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Date: Wed, 18 Dec 2013 16:21:50 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc: xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
mukesh.rathor@...cle.com, jbeulich@...e.com
Subject: Re: [Xen-devel] [PATCH v11 10/12] xen/pvh: Piggyback on PVHVM for
grant driver.
On Wed, Dec 18, 2013 at 06:46:56PM +0000, Stefano Stabellini wrote:
> 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@...cle.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.
Yeah, that would work nicely too. Thought we would have to store the
size somewhere. Maybe a struct then.
struct xlat_grant_frames {
int nr;
xen_pfn_t *array;
struct page *page;
};
>
>
> > + xatp.gpfn = pte_mfn(*pte);
>
> Do you actually need the mfn here? Don't you just need the pfn?
Just (pte.pte & ~PAGE_FLAGS) >> PAGE_SHIFT.
>
>
>
> > + }
> > 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))
Hmm, I would rather actually keep that until I fix the underlaying issue
of why v2 can't be used. And then we can get rid of this workaround.
>
>
> > 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.
<nods>
Actually, looking at how the xen-platform-pci does it. I am wondering
if that can be just made in one function that will do the right
thing.
Can the xen-platform-pci use balloon pages instead of the MMIO BARs?
Or would that be a waste of memory?
>
>
> > 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.
<nods> And have some early init that sets this up.
>
>
> > 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.
Right. Thanks for reminding me!
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