From mboxrd@z Thu Jan 1 00:00:00 1970 From: KarimAllah Ahmed Subject: [PATCH v2] kvm: Map PFN-type memory regions as writable (if possible) Date: Wed, 17 Jan 2018 19:18:56 +0100 Message-ID: <1516213136-12883-1-git-send-email-karahmed@amazon.de> References: <64411cad-77ee-2f6e-d431-78e853cae65d@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: KarimAllah Ahmed , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , linux-kernel@vger.kernel.org To: kvm@vger.kernel.org Return-path: In-Reply-To: <64411cad-77ee-2f6e-d431-78e853cae65d@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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 Cc: Radim Krčmář Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: KarimAllah Ahmed --- v2: - Move setting writable to hva_to_pfn_remapped - Extend hva_to_pfn_remapped interface to accept writable as a parameter --- virt/kvm/kvm_main.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 97da45e..88702d5 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1438,7 +1438,8 @@ 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; @@ -1464,6 +1465,8 @@ 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 @@ -1529,7 +1532,7 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async, 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) -- 2.7.4