Re: Re: how to handle paged hypercall args?

[Olaf Hering <olaf@aepfle.de>]

On Thu, Nov 18, Keir Fraser wrote:

> I've done something along these lines now as xen-unstable:22402. It actually
> seems to work okay! So you can go ahead and use waitqueues in __hvm_copy()
> now.

This is my first attempt to do it.
It crashed Xen on the very first try in a spectacular way. But it
happend only once for some reason.
See my other mail.


Olaf

--- xen-unstable.hg-4.1.22447.orig/xen/arch/x86/hvm/hvm.c
+++ xen-unstable.hg-4.1.22447/xen/arch/x86/hvm/hvm.c
@@ -1986,69 +1986,117 @@ static enum hvm_copy_result __hvm_copy(
 enum hvm_copy_result hvm_copy_to_guest_phys(
     paddr_t paddr, void *buf, int size)
 {
-    return __hvm_copy(buf, paddr, size,
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, paddr, size,
                       HVMCOPY_to_guest | HVMCOPY_fault | HVMCOPY_phys,
-                      0);
+                      0)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 enum hvm_copy_result hvm_copy_from_guest_phys(
     void *buf, paddr_t paddr, int size)
 {
-    return __hvm_copy(buf, paddr, size,
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, paddr, size,
                       HVMCOPY_from_guest | HVMCOPY_fault | HVMCOPY_phys,
-                      0);
+                      0)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 enum hvm_copy_result hvm_copy_to_guest_virt(
     unsigned long vaddr, void *buf, int size, uint32_t pfec)
 {
-    return __hvm_copy(buf, vaddr, size,
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, vaddr, size,
                       HVMCOPY_to_guest | HVMCOPY_fault | HVMCOPY_virt,
-                      PFEC_page_present | PFEC_write_access | pfec);
+                      PFEC_page_present | PFEC_write_access | pfec)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 enum hvm_copy_result hvm_copy_from_guest_virt(
     void *buf, unsigned long vaddr, int size, uint32_t pfec)
 {
-    return __hvm_copy(buf, vaddr, size,
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, vaddr, size,
                       HVMCOPY_from_guest | HVMCOPY_fault | HVMCOPY_virt,
-                      PFEC_page_present | pfec);
+                      PFEC_page_present | pfec)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 enum hvm_copy_result hvm_fetch_from_guest_virt(
     void *buf, unsigned long vaddr, int size, uint32_t pfec)
 {
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
     if ( hvm_nx_enabled(current) )
         pfec |= PFEC_insn_fetch;
-    return __hvm_copy(buf, vaddr, size,
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, vaddr, size,
                       HVMCOPY_from_guest | HVMCOPY_fault | HVMCOPY_virt,
-                      PFEC_page_present | pfec);
+                      PFEC_page_present | pfec)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 enum hvm_copy_result hvm_copy_to_guest_virt_nofault(
     unsigned long vaddr, void *buf, int size, uint32_t pfec)
 {
-    return __hvm_copy(buf, vaddr, size,
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, vaddr, size,
                       HVMCOPY_to_guest | HVMCOPY_no_fault | HVMCOPY_virt,
-                      PFEC_page_present | PFEC_write_access | pfec);
+                      PFEC_page_present | PFEC_write_access | pfec)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 enum hvm_copy_result hvm_copy_from_guest_virt_nofault(
     void *buf, unsigned long vaddr, int size, uint32_t pfec)
 {
-    return __hvm_copy(buf, vaddr, size,
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, vaddr, size,
                       HVMCOPY_from_guest | HVMCOPY_no_fault | HVMCOPY_virt,
-                      PFEC_page_present | pfec);
+                      PFEC_page_present | pfec)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 enum hvm_copy_result hvm_fetch_from_guest_virt_nofault(
     void *buf, unsigned long vaddr, int size, uint32_t pfec)
 {
+    enum hvm_copy_result res;
+    struct waitqueue_head wq;
     if ( hvm_nx_enabled(current) )
         pfec |= PFEC_insn_fetch;
-    return __hvm_copy(buf, vaddr, size,
+    init_waitqueue_head(&wq);
+
+    wait_event(wq, (
+    res = __hvm_copy(buf, vaddr, size,
                       HVMCOPY_from_guest | HVMCOPY_no_fault | HVMCOPY_virt,
-                      PFEC_page_present | pfec);
+                      PFEC_page_present | pfec)) != HVMCOPY_gfn_paged_out);
+    return res;
 }
 
 unsigned long copy_to_user_hvm(void *to, const void *from, unsigned int len)