Commit a340b3e2 authored Jan 17, 2018 by KarimAllah Ahmed Committed by Radim Krčmář Jan 31, 2018

kvm: Map PFN-type memory regions as writable (if possible)



For EPT-violations that are triggered by a read, the pages are also mapped with
write permissions (if their memory region is also writable). That would avoid
getting yet another fault on the same page when a write occurs.

This optimization only happens when you have a "struct page" backing the memory
region. So also enable it for memory regions that do not have a "struct page".

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

parent e5317539

virt/kvm/kvm_main.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1428,7 +1428,8 @@ static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)

		static int hva_to_pfn_remapped(struct vm_area_struct *vma,
		unsigned long addr, bool *async,
		bool write_fault, kvm_pfn_t *p_pfn)
		bool write_fault, bool *writable,
		kvm_pfn_t *p_pfn)
		{
		unsigned long pfn;
		int r;
		@@ -1454,6 +1455,8 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,

		}

		if (writable)
		*writable = true;

		/*
		* Get a reference here because callers of hva_to_pfn and
		@@ -1519,7 +1522,7 @@ retry:
		if (vma == NULL)
		pfn = KVM_PFN_ERR_FAULT;
		else if (vma->vm_flags & (VM_IO \| VM_PFNMAP)) {
		r = hva_to_pfn_remapped(vma, addr, async, write_fault, &pfn);
		r = hva_to_pfn_remapped(vma, addr, async, write_fault, writable, &pfn);
		if (r == -EAGAIN)
		goto retry;
		if (r < 0)

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