From: "Jan Beulich" <JBeulich@suse.com>
To: xen-devel <xen-devel@lists.xenproject.org>
Cc: Tim Deegan <tim@xen.org>
Subject: [PATCH 2/2] x86/shadow: avoid extra local array variable
Date: Thu, 10 Mar 2016 03:13:40 -0700 [thread overview]
Message-ID: <56E156E402000078000DB2BE@prv-mh.provo.novell.com> (raw)
In-Reply-To: <56E1555002000078000DB293@prv-mh.provo.novell.com>
[-- Attachment #1: Type: text/plain, Size: 6445 bytes --]
mfns[2] was there just because struct sh_emulate_ctxt's two MFN values
can't be used to hand to vmap(). Making the structure fields an array
avoids the extra copying.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -1746,11 +1746,11 @@ void *sh_emulate_map_dest(struct vcpu *v
struct domain *d = v->domain;
void *map;
- sh_ctxt->mfn1 = emulate_gva_to_mfn(v, vaddr, sh_ctxt);
- if ( !mfn_valid(sh_ctxt->mfn1) )
- return ((mfn_x(sh_ctxt->mfn1) == BAD_GVA_TO_GFN) ?
+ sh_ctxt->mfn[0] = emulate_gva_to_mfn(v, vaddr, sh_ctxt);
+ if ( !mfn_valid(sh_ctxt->mfn[0]) )
+ return ((mfn_x(sh_ctxt->mfn[0]) == BAD_GVA_TO_GFN) ?
MAPPING_EXCEPTION :
- (mfn_x(sh_ctxt->mfn1) == READONLY_GFN) ?
+ (mfn_x(sh_ctxt->mfn[0]) == READONLY_GFN) ?
MAPPING_SILENT_FAIL : MAPPING_UNHANDLEABLE);
#ifndef NDEBUG
@@ -1767,39 +1767,36 @@ void *sh_emulate_map_dest(struct vcpu *v
/* Unaligned writes mean probably this isn't a pagetable. */
if ( vaddr & (bytes - 1) )
- sh_remove_shadows(d, sh_ctxt->mfn1, 0, 0 /* Slow, can fail. */ );
+ sh_remove_shadows(d, sh_ctxt->mfn[0], 0, 0 /* Slow, can fail. */ );
if ( likely(((vaddr + bytes - 1) & PAGE_MASK) == (vaddr & PAGE_MASK)) )
{
/* Whole write fits on a single page. */
- sh_ctxt->mfn2 = _mfn(INVALID_MFN);
- map = map_domain_page(sh_ctxt->mfn1) + (vaddr & ~PAGE_MASK);
+ sh_ctxt->mfn[1] = _mfn(INVALID_MFN);
+ map = map_domain_page(sh_ctxt->mfn[0]) + (vaddr & ~PAGE_MASK);
}
- else
+ else if ( !is_hvm_domain(d) )
{
- mfn_t mfns[2];
-
/*
* Cross-page emulated writes are only supported for HVM guests;
* PV guests ought to know better.
*/
- if ( !is_hvm_domain(d) )
- return MAPPING_UNHANDLEABLE;
-
+ return MAPPING_UNHANDLEABLE;
+ }
+ else
+ {
/* This write crosses a page boundary. Translate the second page. */
- sh_ctxt->mfn2 = emulate_gva_to_mfn(v, vaddr + bytes, sh_ctxt);
- if ( !mfn_valid(sh_ctxt->mfn2) )
- return ((mfn_x(sh_ctxt->mfn2) == BAD_GVA_TO_GFN) ?
+ sh_ctxt->mfn[1] = emulate_gva_to_mfn(v, vaddr + bytes, sh_ctxt);
+ if ( !mfn_valid(sh_ctxt->mfn[1]) )
+ return ((mfn_x(sh_ctxt->mfn[1]) == BAD_GVA_TO_GFN) ?
MAPPING_EXCEPTION :
- (mfn_x(sh_ctxt->mfn2) == READONLY_GFN) ?
+ (mfn_x(sh_ctxt->mfn[1]) == READONLY_GFN) ?
MAPPING_SILENT_FAIL : MAPPING_UNHANDLEABLE);
/* Cross-page writes mean probably not a pagetable. */
- sh_remove_shadows(d, sh_ctxt->mfn2, 0, 0 /* Slow, can fail. */ );
+ sh_remove_shadows(d, sh_ctxt->mfn[1], 0, 0 /* Slow, can fail. */ );
- mfns[0] = sh_ctxt->mfn1;
- mfns[1] = sh_ctxt->mfn2;
- map = vmap(mfns, 2);
+ map = vmap(sh_ctxt->mfn, 2);
if ( !map )
return MAPPING_UNHANDLEABLE;
map += (vaddr & ~PAGE_MASK);
@@ -1831,7 +1828,7 @@ void sh_emulate_unmap_dest(struct vcpu *
* - it was aligned to the PTE boundaries; and
* - _PAGE_PRESENT was clear before and after the write.
*/
- shflags = mfn_to_page(sh_ctxt->mfn1)->shadow_flags;
+ shflags = mfn_to_page(sh_ctxt->mfn[0])->shadow_flags;
#if (SHADOW_OPTIMIZATIONS & SHOPT_SKIP_VERIFY)
if ( sh_ctxt->low_bit_was_clear
&& !(*(u8 *)addr & _PAGE_PRESENT)
@@ -1852,12 +1849,12 @@ void sh_emulate_unmap_dest(struct vcpu *
&& bytes <= 4)) )
{
/* Writes with this alignment constraint can't possibly cross pages. */
- ASSERT(!mfn_valid(sh_ctxt->mfn2));
+ ASSERT(!mfn_valid(sh_ctxt->mfn[1]));
}
else
#endif /* SHADOW_OPTIMIZATIONS & SHOPT_SKIP_VERIFY */
{
- if ( unlikely(mfn_valid(sh_ctxt->mfn2)) )
+ if ( unlikely(mfn_valid(sh_ctxt->mfn[1])) )
{
/* Validate as two writes, one to each page. */
b1 = PAGE_SIZE - (((unsigned long)addr) & ~PAGE_MASK);
@@ -1865,16 +1862,16 @@ void sh_emulate_unmap_dest(struct vcpu *
ASSERT(b2 < bytes);
}
if ( likely(b1 > 0) )
- sh_validate_guest_pt_write(v, sh_ctxt->mfn1, addr, b1);
+ sh_validate_guest_pt_write(v, sh_ctxt->mfn[0], addr, b1);
if ( unlikely(b2 > 0) )
- sh_validate_guest_pt_write(v, sh_ctxt->mfn2, addr + b1, b2);
+ sh_validate_guest_pt_write(v, sh_ctxt->mfn[1], addr + b1, b2);
}
- paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn1));
+ paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn[0]));
- if ( unlikely(mfn_valid(sh_ctxt->mfn2)) )
+ if ( unlikely(mfn_valid(sh_ctxt->mfn[1])) )
{
- paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn2));
+ paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn[1]));
vunmap((void *)((unsigned long)addr & PAGE_MASK));
}
else
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -4615,13 +4615,13 @@ static void emulate_unmap_dest(struct vc
u32 bytes,
struct sh_emulate_ctxt *sh_ctxt)
{
- ASSERT(mfn_valid(sh_ctxt->mfn1));
+ ASSERT(mfn_valid(sh_ctxt->mfn[0]));
/* If we are writing lots of PTE-aligned zeros, might want to unshadow */
if ( likely(bytes >= 4) && (*(u32 *)addr == 0) )
{
if ( ((unsigned long) addr & ((sizeof (guest_intpte_t)) - 1)) == 0 )
- check_for_early_unshadow(v, sh_ctxt->mfn1);
+ check_for_early_unshadow(v, sh_ctxt->mfn[0]);
/* Don't reset the heuristic if we're writing zeros at non-aligned
* addresses, otherwise it doesn't catch REP MOVSD on PAE guests */
}
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -727,7 +727,7 @@ struct sh_emulate_ctxt {
struct segment_register seg_reg[6];
/* MFNs being written to in write/cmpxchg callbacks */
- mfn_t mfn1, mfn2;
+ mfn_t mfn[2];
#if (SHADOW_OPTIMIZATIONS & SHOPT_SKIP_VERIFY)
/* Special case for avoiding having to verify writes: remember
[-- Attachment #2: x86-sh-mfn-array.patch --]
[-- Type: text/plain, Size: 6489 bytes --]
x86/shadow: avoid extra local array variable
mfns[2] was there just because struct sh_emulate_ctxt's two MFN values
can't be used to hand to vmap(). Making the structure fields an array
avoids the extra copying.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -1746,11 +1746,11 @@ void *sh_emulate_map_dest(struct vcpu *v
struct domain *d = v->domain;
void *map;
- sh_ctxt->mfn1 = emulate_gva_to_mfn(v, vaddr, sh_ctxt);
- if ( !mfn_valid(sh_ctxt->mfn1) )
- return ((mfn_x(sh_ctxt->mfn1) == BAD_GVA_TO_GFN) ?
+ sh_ctxt->mfn[0] = emulate_gva_to_mfn(v, vaddr, sh_ctxt);
+ if ( !mfn_valid(sh_ctxt->mfn[0]) )
+ return ((mfn_x(sh_ctxt->mfn[0]) == BAD_GVA_TO_GFN) ?
MAPPING_EXCEPTION :
- (mfn_x(sh_ctxt->mfn1) == READONLY_GFN) ?
+ (mfn_x(sh_ctxt->mfn[0]) == READONLY_GFN) ?
MAPPING_SILENT_FAIL : MAPPING_UNHANDLEABLE);
#ifndef NDEBUG
@@ -1767,39 +1767,36 @@ void *sh_emulate_map_dest(struct vcpu *v
/* Unaligned writes mean probably this isn't a pagetable. */
if ( vaddr & (bytes - 1) )
- sh_remove_shadows(d, sh_ctxt->mfn1, 0, 0 /* Slow, can fail. */ );
+ sh_remove_shadows(d, sh_ctxt->mfn[0], 0, 0 /* Slow, can fail. */ );
if ( likely(((vaddr + bytes - 1) & PAGE_MASK) == (vaddr & PAGE_MASK)) )
{
/* Whole write fits on a single page. */
- sh_ctxt->mfn2 = _mfn(INVALID_MFN);
- map = map_domain_page(sh_ctxt->mfn1) + (vaddr & ~PAGE_MASK);
+ sh_ctxt->mfn[1] = _mfn(INVALID_MFN);
+ map = map_domain_page(sh_ctxt->mfn[0]) + (vaddr & ~PAGE_MASK);
}
- else
+ else if ( !is_hvm_domain(d) )
{
- mfn_t mfns[2];
-
/*
* Cross-page emulated writes are only supported for HVM guests;
* PV guests ought to know better.
*/
- if ( !is_hvm_domain(d) )
- return MAPPING_UNHANDLEABLE;
-
+ return MAPPING_UNHANDLEABLE;
+ }
+ else
+ {
/* This write crosses a page boundary. Translate the second page. */
- sh_ctxt->mfn2 = emulate_gva_to_mfn(v, vaddr + bytes, sh_ctxt);
- if ( !mfn_valid(sh_ctxt->mfn2) )
- return ((mfn_x(sh_ctxt->mfn2) == BAD_GVA_TO_GFN) ?
+ sh_ctxt->mfn[1] = emulate_gva_to_mfn(v, vaddr + bytes, sh_ctxt);
+ if ( !mfn_valid(sh_ctxt->mfn[1]) )
+ return ((mfn_x(sh_ctxt->mfn[1]) == BAD_GVA_TO_GFN) ?
MAPPING_EXCEPTION :
- (mfn_x(sh_ctxt->mfn2) == READONLY_GFN) ?
+ (mfn_x(sh_ctxt->mfn[1]) == READONLY_GFN) ?
MAPPING_SILENT_FAIL : MAPPING_UNHANDLEABLE);
/* Cross-page writes mean probably not a pagetable. */
- sh_remove_shadows(d, sh_ctxt->mfn2, 0, 0 /* Slow, can fail. */ );
+ sh_remove_shadows(d, sh_ctxt->mfn[1], 0, 0 /* Slow, can fail. */ );
- mfns[0] = sh_ctxt->mfn1;
- mfns[1] = sh_ctxt->mfn2;
- map = vmap(mfns, 2);
+ map = vmap(sh_ctxt->mfn, 2);
if ( !map )
return MAPPING_UNHANDLEABLE;
map += (vaddr & ~PAGE_MASK);
@@ -1831,7 +1828,7 @@ void sh_emulate_unmap_dest(struct vcpu *
* - it was aligned to the PTE boundaries; and
* - _PAGE_PRESENT was clear before and after the write.
*/
- shflags = mfn_to_page(sh_ctxt->mfn1)->shadow_flags;
+ shflags = mfn_to_page(sh_ctxt->mfn[0])->shadow_flags;
#if (SHADOW_OPTIMIZATIONS & SHOPT_SKIP_VERIFY)
if ( sh_ctxt->low_bit_was_clear
&& !(*(u8 *)addr & _PAGE_PRESENT)
@@ -1852,12 +1849,12 @@ void sh_emulate_unmap_dest(struct vcpu *
&& bytes <= 4)) )
{
/* Writes with this alignment constraint can't possibly cross pages. */
- ASSERT(!mfn_valid(sh_ctxt->mfn2));
+ ASSERT(!mfn_valid(sh_ctxt->mfn[1]));
}
else
#endif /* SHADOW_OPTIMIZATIONS & SHOPT_SKIP_VERIFY */
{
- if ( unlikely(mfn_valid(sh_ctxt->mfn2)) )
+ if ( unlikely(mfn_valid(sh_ctxt->mfn[1])) )
{
/* Validate as two writes, one to each page. */
b1 = PAGE_SIZE - (((unsigned long)addr) & ~PAGE_MASK);
@@ -1865,16 +1862,16 @@ void sh_emulate_unmap_dest(struct vcpu *
ASSERT(b2 < bytes);
}
if ( likely(b1 > 0) )
- sh_validate_guest_pt_write(v, sh_ctxt->mfn1, addr, b1);
+ sh_validate_guest_pt_write(v, sh_ctxt->mfn[0], addr, b1);
if ( unlikely(b2 > 0) )
- sh_validate_guest_pt_write(v, sh_ctxt->mfn2, addr + b1, b2);
+ sh_validate_guest_pt_write(v, sh_ctxt->mfn[1], addr + b1, b2);
}
- paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn1));
+ paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn[0]));
- if ( unlikely(mfn_valid(sh_ctxt->mfn2)) )
+ if ( unlikely(mfn_valid(sh_ctxt->mfn[1])) )
{
- paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn2));
+ paging_mark_dirty(v->domain, mfn_x(sh_ctxt->mfn[1]));
vunmap((void *)((unsigned long)addr & PAGE_MASK));
}
else
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -4615,13 +4615,13 @@ static void emulate_unmap_dest(struct vc
u32 bytes,
struct sh_emulate_ctxt *sh_ctxt)
{
- ASSERT(mfn_valid(sh_ctxt->mfn1));
+ ASSERT(mfn_valid(sh_ctxt->mfn[0]));
/* If we are writing lots of PTE-aligned zeros, might want to unshadow */
if ( likely(bytes >= 4) && (*(u32 *)addr == 0) )
{
if ( ((unsigned long) addr & ((sizeof (guest_intpte_t)) - 1)) == 0 )
- check_for_early_unshadow(v, sh_ctxt->mfn1);
+ check_for_early_unshadow(v, sh_ctxt->mfn[0]);
/* Don't reset the heuristic if we're writing zeros at non-aligned
* addresses, otherwise it doesn't catch REP MOVSD on PAE guests */
}
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -727,7 +727,7 @@ struct sh_emulate_ctxt {
struct segment_register seg_reg[6];
/* MFNs being written to in write/cmpxchg callbacks */
- mfn_t mfn1, mfn2;
+ mfn_t mfn[2];
#if (SHADOW_OPTIMIZATIONS & SHOPT_SKIP_VERIFY)
/* Special case for avoiding having to verify writes: remember
[-- Attachment #3: Type: text/plain, Size: 126 bytes --]
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next prev parent reply other threads:[~2016-03-10 10:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-10 10:06 [PATCH 0/2] x86/shadow: further code size reduction Jan Beulich
2016-03-10 10:13 ` [PATCH 1/2] x86/shadow: compile most write emulation code just once Jan Beulich
2016-03-10 11:40 ` Andrew Cooper
[not found] ` <20160310121750.GB86157@deinos.phlegethon.org>
2016-03-10 13:13 ` Jan Beulich
2016-03-10 10:13 ` Jan Beulich [this message]
2016-03-10 11:43 ` [PATCH 2/2] x86/shadow: avoid extra local array variable Andrew Cooper
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