linux-kernel - Re: [PATCH] selftests: kvm: Fix a potential elf loading issue

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Date:   Mon, 24 May 2021 14:27:54 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Zhenzhong Duan <zhenzhong.duan@...el.com>,
        linux-kernel@...r.kernel.org
Cc:     linux-kselftest@...r.kernel.org, kvm@...r.kernel.org,
        shuah@...nel.org
Subject: Re: [PATCH] selftests: kvm: Fix a potential elf loading issue

On 12/05/21 06:31, Zhenzhong Duan wrote:
> vm_vaddr_alloc() setup GVA to GPA mapping page by page, then GPA may not be
> continuous if same memslot is used for data and page table allocation.
> 
> kvm_vm_elf_load() expects a continuous memory of GPA or else it need to
> read file data page by page. Fix it by adding a check in vm_vaddr_alloc()
> to ensure memory is allocated in a whole if same memslot is used for data
> and page table.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...el.com>
> ---
Why not do

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 7426163d448a..f362a066f37a 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1170,6 +1170,9 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
  	uint64_t pages = (sz >> vm->page_shift) + ((sz % vm->page_size) != 0);
  
  	virt_pgd_alloc(vm, pgd_memslot);
+	vm_paddr_t paddr = vm_phy_pages_alloc(vm, pages,
+					      KVM_UTIL_MIN_PFN * vm->page_size,
+					      data_memslot);
  
  	/*
  	 * Find an unused range of virtual page addresses of at least
@@ -1179,11 +1182,7 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
  
  	/* Map the virtual pages. */
  	for (vm_vaddr_t vaddr = vaddr_start; pages > 0;
-		pages--, vaddr += vm->page_size) {
-		vm_paddr_t paddr;
-
-		paddr = vm_phy_page_alloc(vm,
-				KVM_UTIL_MIN_PFN * vm->page_size, data_memslot);
+		pages--, vaddr += vm->page_size, paddr += vm->page_size) {
  
  		virt_pg_map(vm, vaddr, paddr, pgd_memslot);
  

instead?

Paolo