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Date: Fri, 3 Jan 2014 17:26:39 +0000
From: Stefano Stabellini <stefano.stabellini@...citrix.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC: <linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>,
<boris.ostrovsky@...cle.com>, <david.vrabel@...rix.com>,
<stefano.stabellini@...citrix.com>, <mukesh.rathor@...cle.com>
Subject: Re: [PATCH v12 15/18] xen/pvh: Piggyback on PVHVM for grant driver
(v2)
On Tue, 31 Dec 2013, 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.
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
> arch/x86/xen/grant-table.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++
> drivers/xen/gntdev.c | 2 +-
> drivers/xen/grant-table.c | 13 ++++++----
> 3 files changed, 73 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
> index 3a5f55d..040e064 100644
> --- a/arch/x86/xen/grant-table.c
> +++ b/arch/x86/xen/grant-table.c
> @@ -125,3 +125,67 @@ 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_PVHVM
> +#include <xen/balloon.h>
> +#include <linux/slab.h>
> +static int __init xlated_setup_gnttab_pages(void)
> +{
> + struct page **pages;
> + xen_pfn_t *pfns;
> + int rc, 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,
> + (void *)&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;
> +}
Unfortunately this way pfns is leaked. Can we safely free it or is it
reused at resume time?
> +static int __init xen_pvh_gnttab_setup(void)
> +{
> + if (!xen_domain())
> + return -ENODEV;
> +
> + if (!xen_pv_domain())
> + return -ENODEV;
> +
> + if (!xen_feature(XENFEAT_auto_translated_physmap))
> + return -ENODEV;
> +
> + return xlated_setup_gnttab_pages();
> +}
> +core_initcall(xen_pvh_gnttab_setup); /* Call it _before_ __gnttab_init */
> +#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 b117fd6..2fa3a4c 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -1098,7 +1098,7 @@ 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;
> @@ -1174,7 +1174,7 @@ 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;
> @@ -1210,8 +1210,11 @@ static int gnttab_setup(void)
>
> if (xen_feature(XENFEAT_auto_translated_physmap) && gnttab_shared.addr == NULL)
> {
> - gnttab_shared.addr = xen_remap(xen_auto_xlat_grant_frames.vaddr,
> - PAGE_SIZE * max_nr_gframes);
> + if (xen_hvm_domain()) {
> + gnttab_shared.addr = xen_remap(xen_auto_xlat_grant_frames.vaddr,
> + PAGE_SIZE * max_nr_gframes);
> + } else
> + gnttab_shared.addr = xen_auto_xlat_grant_frames.vaddr;
> if (gnttab_shared.addr == NULL) {
> pr_warn("Failed to ioremap gnttab share frames (addr=0x%08lx)!\n",
> xen_auto_xlat_grant_frames.vaddr);
> @@ -1320,4 +1323,4 @@ static int __gnttab_init(void)
> return gnttab_init();
> }
>
> -core_initcall(__gnttab_init);
> +core_initcall_sync(__gnttab_init);
--
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