Re: [PATCH 2/2] xen/privcmd: add PRIVCMD_MMAPBATCH_V2 ioctl

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Sep 05, 2012 at 01:09:32PM -0400, Andres Lagar-Cavilla wrote:
> Super. To which branch are you applying these now? (n00b question but have to ask)

They will show up on stable/for-linus-3.7 once the overnight tests pass.

> Andres
> On Sep 5, 2012, at 12:21 PM, Konrad Rzeszutek Wilk wrote:
> 
> > On Fri, Aug 31, 2012 at 09:59:30AM -0400, Andres Lagar-Cavilla wrote:
> >> Re-spin of alternative patch after David's feedback.
> >> Thanks
> >> Andres
> > 
> > applied. fixed some whitespace issues.
> >> 
> >> commit ab351a5cef1797935b083c2f6e72800a8949c515
> >> Author: Andres Lagar-Cavilla <andres@lagarcavilla.org>
> >> Date:   Thu Aug 30 12:23:33 2012 -0400
> >> 
> >>    xen/privcmd: add PRIVCMD_MMAPBATCH_V2 ioctl
> >> 
> >>    PRIVCMD_MMAPBATCH_V2 extends PRIVCMD_MMAPBATCH with an additional
> >>    field for reporting the error code for every frame that could not be
> >>    mapped.  libxc prefers PRIVCMD_MMAPBATCH_V2 over PRIVCMD_MMAPBATCH.
> >> 
> >>    Also expand PRIVCMD_MMAPBATCH to return appropriate error-encoding top nibble
> >>    in the mfn array.
> >> 
> >>    Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> >>    Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
> >> 
> >> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> >> index 85226cb..5386f20 100644
> >> --- a/drivers/xen/privcmd.c
> >> +++ b/drivers/xen/privcmd.c
> >> @@ -76,7 +76,7 @@ static void free_page_list(struct list_head *pages)
> >>  */
> >> static int gather_array(struct list_head *pagelist,
> >> 			unsigned nelem, size_t size,
> >> -			void __user *data)
> >> +			const void __user *data)
> >> {
> >> 	unsigned pageidx;
> >> 	void *pagedata;
> >> @@ -246,61 +246,117 @@ struct mmap_batch_state {
> >> 	domid_t domain;
> >> 	unsigned long va;
> >> 	struct vm_area_struct *vma;
> >> -	int err;
> >> -
> >> -	xen_pfn_t __user *user;
> >> +	/* A tristate: 
> >> +	 *      0 for no errors
> >> +	 *      1 if at least one error has happened (and no
> >> +	 *          -ENOENT errors have happened)
> >> +	 *      -ENOENT if at least 1 -ENOENT has happened.
> >> +	 */
> >> +	int global_error;
> >> +	/* An array for individual errors */
> >> +	int *err;
> >> +
> >> +	/* User-space mfn array to store errors in the second pass for V1. */
> >> +	xen_pfn_t __user *user_mfn;
> >> };
> >> 
> >> static int mmap_batch_fn(void *data, void *state)
> >> {
> >> 	xen_pfn_t *mfnp = data;
> >> 	struct mmap_batch_state *st = state;
> >> +	int ret;
> >> 
> >> -	if (xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
> >> -				       st->vma->vm_page_prot, st->domain) < 0) {
> >> -		*mfnp |= 0xf0000000U;
> >> -		st->err++;
> >> +	ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
> >> +					 st->vma->vm_page_prot, st->domain);
> >> +
> >> +	/* Store error code for second pass. */
> >> +	*(st->err++) = ret;
> >> +
> >> +	/* And see if it affects the global_error. */
> >> +	if (ret < 0) {
> >> +		if (ret == -ENOENT)
> >> +			st->global_error = -ENOENT;
> >> +		else {
> >> +			/* Record that at least one error has happened. */
> >> +			if (st->global_error == 0)
> >> +				st->global_error = 1;
> >> +		}
> >> 	}
> >> 	st->va += PAGE_SIZE;
> >> 
> >> 	return 0;
> >> }
> >> 
> >> -static int mmap_return_errors(void *data, void *state)
> >> +static int mmap_return_errors_v1(void *data, void *state)
> >> {
> >> 	xen_pfn_t *mfnp = data;
> >> 	struct mmap_batch_state *st = state;
> >> -
> >> -	return put_user(*mfnp, st->user++);
> >> +	int err = *(st->err++);
> >> +
> >> +	/*
> >> +	 * V1 encodes the error codes in the 32bit top nibble of the 
> >> +	 * mfn (with its known limitations vis-a-vis 64 bit callers).
> >> +	 */
> >> +	*mfnp |= (err == -ENOENT) ?
> >> +				PRIVCMD_MMAPBATCH_PAGED_ERROR :
> >> +				PRIVCMD_MMAPBATCH_MFN_ERROR;
> >> +	return __put_user(*mfnp, st->user_mfn++);
> >> }
> >> 
> >> static struct vm_operations_struct privcmd_vm_ops;
> >> 
> >> -static long privcmd_ioctl_mmap_batch(void __user *udata)
> >> +static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
> >> {
> >> 	int ret;
> >> -	struct privcmd_mmapbatch m;
> >> +	struct privcmd_mmapbatch_v2 m;
> >> 	struct mm_struct *mm = current->mm;
> >> 	struct vm_area_struct *vma;
> >> 	unsigned long nr_pages;
> >> 	LIST_HEAD(pagelist);
> >> +	int *err_array = NULL;
> >> 	struct mmap_batch_state state;
> >> 
> >> 	if (!xen_initial_domain())
> >> 		return -EPERM;
> >> 
> >> -	if (copy_from_user(&m, udata, sizeof(m)))
> >> -		return -EFAULT;
> >> +	switch (version) {
> >> +	case 1:
> >> +		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
> >> +			return -EFAULT;
> >> +		/* Returns per-frame error in m.arr. */
> >> +		m.err = NULL;
> >> +		if (!access_ok(VERIFY_WRITE, m.arr, m.num * sizeof(*m.arr)))
> >> +			return -EFAULT;
> >> +		break;
> >> +	case 2:
> >> +		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
> >> +			return -EFAULT;
> >> +		/* Returns per-frame error code in m.err. */
> >> +		if (!access_ok(VERIFY_WRITE, m.err, m.num * (sizeof(*m.err))))
> >> +			return -EFAULT;
> >> +		break;
> >> +	default:
> >> +		return -EINVAL;
> >> +	}
> >> 
> >> 	nr_pages = m.num;
> >> 	if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
> >> 		return -EINVAL;
> >> 
> >> -	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t),
> >> -			   m.arr);
> >> +	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);
> >> +
> >> +	if (ret)
> >> +		goto out;
> >> +	if (list_empty(&pagelist)) {
> >> +		ret = -EINVAL;
> >> +		goto out;
> >> +    }
> >> 
> >> -	if (ret || list_empty(&pagelist))
> >> +	err_array = kcalloc(m.num, sizeof(int), GFP_KERNEL);
> >> +	if (err_array == NULL) {
> >> +		ret = -ENOMEM;
> >> 		goto out;
> >> +	}
> >> 
> >> 	down_write(&mm->mmap_sem);
> >> 
> >> @@ -315,24 +371,34 @@ static long privcmd_ioctl_mmap_batch(void __user *udata)
> >> 		goto out;
> >> 	}
> >> 
> >> -	state.domain = m.dom;
> >> -	state.vma = vma;
> >> -	state.va = m.addr;
> >> -	state.err = 0;
> >> +	state.domain        = m.dom;
> >> +	state.vma           = vma;
> >> +	state.va            = m.addr;
> >> +	state.global_error  = 0;
> >> +	state.err           = err_array;
> >> 
> >> -	ret = traverse_pages(m.num, sizeof(xen_pfn_t),
> >> -			     &pagelist, mmap_batch_fn, &state);
> >> +	/* mmap_batch_fn guarantees ret == 0 */
> >> +	BUG_ON(traverse_pages(m.num, sizeof(xen_pfn_t),
> >> +			     &pagelist, mmap_batch_fn, &state));
> >> 
> >> 	up_write(&mm->mmap_sem);
> >> 
> >> -	if (state.err > 0) {
> >> -		state.user = m.arr;
> >> +	if (state.global_error && (version == 1)) {
> >> +		/* Write back errors in second pass. */
> >> +		state.user_mfn = (xen_pfn_t *)m.arr;
> >> +		state.err      = err_array;
> >> 		ret = traverse_pages(m.num, sizeof(xen_pfn_t),
> >> -			       &pagelist,
> >> -			       mmap_return_errors, &state);
> >> -	}
> >> +					 &pagelist, mmap_return_errors_v1, &state);
> >> +	} else
> >> +		ret = __copy_to_user(m.err, err_array, m.num * sizeof(int));
> >> +
> >> +    /* If we have not had any EFAULT-like global errors then set the global
> >> +     * error to -ENOENT if necessary. */
> >> +    if ((ret == 0) && (state.global_error == -ENOENT))
> >> +        ret = -ENOENT;
> >> 
> >> out:
> >> +	kfree(err_array);
> >> 	free_page_list(&pagelist);
> >> 
> >> 	return ret;
> >> @@ -354,7 +420,11 @@ static long privcmd_ioctl(struct file *file,
> >> 		break;
> >> 
> >> 	case IOCTL_PRIVCMD_MMAPBATCH:
> >> -		ret = privcmd_ioctl_mmap_batch(udata);
> >> +		ret = privcmd_ioctl_mmap_batch(udata, 1);
> >> +		break;
> >> +
> >> +	case IOCTL_PRIVCMD_MMAPBATCH_V2:
> >> +		ret = privcmd_ioctl_mmap_batch(udata, 2);
> >> 		break;
> >> 
> >> 	default:
> >> diff --git a/include/xen/privcmd.h b/include/xen/privcmd.h
> >> index 45c1aa1..a853168 100644
> >> --- a/include/xen/privcmd.h
> >> +++ b/include/xen/privcmd.h
> >> @@ -58,13 +58,33 @@ struct privcmd_mmapbatch {
> >> 	int num;     /* number of pages to populate */
> >> 	domid_t dom; /* target domain */
> >> 	__u64 addr;  /* virtual address */
> >> -	xen_pfn_t __user *arr; /* array of mfns - top nibble set on err */
> >> +	xen_pfn_t __user *arr; /* array of mfns - or'd with
> >> +				  PRIVCMD_MMAPBATCH_*_ERROR on err */
> >> +};
> >> +
> >> +#define PRIVCMD_MMAPBATCH_MFN_ERROR     0xf0000000U
> >> +#define PRIVCMD_MMAPBATCH_PAGED_ERROR   0x80000000U
> >> +
> >> +struct privcmd_mmapbatch_v2 {
> >> +	unsigned int num; /* number of pages to populate */
> >> +	domid_t dom;      /* target domain */
> >> +	__u64 addr;       /* virtual address */
> >> +	const xen_pfn_t __user *arr; /* array of mfns */
> >> +	int __user *err;  /* array of error codes */
> >> };
> >> 
> >> /*
> >>  * @cmd: IOCTL_PRIVCMD_HYPERCALL
> >>  * @arg: &privcmd_hypercall_t
> >>  * Return: Value returned from execution of the specified hypercall.
> >> + *
> >> + * @cmd: IOCTL_PRIVCMD_MMAPBATCH_V2
> >> + * @arg: &struct privcmd_mmapbatch_v2
> >> + * Return: 0 on success (i.e., arg->err contains valid error codes for
> >> + * each frame).  On an error other than a failed frame remap, -1 is
> >> + * returned and errno is set to EINVAL, EFAULT etc.  As an exception,
> >> + * if the operation was otherwise successful but any frame failed with
> >> + * -ENOENT, then -1 is returned and errno is set to ENOENT.
> >>  */
> >> #define IOCTL_PRIVCMD_HYPERCALL					\
> >> 	_IOC(_IOC_NONE, 'P', 0, sizeof(struct privcmd_hypercall))
> >> @@ -72,5 +92,7 @@ struct privcmd_mmapbatch {
> >> 	_IOC(_IOC_NONE, 'P', 2, sizeof(struct privcmd_mmap))
> >> #define IOCTL_PRIVCMD_MMAPBATCH					\
> >> 	_IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch))
> >> +#define IOCTL_PRIVCMD_MMAPBATCH_V2				\
> >> +	_IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
> >> 
> >> #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
> >> 
> >> On Aug 30, 2012, at 8:58 AM, David Vrabel wrote:
> >> 
> >>> From: David Vrabel <david.vrabel@citrix.com>
> >>> 
> >>> PRIVCMD_MMAPBATCH_V2 extends PRIVCMD_MMAPBATCH with an additional
> >>> field for reporting the error code for every frame that could not be
> >>> mapped.  libxc prefers PRIVCMD_MMAPBATCH_V2 over PRIVCMD_MMAPBATCH.
> >>> 
> >>> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> >>> ---
> >>> drivers/xen/privcmd.c |   99 +++++++++++++++++++++++++++++++++++++++---------
> >>> include/xen/privcmd.h |   23 +++++++++++-
> >>> 2 files changed, 102 insertions(+), 20 deletions(-)
> >>> 
> >>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> >>> index ccee0f1..c0e89e7 100644
> >>> --- a/drivers/xen/privcmd.c
> >>> +++ b/drivers/xen/privcmd.c
> >>> @@ -76,7 +76,7 @@ static void free_page_list(struct list_head *pages)
> >>> */
> >>> static int gather_array(struct list_head *pagelist,
> >>> 			unsigned nelem, size_t size,
> >>> -			void __user *data)
> >>> +			const void __user *data)
> >>> {
> >>> 	unsigned pageidx;
> >>> 	void *pagedata;
> >>> @@ -248,18 +248,37 @@ struct mmap_batch_state {
> >>> 	struct vm_area_struct *vma;
> >>> 	int err;
> >>> 
> >>> -	xen_pfn_t __user *user;
> >>> +	xen_pfn_t __user *user_mfn;
> >>> +	int __user *user_err;
> >>> };
> >>> 
> >>> static int mmap_batch_fn(void *data, void *state)
> >>> {
> >>> 	xen_pfn_t *mfnp = data;
> >>> 	struct mmap_batch_state *st = state;
> >>> +	int ret;
> >>> 
> >>> -	if (xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
> >>> -				       st->vma->vm_page_prot, st->domain) < 0) {
> >>> -		*mfnp |= 0xf0000000U;
> >>> -		st->err++;
> >>> +	ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
> >>> +					 st->vma->vm_page_prot, st->domain);
> >>> +	if (ret < 0) {
> >>> +		/*
> >>> +		 * Error reporting is a mess but userspace relies on
> >>> +		 * it behaving this way.
> >>> +		 *
> >>> +		 * V2 needs to a) return the result of each frame's
> >>> +		 * remap; and b) return -ENOENT if any frame failed
> >>> +		 * with -ENOENT.
> >>> +		 *
> >>> +		 * In this first pass the error code is saved by
> >>> +		 * overwriting the mfn and an error is indicated in
> >>> +		 * st->err.
> >>> +		 *
> >>> +		 * The second pass by mmap_return_errors() will write
> >>> +		 * the error codes to user space and get the right
> >>> +		 * ioctl return value.
> >>> +		 */
> >>> +		*(int *)mfnp = ret;
> >>> +		st->err = ret;
> >>> 	}
> >>> 	st->va += PAGE_SIZE;
> >>> 
> >>> @@ -270,16 +289,33 @@ static int mmap_return_errors(void *data, void *state)
> >>> {
> >>> 	xen_pfn_t *mfnp = data;
> >>> 	struct mmap_batch_state *st = state;
> >>> +	int ret;
> >>> +
> >>> +	if (st->user_err) {
> >>> +		int err = *(int *)mfnp;
> >>> +
> >>> +		if (err == -ENOENT)
> >>> +			st->err = err;
> >>> 
> >>> -	return put_user(*mfnp, st->user++);
> >>> +		return __put_user(err, st->user_err++);
> >>> +	} else {
> >>> +		xen_pfn_t mfn;
> >>> +
> >>> +		ret = __get_user(mfn, st->user_mfn);
> >>> +		if (ret < 0)
> >>> +			return ret;
> >>> +
> >>> +		mfn |= PRIVCMD_MMAPBATCH_MFN_ERROR;
> >>> +		return __put_user(mfn, st->user_mfn++);
> >>> +	}
> >>> }
> >>> 
> >>> static struct vm_operations_struct privcmd_vm_ops;
> >>> 
> >>> -static long privcmd_ioctl_mmap_batch(void __user *udata)
> >>> +static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
> >>> {
> >>> 	int ret;
> >>> -	struct privcmd_mmapbatch m;
> >>> +	struct privcmd_mmapbatch_v2 m;
> >>> 	struct mm_struct *mm = current->mm;
> >>> 	struct vm_area_struct *vma;
> >>> 	unsigned long nr_pages;
> >>> @@ -289,15 +325,31 @@ static long privcmd_ioctl_mmap_batch(void __user *udata)
> >>> 	if (!xen_initial_domain())
> >>> 		return -EPERM;
> >>> 
> >>> -	if (copy_from_user(&m, udata, sizeof(m)))
> >>> -		return -EFAULT;
> >>> +	switch (version) {
> >>> +	case 1:
> >>> +		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
> >>> +			return -EFAULT;
> >>> +		/* Returns per-frame error in m.arr. */
> >>> +		m.err = NULL;
> >>> +		if (!access_ok(VERIFY_WRITE, m.arr, m.num * sizeof(*m.arr)))
> >>> +			return -EFAULT;
> >>> +		break;
> >>> +	case 2:
> >>> +		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
> >>> +			return -EFAULT;
> >>> +		/* Returns per-frame error code in m.err. */
> >>> +		if (!access_ok(VERIFY_WRITE, m.err, m.num * (sizeof(*m.err))))
> >>> +			return -EFAULT;
> >>> +		break;
> >>> +	default:
> >>> +		return -EINVAL;
> >>> +	}
> >>> 
> >>> 	nr_pages = m.num;
> >>> 	if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
> >>> 		return -EINVAL;
> >>> 
> >>> -	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t),
> >>> -			   m.arr);
> >>> +	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);
> >>> 
> >>> 	if (ret || list_empty(&pagelist))
> >>> 		goto out;
> >>> @@ -325,12 +377,17 @@ static long privcmd_ioctl_mmap_batch(void __user *udata)
> >>> 
> >>> 	up_write(&mm->mmap_sem);
> >>> 
> >>> -	if (state.err > 0) {
> >>> -		state.user = m.arr;
> >>> +	if (state.err) {
> >>> +		state.err = 0;
> >>> +		state.user_mfn = (xen_pfn_t *)m.arr;
> >>> +		state.user_err = m.err;
> >>> 		ret = traverse_pages(m.num, sizeof(xen_pfn_t),
> >>> -			       &pagelist,
> >>> -			       mmap_return_errors, &state);
> >>> -	}
> >>> +				     &pagelist,
> >>> +				     mmap_return_errors, &state);
> >>> +		if (ret >= 0)
> >>> +			ret = state.err;
> >>> +	} else if (m.err)
> >>> +		__clear_user(m.err, m.num * sizeof(*m.err));
> >>> 
> >>> out:
> >>> 	free_page_list(&pagelist);
> >>> @@ -354,7 +411,11 @@ static long privcmd_ioctl(struct file *file,
> >>> 		break;
> >>> 
> >>> 	case IOCTL_PRIVCMD_MMAPBATCH:
> >>> -		ret = privcmd_ioctl_mmap_batch(udata);
> >>> +		ret = privcmd_ioctl_mmap_batch(udata, 1);
> >>> +		break;
> >>> +
> >>> +	case IOCTL_PRIVCMD_MMAPBATCH_V2:
> >>> +		ret = privcmd_ioctl_mmap_batch(udata, 2);
> >>> 		break;
> >>> 
> >>> 	default:
> >>> diff --git a/include/xen/privcmd.h b/include/xen/privcmd.h
> >>> index 17857fb..f60d75c 100644
> >>> --- a/include/xen/privcmd.h
> >>> +++ b/include/xen/privcmd.h
> >>> @@ -59,13 +59,32 @@ struct privcmd_mmapbatch {
> >>> 	int num;     /* number of pages to populate */
> >>> 	domid_t dom; /* target domain */
> >>> 	__u64 addr;  /* virtual address */
> >>> -	xen_pfn_t __user *arr; /* array of mfns - top nibble set on err */
> >>> +	xen_pfn_t __user *arr; /* array of mfns - or'd with
> >>> +				  PRIVCMD_MMAPBATCH_MFN_ERROR on err */
> >>> +};
> >>> +
> >>> +#define PRIVCMD_MMAPBATCH_MFN_ERROR 0xf0000000U
> >>> +
> >>> +struct privcmd_mmapbatch_v2 {
> >>> +	unsigned int num; /* number of pages to populate */
> >>> +	domid_t dom;      /* target domain */
> >>> +	__u64 addr;       /* virtual address */
> >>> +	const xen_pfn_t __user *arr; /* array of mfns */
> >>> +	int __user *err;  /* array of error codes */
> >>> };
> >>> 
> >>> /*
> >>> * @cmd: IOCTL_PRIVCMD_HYPERCALL
> >>> * @arg: &privcmd_hypercall_t
> >>> * Return: Value returned from execution of the specified hypercall.
> >>> + *
> >>> + * @cmd: IOCTL_PRIVCMD_MMAPBATCH_V2
> >>> + * @arg: &struct privcmd_mmapbatch_v2
> >>> + * Return: 0 on success (i.e., arg->err contains valid error codes for
> >>> + * each frame).  On an error other than a failed frame remap, -1 is
> >>> + * returned and errno is set to EINVAL, EFAULT etc.  As an exception,
> >>> + * if the operation was otherwise successful but any frame failed with
> >>> + * -ENOENT, then -1 is returned and errno is set to ENOENT.
> >>> */
> >>> #define IOCTL_PRIVCMD_HYPERCALL					\
> >>> 	_IOC(_IOC_NONE, 'P', 0, sizeof(struct privcmd_hypercall))
> >>> @@ -73,5 +92,7 @@ struct privcmd_mmapbatch {
> >>> 	_IOC(_IOC_NONE, 'P', 2, sizeof(struct privcmd_mmap))
> >>> #define IOCTL_PRIVCMD_MMAPBATCH					\
> >>> 	_IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch))
> >>> +#define IOCTL_PRIVCMD_MMAPBATCH_V2				\
> >>> +	_IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
> >>> 
> >>> #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
> >>> -- 
> >>> 1.7.2.5
> >>>