From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] kvm: Map PFN-type memory regions as writable (if possible) Date: Wed, 17 Jan 2018 18:56:40 +0100 Message-ID: <64411cad-77ee-2f6e-d431-78e853cae65d@redhat.com> References: <1516209965-18614-1-git-send-email-karahmed@amazon.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org To: KarimAllah Ahmed , kvm@vger.kernel.org Return-path: In-Reply-To: <1516209965-18614-1-git-send-email-karahmed@amazon.de> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 17/01/2018 18:26, KarimAllah Ahmed wrote: > 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 > --- > virt/kvm/kvm_main.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 97da45e..0efb089 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1534,6 +1534,8 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async, > goto retry; > if (r < 0) > pfn = KVM_PFN_ERR_FAULT; > + if (writable) > + *writable = true; > } else { > if (async && vma_is_valid(vma, write_fault)) > *async = true; > Looks good, but it should be in hva_to_pfn_remapped. Paolo