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SubjectRe: [Xen-devel] [PATCH v11 10/12] xen/pvh: Piggyback on PVHVM for grant driver.
On Tue, 17 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.
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> drivers/xen/gntdev.c | 2 +-
> drivers/xen/grant-table.c | 80 ++++++++++++++++++++++++++++++++++++++++++----
> drivers/xen/platform-pci.c | 2 +-
> include/xen/grant_table.h | 2 +-
> 4 files changed, 76 insertions(+), 10 deletions(-)
>
> 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 aa846a4..c0ded9f 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -47,6 +47,7 @@
> #include <xen/interface/xen.h>
> #include <xen/page.h>
> #include <xen/grant_table.h>
> +#include <xen/balloon.h>
> #include <xen/interface/memory.h>
> #include <xen/hvc-console.h>
> #include <xen/swiotlb-xen.h>
> @@ -66,8 +67,8 @@ static unsigned int boot_max_nr_grant_frames;
> static int gnttab_free_count;
> static grant_ref_t gnttab_free_head;
> static DEFINE_SPINLOCK(gnttab_list_lock);
> -unsigned long xen_hvm_resume_frames;
> -EXPORT_SYMBOL_GPL(xen_hvm_resume_frames);
> +unsigned long xen_auto_xlat_grant_frames;
> +EXPORT_SYMBOL_GPL(xen_auto_xlat_grant_frames);
>
> static union {
> struct grant_entry_v1 *v1;
> @@ -1060,7 +1061,7 @@ 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;
> @@ -1069,10 +1070,24 @@ static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
> * index, ensuring that the table will grow only once.
> */
> do {
> + unsigned long vaddr;
> + unsigned int level;
> + pte_t *pte;
> +
> xatp.domid = DOMID_SELF;
> xatp.idx = i;
> xatp.space = XENMAPSPACE_grant_table;
> - xatp.gpfn = (xen_hvm_resume_frames >> PAGE_SHIFT) + i;
> +
> + /*
> + * Don't assume the memory is contingous. Lookup each.
> + */
> + vaddr = xen_auto_xlat_grant_frames + (i * PAGE_SIZE);
> + if (xen_hvm_domain())
> + xatp.gpfn = vaddr >> PAGE_SHIFT;
> + else {
> + pte = lookup_address(vaddr, &level);

lookup_address is x86 only. I added an empty implementation under
arch/arm to be able to compile stuff under drivers/xen but I would like
to get rid of it.
If you can't find a way to replace lookup_address with something that
works on arm and arm64 too, you could always turn
xen_auto_xlat_grant_frames into an array and store the pfns there.


> + xatp.gpfn = pte_mfn(*pte);

Do you actually need the mfn here? Don't you just need the pfn?



> + }
> rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
> if (rc != 0) {
> pr_warn("grant table add_to_physmap failed, err=%d\n",
> @@ -1135,7 +1150,7 @@ static void gnttab_request_version(void)
> int rc;
> struct gnttab_set_version gsv;
>
> - if (xen_hvm_domain())
> + if (xen_hvm_domain() || xen_feature(XENFEAT_auto_translated_physmap))

just turn this to

if (xen_feature(XENFEAT_auto_translated_physmap))


> gsv.version = 1;
> else
> gsv.version = 2;
> @@ -1161,6 +1176,46 @@ static void gnttab_request_version(void)
> pr_info("Grant tables using version %d layout\n", grant_table_version);
> }
>
> +static int xlated_setup_gnttab_pages(unsigned long nr_grant_frames,
> + unsigned long max, void *addr)
> +{
> + struct page **pages;
> + unsigned long *pfns;
> + int rc, i;
> +
> + 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, max, addr);
> +
> + kfree(pages);
> + kfree(pfns);
> + 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);
> + return rc;
> + }
> + return rc;
> +}

Please move this function somewhere under arch/x86/xen and call it from
xen_start_kernel, it doesn't belong to common code.


> static int gnttab_setup(void)
> {
> unsigned int max_nr_gframes;
> @@ -1169,15 +1224,26 @@ static int gnttab_setup(void)
> if (max_nr_gframes < nr_grant_frames)
> return -ENOSYS;
>
> + if (xen_feature(XENFEAT_auto_translated_physmap) && !xen_auto_xlat_grant_frames) {
> + /*
> + * xen_auto_xlat_grant_frames is setup for PVHVM by
> + * alloc_xen_mmio by the time this is called.
> + */
> + int rc = xlated_setup_gnttab_pages(max_nr_gframes, max_nr_gframes,
> + &gnttab_shared.addr);
> + if (rc)
> + return rc;
> + xen_auto_xlat_grant_frames = (unsigned long)gnttab_shared.addr;
> + }

I think you should do this from arch/x86/xen. When gnttab_setup is
called in your guest, xen_auto_xlat_grant_frames should have already
been setup correctly.


> if (xen_pv_domain())
> return gnttab_map(0, nr_grant_frames - 1);
>
> if (gnttab_shared.addr == NULL) {
> - gnttab_shared.addr = xen_remap(xen_hvm_resume_frames,
> + gnttab_shared.addr = xen_remap(xen_auto_xlat_grant_frames,
> PAGE_SIZE * max_nr_gframes);
> if (gnttab_shared.addr == NULL) {
> pr_warn("Failed to ioremap gnttab share frames (addr=0x%08lx)!\n",
> - xen_hvm_resume_frames);
> + xen_auto_xlat_grant_frames);
> return -ENOMEM;
> }
> }
> diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
> index 2f3528e..44bc5a6 100644
> --- a/drivers/xen/platform-pci.c
> +++ b/drivers/xen/platform-pci.c
> @@ -154,7 +154,7 @@ static int platform_pci_init(struct pci_dev *pdev,
> }
>
> max_nr_gframes = gnttab_max_grant_frames();
> - xen_hvm_resume_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
> + xen_auto_xlat_grant_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
> ret = gnttab_init();
> if (ret)
> goto out;
> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> index 694dcaf..24280ac 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -178,7 +178,7 @@ int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
> grant_status_t **__shared);
> void arch_gnttab_unmap(void *shared, unsigned long nr_gframes);
>
> -extern unsigned long xen_hvm_resume_frames;
> +extern unsigned long xen_auto_xlat_grant_frames;
> unsigned int gnttab_max_grant_frames(void);
>
> #define gnttab_map_vaddr(map) ((void *)(map.host_virt_addr))

You need to s/xen_hvm_resume_frames/xen_auto_xlat_grant_frames under
arch/arm/xen too.


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