From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH LINUX RFC] xen: privcmd: implement IOCTL_PRIVCMD_MMAPBATCH_V2_UNCACHED Date: Wed, 18 Dec 2013 16:16:30 -0500 Message-ID: <20131218211630.GB11717@phenom.dumpdata.com> References: <1387387710.28680.88.camel@kazak.uk.xensource.com> <1387387837-9922-1-git-send-email-ian.campbell@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1387387837-9922-1-git-send-email-ian.campbell@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: stefano.stabellini@eu.citrix.com, julien.grall@linaro.org, tim@xen.org, xen-devel@lists.xen.org, David Vrabel , xen-devel@lists.xenproject.org, Boris Ostrovsky List-Id: xen-devel@lists.xenproject.org On Wed, Dec 18, 2013 at 05:30:37PM +0000, Ian Campbell wrote: > On ARM we want to use uncached foreign mappings while building the domain > because the guests start with MMU and caches disabled. > Why introduce a new ioctl? Could we piggyback on the old one and on ARM do the uncached. > Flushing the caches before launching the guest is problematic because there is > a window between flush and unmap where the processor might speculatively fill > a cache line. Using a non-cacheable mapping completely avoids this. > > Signed-off-by: Ian Campbell > Cc: Stefano.Stabellini@citrix.com> > Cc: Konrad Rzeszutek Wilk > Cc: Boris Ostrovsky > Cc: David Vrabel > Cc: xen-devel@lists.xenproject.org > --- > drivers/xen/privcmd.c | 15 ++++++++++----- > include/uapi/xen/privcmd.h | 2 ++ > 2 files changed, 12 insertions(+), 5 deletions(-) > > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c > index 569a13b..b5561d1 100644 > --- a/drivers/xen/privcmd.c > +++ b/drivers/xen/privcmd.c > @@ -253,6 +253,7 @@ struct mmap_batch_state { > domid_t domain; > unsigned long va; > struct vm_area_struct *vma; > + pgprot_t prot; > int index; > /* A tristate: > * 0 for no errors > @@ -285,8 +286,7 @@ static int mmap_batch_fn(void *data, void *state) > cur_page = pages[st->index++]; > > ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1, > - st->vma->vm_page_prot, st->domain, > - &cur_page); > + st->prot, st->domain, &cur_page); > > /* Store error code for second pass. */ > if (st->version == 1) { > @@ -367,7 +367,7 @@ static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs) > > static struct vm_operations_struct privcmd_vm_ops; > > -static long privcmd_ioctl_mmap_batch(void __user *udata, int version) > +static long privcmd_ioctl_mmap_batch(void __user *udata, int version, int cached) > { > int ret; > struct privcmd_mmapbatch_v2 m; > @@ -464,6 +464,8 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version) > > state.domain = m.dom; > state.vma = vma; > + state.prot = cached ? vma->vm_page_prot > + : pgprot_noncached(vma->vm_page_prot); > state.va = m.addr; > state.index = 0; > state.global_error = 0; > @@ -514,13 +516,16 @@ static long privcmd_ioctl(struct file *file, > break; > > case IOCTL_PRIVCMD_MMAPBATCH: > - ret = privcmd_ioctl_mmap_batch(udata, 1); > + ret = privcmd_ioctl_mmap_batch(udata, 1, 1); > break; > > case IOCTL_PRIVCMD_MMAPBATCH_V2: > - ret = privcmd_ioctl_mmap_batch(udata, 2); > + ret = privcmd_ioctl_mmap_batch(udata, 2, 1); > break; > > + case IOCTL_PRIVCMD_MMAPBATCH_V2_UNCACHED: > + ret = privcmd_ioctl_mmap_batch(udata, 2, 0); > + break; > default: > ret = -EINVAL; > break; > diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h > index a853168..be7e72b 100644 > --- a/include/uapi/xen/privcmd.h > +++ b/include/uapi/xen/privcmd.h > @@ -94,5 +94,7 @@ struct privcmd_mmapbatch_v2 { > _IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch)) > #define IOCTL_PRIVCMD_MMAPBATCH_V2 \ > _IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2)) > +#define IOCTL_PRIVCMD_MMAPBATCH_V2_UNCACHED \ > + _IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_mmapbatch_v2)) > > #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */ > -- > 1.7.10.4 >