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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/2] x86/HVM: fix preemption handling in do_hvm_op() (try 2)
>-----Original Message-----
>From: Jan Beulich <JBeulich@xxxxxxxx>
>Date: Wed, Apr 2, 2014 at 1:09 AM
>Subject: [Xen-devel] [PATCH 1/2] x86/HVM: fix preemption handling in
>do_hvm_op() (try 2)
>To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
>Cc: Tim Deegan <tim@xxxxxxx>, Keir Fraser <keir@xxxxxxx>
>
>
>Just like previously done for some mem-op hypercalls, undo preemption
>using the interface structures (altering it in ways the caller may not
>expect) and replace it by storing the continuation point in the high bits of
>sub-
>operation argument.
As part of my PV mem_access work, I am moving HVMOP_set_mem_access in to
mem_access_memop() as XENMEM_access_op_set_access, to make it more generic. I
am not sure how to go about doing the preemption handling here. I am not able
to do something similar as the mem_access ops is a subarch_memory_op, so I was
thinking of using the interface structures but the above comment has me
worried. Is it not safe to do this for _set_mem_access op? I will send out an
RFC patch to make it clear as to what I am doing. Please take a look and advise
as to how I should proceed.
Thanks,
Aravindh
>This also changes the "nr" fields of struct xen_hvm_track_dirty_vram
>(operation already limited to 1Gb worth of pages) and struct
>xen_hvm_modified_memory to be only 32 bits wide, consistent with those of
>struct xen_set_mem{type,access}. If that's not acceptable for some reason,
>we'd need to shrink the HVMOP_op_bits (while still enforcing the [then
>higher] limit resulting from the need to be able to encode the continuation).
>
>Whether (and if so how) to adjust xc_hvm_track_dirty_vram(),
>xc_hvm_modified_memory(), xc_hvm_set_mem_type(), and
>xc_hvm_set_mem_access() to reflect the 32-bit restriction on "nr" is
>unclear: If the APIs need to remain stable, all four functions should probably
>check that there was no truncation. Preferably their parameters would be
>changed to uint32_t or unsigned int, though.
>
>Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>---
>v2: Avoid double increment of pfn in HVMOP_modified_memory and
> HVMOP_set_mem_type handling. Change preemption logic to also work
> for 32-bit callers. Drop unrelated cleanup.
>
>--- a/xen/arch/x86/hvm/hvm.c
>+++ b/xen/arch/x86/hvm/hvm.c
>@@ -4047,13 +4047,16 @@ static int hvm_replace_event_channel(str
> return 0;
> }
>
>+#define HVMOP_op_mask 0xff
>+
> long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
>
> {
> struct domain *curr_d = current->domain;
>+ unsigned long start_iter = op & ~HVMOP_op_mask;
> long rc = 0;
>
>- switch ( op )
>+ switch ( op &= HVMOP_op_mask )
> {
> case HVMOP_set_param:
> case HVMOP_get_param:
>@@ -4383,7 +4386,8 @@ long do_hvm_op(unsigned long op, XEN_GUE
> goto param_fail3;
>
> rc = -EINVAL;
>- if ( ((a.first_pfn + a.nr - 1) < a.first_pfn) ||
>+ if ( a.nr < start_iter ||
>+ ((a.first_pfn + a.nr - 1) < a.first_pfn) ||
> ((a.first_pfn + a.nr - 1) > domain_get_maximum_gpfn(d)) )
> goto param_fail3;
>
>@@ -4391,9 +4395,9 @@ long do_hvm_op(unsigned long op, XEN_GUE
> if ( !paging_mode_log_dirty(d) )
> goto param_fail3;
>
>- while ( a.nr > 0 )
>+ while ( a.nr > start_iter )
> {
>- unsigned long pfn = a.first_pfn;
>+ unsigned long pfn = a.first_pfn + start_iter;
> struct page_info *page;
>
> page = get_page_from_gfn(d, pfn, NULL, P2M_UNSHARE); @@ -
>4406,16 +4410,11 @@ long do_hvm_op(unsigned long op, XEN_GUE
> put_page(page);
> }
>
>- a.first_pfn++;
>- a.nr--;
>-
> /* Check for continuation if it's not the last interation */
>- if ( a.nr > 0 && hypercall_preempt_check() )
>+ if ( a.nr > ++start_iter && !(start_iter & HVMOP_op_mask) &&
>+ hypercall_preempt_check() )
> {
>- if ( __copy_to_guest(arg, &a, 1) )
>- rc = -EFAULT;
>- else
>- rc = -EAGAIN;
>+ rc = -EAGAIN;
> break;
> }
> }
>@@ -4497,16 +4496,17 @@ long do_hvm_op(unsigned long op, XEN_GUE
> goto param_fail4;
>
> rc = -EINVAL;
>- if ( ((a.first_pfn + a.nr - 1) < a.first_pfn) ||
>+ if ( a.nr < start_iter ||
>+ ((a.first_pfn + a.nr - 1) < a.first_pfn) ||
> ((a.first_pfn + a.nr - 1) > domain_get_maximum_gpfn(d)) )
> goto param_fail4;
>
> if ( a.hvmmem_type >= ARRAY_SIZE(memtype) )
> goto param_fail4;
>
>- while ( a.nr )
>+ while ( a.nr > start_iter )
> {
>- unsigned long pfn = a.first_pfn;
>+ unsigned long pfn = a.first_pfn + start_iter;
> p2m_type_t t;
> p2m_type_t nt;
> mfn_t mfn;
>@@ -4547,16 +4547,11 @@ long do_hvm_op(unsigned long op, XEN_GUE
> }
> put_gfn(d, pfn);
>
>- a.first_pfn++;
>- a.nr--;
>-
> /* Check for continuation if it's not the last interation */
>- if ( a.nr > 0 && hypercall_preempt_check() )
>+ if ( a.nr > ++start_iter && !(start_iter & HVMOP_op_mask) &&
>+ hypercall_preempt_check() )
> {
>- if ( __copy_to_guest(arg, &a, 1) )
>- rc = -EFAULT;
>- else
>- rc = -EAGAIN;
>+ rc = -EAGAIN;
> goto param_fail4;
> }
> }
>@@ -4590,19 +4585,17 @@ long do_hvm_op(unsigned long op, XEN_GUE
>
> rc = -EINVAL;
> if ( (a.first_pfn != ~0ull) &&
>- (((a.first_pfn + a.nr - 1) < a.first_pfn) ||
>+ (a.nr < start_iter ||
>+ ((a.first_pfn + a.nr - 1) < a.first_pfn) ||
> ((a.first_pfn + a.nr - 1) > domain_get_maximum_gpfn(d))) )
> goto param_fail5;
>
>- rc = p2m_set_mem_access(d, a.first_pfn, a.nr, a.hvmmem_access);
>+ rc = p2m_set_mem_access(d, a.first_pfn, a.nr, start_iter,
>+ HVMOP_op_mask, 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;
>+ start_iter = rc;
>+ rc = -EAGAIN;
> }
>
> param_fail5:
>@@ -4751,8 +4744,11 @@ long do_hvm_op(unsigned long op, XEN_GUE
> }
>
> if ( rc == -EAGAIN )
>- rc = hypercall_create_continuation(
>- __HYPERVISOR_hvm_op, "lh", op, arg);
>+ {
>+ ASSERT(!(start_iter & HVMOP_op_mask));
>+ rc = hypercall_create_continuation(__HYPERVISOR_hvm_op, "lh",
>+ op | start_iter, arg);
>+ }
>
> return rc;
> }
>--- a/xen/arch/x86/mm/p2m.c
>+++ b/xen/arch/x86/mm/p2m.c
>@@ -1334,13 +1334,13 @@ void p2m_mem_access_resume(struct domain
> /* Set access type for a region of pfns.
> * If start_pfn == -1ul, sets the default access type */ long
>p2m_set_mem_access(struct domain *d, unsigned long pfn, uint32_t nr,
>- hvmmem_access_t access)
>+ uint32_t start, uint32_t mask, hvmmem_access_t
>+ access)
> {
> struct p2m_domain *p2m = p2m_get_hostp2m(d);
> p2m_access_t a, _a;
> p2m_type_t t;
> mfn_t mfn;
>- long rc;
>+ long rc = 0;
>
> /* N.B. _not_ static: initializer depends on p2m->default_access */
> p2m_access_t memaccess[] = {
>@@ -1369,11 +1369,8 @@ long p2m_set_mem_access(struct domain *d
> return 0;
> }
>
>- if ( !nr )
>- return 0;
>-
> p2m_lock(p2m);
>- for ( ; ; ++pfn )
>+ for ( pfn += start; nr > start; ++pfn )
> {
> mfn = p2m->get_entry(p2m, pfn, &t, &_a, 0, NULL);
> if ( p2m->set_entry(p2m, pfn, mfn, PAGE_ORDER_4K, t, a) == 0 ) @@ -
>1383,9 +1380,9 @@ long p2m_set_mem_access(struct domain *d
> }
>
> /* Check for continuation if it's not the last interation. */
>- if ( !--nr || hypercall_preempt_check() )
>+ if ( nr > ++start && !(start & mask) &&
>+ hypercall_preempt_check() )
> {
>- rc = nr;
>+ rc = start;
> break;
> }
> }
>--- 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 */ -long
>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,
>+ uint32_t start, uint32_t mask, hvmmem_access_t
>+access);
>
> /* Get access type for a pfn
> * If pfn == -1ul, gets the default access type */
>--- a/xen/include/public/hvm/hvm_op.h
>+++ b/xen/include/public/hvm/hvm_op.h
>@@ -90,10 +90,10 @@ typedef enum {
> struct xen_hvm_track_dirty_vram {
> /* Domain to be tracked. */
> domid_t domid;
>+ /* Number of pages to track. */
>+ uint32_t nr;
> /* First pfn to track. */
> uint64_aligned_t first_pfn;
>- /* Number of pages to track. */
>- uint64_aligned_t nr;
> /* OUT variable. */
> /* Dirty bitmap buffer. */
> XEN_GUEST_HANDLE_64(uint8) dirty_bitmap; @@ -106,10 +106,10 @@
>DEFINE_XEN_GUEST_HANDLE(xen_hvm_track_di
> struct xen_hvm_modified_memory {
> /* Domain to be updated. */
> domid_t domid;
>+ /* Number of pages. */
>+ uint32_t nr;
> /* First pfn. */
> uint64_aligned_t first_pfn;
>- /* Number of pages. */
>- uint64_aligned_t nr;
> };
> typedef struct xen_hvm_modified_memory xen_hvm_modified_memory_t;
>DEFINE_XEN_GUEST_HANDLE(xen_hvm_modified_memory_t);
>
>
>
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