[Xen-changelog] [xen master] x86/HVM: extend LAPIC shortcuts around P2M lookups

[patchbot@xxxxxxx]

commit fd1863847af15c3676348447755e1a1801f9d394
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Aug 4 13:46:03 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Aug 4 13:46:03 2014 +0200

    x86/HVM: extend LAPIC shortcuts around P2M lookups
    
    ... to all internally handled MMIO regions. It is in particular the
    HPET page that, e.g. on Windows Server 2012 R2, can get heavily
    accessed, and hence avoiding the unnecessary lookups is rather
    beneficial (in the reported case a 40+-vCPU guest would previously not
    have booted at all while with hvm_hap_nested_page_fault() shortcut
    alone it was able to boot up in 18 minutes [i.e. still room for
    improvement]).
    
    Note the apparently unrelated addition of a is_hvm_vcpu() check to the
    __hvm_copy() code: Afaict for PVH this shortcut should never have taken
    effect (since there's no LAPIC in that case).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Tim Deegan <tim@xxxxxxx>
---
 xen/arch/x86/hvm/hvm.c       |   25 ++++++++++++++++++-------
 xen/arch/x86/hvm/intercept.c |   12 ++++++++++++
 xen/include/asm-x86/hvm/io.h |    1 +
 3 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index e834406..31629e7 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2779,11 +2779,14 @@ int hvm_hap_nested_page_fault(paddr_t gpa,
         }
     }
 
-    /* For the benefit of 32-bit WinXP (& older Windows) on AMD CPUs,
-     * a fast path for LAPIC accesses, skipping the p2m lookup. */
+    /*
+     * No need to do the P2M lookup for internally handled MMIO, benefiting
+     * - 32-bit WinXP (& older Windows) on AMD CPUs for LAPIC accesses,
+     * - newer Windows (like Server 2012) for HPET accesses.
+     */
     if ( !nestedhvm_vcpu_in_guestmode(v)
          && is_hvm_vcpu(v)
-         && gfn == PFN_DOWN(vlapic_base_address(vcpu_vlapic(v))) )
+         && hvm_mmio_internal(gpa) )
     {
         if ( !handle_mmio() )
             hvm_inject_hw_exception(TRAP_gp_fault, 0);
@@ -3892,7 +3895,9 @@ static enum hvm_copy_result __hvm_copy(
 
     while ( todo > 0 )
     {
-        count = min_t(int, PAGE_SIZE - (addr & ~PAGE_MASK), todo);
+        paddr_t gpa = addr & ~PAGE_MASK;
+
+        count = min_t(int, PAGE_SIZE - gpa, todo);
 
         if ( flags & HVMCOPY_virt )
         {
@@ -3907,16 +3912,22 @@ static enum hvm_copy_result __hvm_copy(
                     hvm_inject_page_fault(pfec, addr);
                 return HVMCOPY_bad_gva_to_gfn;
             }
+            gpa |= (paddr_t)gfn << PAGE_SHIFT;
         }
         else
         {
             gfn = addr >> PAGE_SHIFT;
+            gpa = addr;
         }
 
-        /* For the benefit of 32-bit WinXP (& older Windows) on AMD CPUs,
-         * a fast path for LAPIC accesses, skipping the p2m lookup. */
+        /*
+         * No need to do the P2M lookup for internally handled MMIO, benefiting
+         * - 32-bit WinXP (& older Windows) on AMD CPUs for LAPIC accesses,
+         * - newer Windows (like Server 2012) for HPET accesses.
+         */
         if ( !nestedhvm_vcpu_in_guestmode(curr)
-             && gfn == PFN_DOWN(vlapic_base_address(vcpu_vlapic(curr))) )
+             && is_hvm_vcpu(curr)
+             && hvm_mmio_internal(gpa) )
             return HVMCOPY_bad_gfn_to_mfn;
 
         page = get_page_from_gfn(curr->domain, gfn, &p2mt, P2M_UNSHARE);
diff --git a/xen/arch/x86/hvm/intercept.c b/xen/arch/x86/hvm/intercept.c
index 7cc13b5..797eedf 100644
--- a/xen/arch/x86/hvm/intercept.c
+++ b/xen/arch/x86/hvm/intercept.c
@@ -163,6 +163,18 @@ static int hvm_mmio_access(struct vcpu *v,
     return rc;
 }
 
+bool_t hvm_mmio_internal(paddr_t gpa)
+{
+    struct vcpu *curr = current;
+    unsigned int i;
+
+    for ( i = 0; i < HVM_MMIO_HANDLER_NR; ++i )
+        if ( hvm_mmio_handlers[i]->check_handler(curr, gpa) )
+            return 1;
+
+    return 0;
+}
+
 int hvm_mmio_intercept(ioreq_t *p)
 {
     struct vcpu *v = current;
diff --git a/xen/include/asm-x86/hvm/io.h b/xen/include/asm-x86/hvm/io.h
index 8228ab8..c7ac566 100644
--- a/xen/include/asm-x86/hvm/io.h
+++ b/xen/include/asm-x86/hvm/io.h
@@ -91,6 +91,7 @@ static inline int hvm_buffered_io_intercept(ioreq_t *p)
     return hvm_io_intercept(p, HVM_BUFFERED_IO);
 }
 
+bool_t hvm_mmio_internal(paddr_t gpa);
 int hvm_mmio_intercept(ioreq_t *p);
 int hvm_buffered_io_send(ioreq_t *p);
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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