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Date:	Sun, 5 Jan 2014 18:20:15 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>,
	<boris.ostrovsky@...cle.com>, <stefano.stabellini@...citrix.com>,
	<david.vrabel@...rix.com>, <hpa@...or.com>
Subject: Re: [PATCH v13 17/19] xen/pvh: Piggyback on PVHVM for grant driver
 (v4)

On Fri, 3 Jan 2014, Konrad Rzeszutek Wilk wrote:
> In PVH the shared grant frame is the PFN and not MFN,
> hence its mapped via the same code path as HVM.
> 
> The allocation of the grant frame is done differently - we
> do not use the early platform-pci driver and have an
> ioremap area - instead we use balloon memory and stitch
> all of the non-contingous pages in a virtualized area.
> 
> That means when we call the hypervisor to replace the GMFN
> with a XENMAPSPACE_grant_table type, we need to lookup the
> old PFN for every iteration instead of assuming a flat
> contingous PFN allocation.
> 
> Lastly, we only use v1 for grants. This is because PVHVM
> is not able to use v2 due to no XENMEM_add_to_physmap
> calls on the error status page (see commit
> 69e8f430e243d657c2053f097efebc2e2cd559f0
>  xen/granttable: Disable grant v2 for HVM domains.)
> 
> Until that is implemented this workaround has to
> be in place.
> 
> Also per suggestions by Stefano utilize the PVHVM paths
> as they share common functionality.
> 
> v2 of this patch moves most of the PVH code out in the
> arch/x86/xen/grant-table driver and touches only minimally
> the generic driver.
> 
> v3, v4: fixes us some of the code due to earlier patches.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Acked-by: Stefano Stabellini <stefano.stabellini@...citrix.com>


>  arch/x86/xen/grant-table.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/xen/gntdev.c       |  2 +-
>  drivers/xen/grant-table.c  |  9 ++++---
>  3 files changed, 68 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
> index 3a5f55d..2d71979 100644
> --- a/arch/x86/xen/grant-table.c
> +++ b/arch/x86/xen/grant-table.c
> @@ -125,3 +125,65 @@ void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
>  	apply_to_page_range(&init_mm, (unsigned long)shared,
>  			    PAGE_SIZE * nr_gframes, unmap_pte_fn, NULL);
>  }
> +#ifdef CONFIG_XEN_PVH
> +#include <xen/balloon.h>
> +#include <xen/events.h>
> +#include <linux/slab.h>
> +static int __init xlated_setup_gnttab_pages(void)
> +{
> +	struct page **pages;
> +	xen_pfn_t *pfns;
> +	int rc;
> +	unsigned int i;
> +	unsigned long nr_grant_frames = gnttab_max_grant_frames();
> +
> +	BUG_ON(nr_grant_frames == 0);
> +	pages = kcalloc(nr_grant_frames, sizeof(pages[0]), GFP_KERNEL);
> +	if (!pages)
> +		return -ENOMEM;
> +
> +	pfns = kcalloc(nr_grant_frames, sizeof(pfns[0]), GFP_KERNEL);
> +	if (!pfns) {
> +		kfree(pages);
> +		return -ENOMEM;
> +	}
> +	rc = alloc_xenballooned_pages(nr_grant_frames, pages, 0 /* lowmem */);
> +	if (rc) {
> +		pr_warn("%s Couldn't balloon alloc %ld pfns rc:%d\n", __func__,
> +			nr_grant_frames, rc);
> +		kfree(pages);
> +		kfree(pfns);
> +		return rc;
> +	}
> +	for (i = 0; i < nr_grant_frames; i++)
> +		pfns[i] = page_to_pfn(pages[i]);
> +
> +	rc = arch_gnttab_map_shared(pfns, nr_grant_frames, nr_grant_frames,
> +				    &xen_auto_xlat_grant_frames.vaddr);
> +
> +	kfree(pages);
> +	if (rc) {
> +		pr_warn("%s Couldn't map %ld pfns rc:%d\n", __func__,
> +			nr_grant_frames, rc);
> +		free_xenballooned_pages(nr_grant_frames, pages);
> +		kfree(pfns);
> +		return rc;
> +	}
> +
> +	xen_auto_xlat_grant_frames.pfn = pfns;
> +	xen_auto_xlat_grant_frames.count = nr_grant_frames;
> +
> +	return 0;
> +}
> +
> +static int __init xen_pvh_gnttab_setup(void)
> +{
> +	if (!xen_pvh_domain())
> +		return -ENODEV;
> +
> +	return xlated_setup_gnttab_pages();
> +}
> +/* Call it _before_ __gnttab_init as we need to initialize the
> + * xen_auto_xlat_grant_frames first. */
> +core_initcall(xen_pvh_gnttab_setup);
> +#endif
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index e41c79c..073b4a1 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -846,7 +846,7 @@ static int __init gntdev_init(void)
>  	if (!xen_domain())
>  		return -ENODEV;
>  
> -	use_ptemod = xen_pv_domain();
> +	use_ptemod = !xen_feature(XENFEAT_auto_translated_physmap);
>  
>  	err = misc_register(&gntdev_miscdev);
>  	if (err != 0) {
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 6c78fd21..3d04c1c 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -1108,7 +1108,7 @@ static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
>  	unsigned int nr_gframes = end_idx + 1;
>  	int rc;
>  
> -	if (xen_hvm_domain()) {
> +	if (xen_feature(XENFEAT_auto_translated_physmap)) {
>  		struct xen_add_to_physmap xatp;
>  		unsigned int i = end_idx;
>  		rc = 0;
> @@ -1184,7 +1184,7 @@ static void gnttab_request_version(void)
>  	int rc;
>  	struct gnttab_set_version gsv;
>  
> -	if (xen_hvm_domain())
> +	if (xen_feature(XENFEAT_auto_translated_physmap))
>  		gsv.version = 1;
>  	else
>  		gsv.version = 2;
> @@ -1328,5 +1328,6 @@ static int __gnttab_init(void)
>  
>  	return gnttab_init();
>  }
> -
> -core_initcall(__gnttab_init);
> +/* Starts after core_initcall so that xen_pvh_gnttab_setup can be called
> + * beforehand to initialize xen_auto_xlat_grant_frames. */
> +core_initcall_sync(__gnttab_init);
> -- 
> 1.8.3.1
> 
--
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