From: KarimAllah Ahmed <karahmed@amazon.de>
To: x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>
Cc: Filippo Sironi <sironi@amazon.de>, KarimAllah Ahmed <karahmed@amazon.de>
Subject: [PATCH v6 03/14] X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs
Date: Thu, 31 Jan 2019 21:24:33 +0100 [thread overview]
Message-ID: <1548966284-28642-4-git-send-email-karahmed@amazon.de> (raw)
In-Reply-To: <1548966284-28642-1-git-send-email-karahmed@amazon.de>
From: Filippo Sironi <sironi@amazon.de>
cmpxchg_gpte() calls get_user_pages_fast() to retrieve the number of
pages and the respective struct page to map in the kernel virtual
address space.
This doesn't work if get_user_pages_fast() is invoked with a userspace
virtual address that's backed by PFNs outside of kernel reach (e.g., when
limiting the kernel memory with mem= in the command line and using
/dev/mem to map memory).
If get_user_pages_fast() fails, look up the VMA that back the userspace
virtual address, compute the PFN and the physical address, and map it in
the kernel virtual address space with memremap().
Signed-off-by: Filippo Sironi <sironi@amazon.de>
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
---
arch/x86/kvm/paging_tmpl.h | 38 +++++++++++++++++++++++++++++---------
1 file changed, 29 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 6bdca39..c40af67 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -141,15 +141,35 @@ static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
struct page *page;
npages = get_user_pages_fast((unsigned long)ptep_user, 1, 1, &page);
- /* Check if the user is doing something meaningless. */
- if (unlikely(npages != 1))
- return -EFAULT;
-
- table = kmap_atomic(page);
- ret = CMPXCHG(&table[index], orig_pte, new_pte);
- kunmap_atomic(table);
-
- kvm_release_page_dirty(page);
+ if (likely(npages == 1)) {
+ table = kmap_atomic(page);
+ ret = CMPXCHG(&table[index], orig_pte, new_pte);
+ kunmap_atomic(table);
+
+ kvm_release_page_dirty(page);
+ } else {
+ struct vm_area_struct *vma;
+ unsigned long vaddr = (unsigned long)ptep_user & PAGE_MASK;
+ unsigned long pfn;
+ unsigned long paddr;
+
+ down_read(¤t->mm->mmap_sem);
+ vma = find_vma_intersection(current->mm, vaddr, vaddr + PAGE_SIZE);
+ if (!vma || !(vma->vm_flags & VM_PFNMAP)) {
+ up_read(¤t->mm->mmap_sem);
+ return -EFAULT;
+ }
+ pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+ paddr = pfn << PAGE_SHIFT;
+ table = memremap(paddr, PAGE_SIZE, MEMREMAP_WB);
+ if (!table) {
+ up_read(¤t->mm->mmap_sem);
+ return -EFAULT;
+ }
+ ret = CMPXCHG(&table[index], orig_pte, new_pte);
+ memunmap(table);
+ up_read(¤t->mm->mmap_sem);
+ }
return (ret != orig_pte);
}
--
2.7.4
next prev parent reply other threads:[~2019-01-31 20:24 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-31 20:24 [PATCH v6 00/14] KVM/X86: Introduce a new guest mapping interface KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 01/14] X86/nVMX: handle_vmon: Read 4 bytes from guest memory KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 02/14] X86/nVMX: Update the PML table without mapping and unmapping the page KarimAllah Ahmed
2019-01-31 20:24 ` KarimAllah Ahmed [this message]
2019-01-31 20:24 ` [PATCH v6 04/14] KVM: Introduce a new guest mapping API KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 05/14] X86/nVMX: handle_vmptrld: Use kvm_vcpu_map when copying VMCS12 from guest memory KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 06/14] KVM/nVMX: Use kvm_vcpu_map when mapping the L1 MSR bitmap KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 07/14] KVM/nVMX: Use kvm_vcpu_map when mapping the virtual APIC page KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 08/14] KVM/nVMX: Use kvm_vcpu_map when mapping the posted interrupt descriptor table KarimAllah Ahmed
2021-05-06 23:06 ` Jim Mattson
2021-05-06 23:27 ` Sean Christopherson
2019-01-31 20:24 ` [PATCH v6 09/14] KVM/X86: Use kvm_vcpu_map in emulator_cmpxchg_emulated KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 10/14] KVM/nSVM: Use the new mapping API for mapping guest memory KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 11/14] KVM/nVMX: Use kvm_vcpu_map for accessing the shadow VMCS KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 12/14] KVM/nVMX: Use kvm_vcpu_map for accessing the enlightened VMCS KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 13/14] KVM/nVMX: Use page_address_valid in a few more locations KarimAllah Ahmed
2019-01-31 20:24 ` [PATCH v6 14/14] kvm, x86: Properly check whether a pfn is an MMIO or not KarimAllah Ahmed
2019-03-18 13:10 ` [PATCH v6 00/14] KVM/X86: Introduce a new guest mapping interface Raslan, KarimAllah
2019-03-18 14:22 ` Konrad Rzeszutek Wilk
2019-03-18 19:16 ` Raslan, KarimAllah
2019-04-29 13:58 ` Konrad Rzeszutek Wilk
2019-04-30 19:31 ` Paolo Bonzini
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