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x86: enforce preemption in HVM_set_mem_access / p2m_set_mem_access()
Processing up to 4G PFNs may take almost arbitrarily long, so
preemption is needed here.
This is XSA-89.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Tim Deegan <tim@xen.org>
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4593,6 +4593,15 @@ long do_hvm_op(unsigned long op, XEN_GUE
goto param_fail5;
rc = p2m_set_mem_access(d, a.first_pfn, a.nr, a.hvmmem_access);
+ if ( rc > 0 )
+ {
+ a.first_pfn += a.nr - rc;
+ a.nr = rc;
+ if ( __copy_to_guest(arg, &a, 1) )
+ rc = -EFAULT;
+ else
+ rc = -EAGAIN;
+ }
param_fail5:
rcu_unlock_domain(d);
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1333,15 +1333,14 @@ void p2m_mem_access_resume(struct domain
/* Set access type for a region of pfns.
* If start_pfn == -1ul, sets the default access type */
-int p2m_set_mem_access(struct domain *d, unsigned long start_pfn,
- uint32_t nr, hvmmem_access_t access)
+long p2m_set_mem_access(struct domain *d, unsigned long pfn, uint32_t nr,
+ hvmmem_access_t access)
{
struct p2m_domain *p2m = p2m_get_hostp2m(d);
- unsigned long pfn;
p2m_access_t a, _a;
p2m_type_t t;
mfn_t mfn;
- int rc = 0;
+ long rc;
/* N.B. _not_ static: initializer depends on p2m->default_access */
p2m_access_t memaccess[] = {
@@ -1364,14 +1363,17 @@ int p2m_set_mem_access(struct domain *d,
a = memaccess[access];
/* If request to set default access */
- if ( start_pfn == ~0ull )
+ if ( pfn == ~0ul )
{
p2m->default_access = a;
return 0;
}
+ if ( !nr )
+ return 0;
+
p2m_lock(p2m);
- for ( pfn = start_pfn; pfn < start_pfn + nr; pfn++ )
+ for ( ; ; ++pfn )
{
mfn = p2m->get_entry(p2m, pfn, &t, &_a, 0, NULL);
if ( p2m->set_entry(p2m, pfn, mfn, PAGE_ORDER_4K, t, a) == 0 )
@@ -1379,6 +1381,13 @@ int p2m_set_mem_access(struct domain *d,
rc = -ENOMEM;
break;
}
+
+ /* Check for continuation if it's not the last interation. */
+ if ( !--nr || hypercall_preempt_check() )
+ {
+ rc = nr;
+ break;
+ }
}
p2m_unlock(p2m);
return rc;
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -576,8 +576,8 @@ void p2m_mem_access_resume(struct domain
/* Set access type for a region of pfns.
* If start_pfn == -1ul, sets the default access type */
-int p2m_set_mem_access(struct domain *d, unsigned long start_pfn,
- uint32_t nr, hvmmem_access_t access);
+long p2m_set_mem_access(struct domain *d, unsigned long start_pfn,
+ uint32_t nr, hvmmem_access_t access);
/* Get access type for a pfn
* If pfn == -1ul, gets the default access type */
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