
{

int ret = H_PARAMETER;
- struct page *uvmem_page;
+ struct page *page, *uvmem_page;
struct kvmppc_uvmem_page_pvt *pvt;
- unsigned long pfn;
unsigned long gfn = gpa >> page_shift;
int srcu_idx;
unsigned long uvmem_pfn;
@@ -901,8 +900,8 @@ static unsigned long kvmppc_share_page(struct kvm *kvm, unsigned long gpa,

retry:
mutex_unlock(&kvm->arch.uvmem_lock);
- pfn = gfn_to_pfn(kvm, gfn);
- if (is_error_noslot_pfn(pfn))
+ page = gfn_to_page(kvm, gfn);
+ if (!page)
goto out;

mutex_lock(&kvm->arch.uvmem_lock);
@@ -911,16 +910,16 @@ static unsigned long kvmppc_share_page(struct kvm *kvm, unsigned long gpa,
pvt = uvmem_page->zone_device_data;
pvt->skip_page_out = true;
pvt->remove_gfn = false; /* it continues to be a valid GFN */
- kvm_release_pfn_clean(pfn);
+ kvm_release_page_unused(page);
goto retry;
}

- if (!uv_page_in(kvm->arch.lpid, pfn << page_shift, gpa, 0,
+ if (!uv_page_in(kvm->arch.lpid, page_to_pfn(page) << page_shift, gpa, 0,
page_shift)) {
kvmppc_gfn_shared(gfn, kvm);
ret = H_SUCCESS;
}
- kvm_release_pfn_clean(pfn);
+ kvm_release_page_clean(page);
mutex_unlock(&kvm->arch.uvmem_lock);
out:
srcu_read_unlock(&kvm->srcu, srcu_idx);
@@ -1083,21 +1082,21 @@ kvmppc_h_svm_page_out(struct kvm *kvm, unsigned long gpa,

int kvmppc_send_page_to_uv(struct kvm *kvm, unsigned long gfn)
{
- unsigned long pfn;
+ struct page *page;
int ret = U_SUCCESS;

- pfn = gfn_to_pfn(kvm, gfn);
- if (is_error_noslot_pfn(pfn))
+ page = gfn_to_page(kvm, gfn);
+ if (!page)
return -EFAULT;

mutex_lock(&kvm->arch.uvmem_lock);
if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL))
goto out;

- ret = uv_page_in(kvm->arch.lpid, pfn << PAGE_SHIFT, gfn << PAGE_SHIFT,
- 0, PAGE_SHIFT);
+ ret = uv_page_in(kvm->arch.lpid, page_to_pfn(page) << PAGE_SHIFT,
+ gfn << PAGE_SHIFT, 0, PAGE_SHIFT);
out:
- kvm_release_pfn_clean(pfn);
+ kvm_release_page_clean(page);
mutex_unlock(&kvm->arch.uvmem_lock);
return (ret == U_SUCCESS) ? RESUME_GUEST : -EFAULT;
}
--
2.47.0.rc1.288.g06298d1525-goog