Re: query the page type of a hvm page from within a hvm guest

[Olaf Hering <olaf@aepfle.de>]

On Mon, May 02, Jan Beulich wrote:

> >>> On 02.05.11 at 11:17, Olaf Hering <olaf@aepfle.de> wrote:
> > On Thu, Apr 07, Tim Deegan wrote:
> > 
> >> Hi, 
> >> 
> >> At 11:12 +0100 on 07 Apr (1302174722), Olaf Hering wrote:
> >> > If the crash kernel had a way to ask the hypervisor wether a specific
> >> > guest gfn is ballooned and thus backed by ram, the load issue would not
> >> > happen.  There seems to be no interface to query the type of a guest gfn
> >> > from within the hvm guest.
> >> > 
> >> > Any ideas how to implement that?
> >> > I see HVMOP_set_mem_type, but no HVMOP_get_mem_type.
> >> 
> >> Feel free to add HVMOP_get_mem_type.  I don't think any great harm can
> >> come from allowing the guest to query its own memory status.
> > 
> > This version works for me, tested with xen 4.0.1 and SLES11 SP1 kernel.
> > The actual kernel interface needs to be send to lkml.
> > 
> > Is there an u8 for padding required after mem_type in xen_hvm_get_mem_type?
> > Should HVMOP_get_mem_type just check for p2m_is_mmio() or return every
> > possible hvmmem_type_t value?
> 
> I'd say the latter, even if you don't use it at present.

So what about this version then?



---
 unmodified_drivers/linux-2.6/platform-pci/platform-pci.c |   36 +++++++++++++++
 xen/arch/ia64/vmx/vmx_hypercall.c                        |    1
 xen/arch/x86/hvm/hvm.c                                   |   27 +++++++++++
 xen/include/public/hvm/hvm_op.h                          |   25 ++++++++--
 4 files changed, 84 insertions(+), 5 deletions(-)

diff -r 2f08c89b767d unmodified_drivers/linux-2.6/platform-pci/platform-pci.c
--- a/unmodified_drivers/linux-2.6/platform-pci/platform-pci.c	Wed Apr 20 17:13:08 2011 +0100
+++ b/unmodified_drivers/linux-2.6/platform-pci/platform-pci.c	Mon May 02 17:42:57 2011 +0200
@@ -349,6 +349,32 @@ static int check_platform_magic(struct d
 	return -ENODEV;
 }
 
+#ifdef HAVE_OLDMEM_PFN_IS_RAM
+static int xen_oldmem_pfn_is_ram(unsigned long pfn)
+{
+	struct xen_hvm_get_mem_type a;
+	int ret;
+
+	a.domid = DOMID_SELF;
+	a.pfn = pfn;
+	if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a))
+		return -ENXIO;
+
+	switch (a.mem_type) {
+		case HVMMEM_mmio_dm:
+			ret = 0;
+			break;
+		case HVMMEM_ram_rw:
+		case HVMMEM_ram_ro:
+		default:
+			ret = 1;
+			break;
+	}
+
+	return ret;
+}
+#endif
+
 static int __devinit platform_pci_init(struct pci_dev *pdev,
 				       const struct pci_device_id *ent)
 {
@@ -417,6 +443,9 @@ static int __devinit platform_pci_init(s
 	if ((ret = xen_panic_handler_init()))
 		goto out;
 
+#ifdef HAVE_OLDMEM_PFN_IS_RAM
+	register_oldmem_pfn_is_ram(&xen_oldmem_pfn_is_ram);
+#endif
  out:
 	if (ret) {
 		pci_release_region(pdev, 0);
diff -r 2f08c89b767d xen/arch/ia64/vmx/vmx_hypercall.c
--- a/xen/arch/ia64/vmx/vmx_hypercall.c	Wed Apr 20 17:13:08 2011 +0100
+++ b/xen/arch/ia64/vmx/vmx_hypercall.c	Mon May 02 17:42:57 2011 +0200
@@ -217,6 +217,7 @@ do_hvm_op(unsigned long op, XEN_GUEST_HA
         break;
     }
 
+    case HVMOP_get_mem_type:
     case HVMOP_set_mem_type:
     case HVMOP_set_mem_access:
     case HVMOP_get_mem_access:
diff -r 2f08c89b767d xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c	Wed Apr 20 17:13:08 2011 +0100
+++ b/xen/arch/x86/hvm/hvm.c	Mon May 02 17:42:57 2011 +0200
@@ -3676,6 +3676,37 @@ long do_hvm_op(unsigned long op, XEN_GUE
         break;
     }
 
+    case HVMOP_get_mem_type:
+    {
+        struct xen_hvm_get_mem_type a;
+        struct domain *d;
+        p2m_type_t t;
+
+        if ( copy_from_guest(&a, arg, 1) )
+            return -EFAULT;
+
+        rc = rcu_lock_remote_target_domain_by_id(a.domid, &d);
+        if ( rc != 0 )
+            return rc;
+
+        rc = -EINVAL;
+        if ( is_hvm_domain(d) )
+        {
+            gfn_to_mfn_unshare(p2m_get_hostp2m(d), a.pfn, &t, 0);
+            if ( p2m_is_mmio(t) )
+                a.mem_type =  HVMMEM_mmio_dm;
+	    else if ( p2m_is_readonly(t) )
+                a.mem_type =  HVMMEM_ram_ro;
+	    else if ( p2m_is_ram(t) )
+                a.mem_type =  HVMMEM_ram_rw;
+            else
+                a.mem_type =  HVMMEM_mmio_dm;
+            rc = copy_to_guest(arg, &a, 1) ? -EFAULT : 0;
+        }
+        rcu_unlock_domain(d);
+        break;
+    }
+
     case HVMOP_set_mem_type:
     {
         struct xen_hvm_set_mem_type a;
diff -r 2f08c89b767d xen/include/public/hvm/hvm_op.h
--- a/xen/include/public/hvm/hvm_op.h	Wed Apr 20 17:13:08 2011 +0100
+++ b/xen/include/public/hvm/hvm_op.h	Mon May 02 17:42:57 2011 +0200
@@ -76,6 +76,12 @@ DEFINE_XEN_GUEST_HANDLE(xen_hvm_set_pci_
 /* Flushes all VCPU TLBs: @arg must be NULL. */
 #define HVMOP_flush_tlbs          5
 
+typedef enum {
+    HVMMEM_ram_rw,             /* Normal read/write guest RAM */
+    HVMMEM_ram_ro,             /* Read-only; writes are discarded */
+    HVMMEM_mmio_dm,            /* Reads and write go to the device model */
+} hvmmem_type_t;
+
 /* Following tools-only interfaces may change in future. */
 #if defined(__XEN__) || defined(__XEN_TOOLS__)
 
@@ -109,11 +115,6 @@ typedef struct xen_hvm_modified_memory x
 DEFINE_XEN_GUEST_HANDLE(xen_hvm_modified_memory_t);
 
 #define HVMOP_set_mem_type    8
-typedef enum {
-    HVMMEM_ram_rw,             /* Normal read/write guest RAM */
-    HVMMEM_ram_ro,             /* Read-only; writes are discarded */
-    HVMMEM_mmio_dm,            /* Reads and write go to the device model */
-} hvmmem_type_t;
 /* Notify that a region of memory is to be treated in a specific way. */
 struct xen_hvm_set_mem_type {
     /* Domain to be updated. */
@@ -223,6 +224,20 @@ struct xen_hvm_inject_trap {
 typedef struct xen_hvm_inject_trap xen_hvm_inject_trap_t;
 DEFINE_XEN_GUEST_HANDLE(xen_hvm_inject_trap_t);
 
+#define HVMOP_get_mem_type    15
+/* Return hvmmem_type_t for the specified pfn. */
+struct xen_hvm_get_mem_type {
+    /* Domain to be queried. */
+    domid_t domid;
+    /* OUT variable. */
+    uint8_t mem_type;
+    /* IN variable. */
+    uint64_t pfn;
+};
+typedef struct xen_hvm_get_mem_type xen_hvm_get_mem_type_t;
+DEFINE_XEN_GUEST_HANDLE(xen_hvm_get_mem_type_t);
+
+
 #endif /* defined(__XEN__) || defined(__XEN_TOOLS__) */
 
 #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */