[Xen-devel] [PATCH v5 1/6] x86: allow IRQ to be disabled for resource access

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

Add the ability to disable IRQ when operating on certain continuous
resource entries. If one entry is marked as
XEN_RESOURCE_ENTRY_FLAGS_DISABLE_IRQ, then the resource operation on
both the entry and the following entry will be done with IRQ disabled.

Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
---
 tools/libxc/xc_psr.c              |  4 ++--
 xen/arch/x86/platform_hypercall.c | 22 +++++++++++++++++++++-
 xen/include/public/platform.h     |  3 ++-
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/tools/libxc/xc_psr.c b/tools/libxc/xc_psr.c
index 872e6dc..87db3a5 100644
--- a/tools/libxc/xc_psr.c
+++ b/tools/libxc/xc_psr.c
@@ -158,12 +158,12 @@ int xc_psr_cmt_get_data(xc_interface *xch, uint32_t rmid,
     entries[0].u.cmd = XEN_RESOURCE_OP_MSR_WRITE;
     entries[0].idx = MSR_IA32_CMT_EVTSEL;
     entries[0].val = (uint64_t)rmid << 32 | evtid;
-    entries[0].rsvd = 0;
+    entries[0].flags = 0;
 
     entries[1].u.cmd = XEN_RESOURCE_OP_MSR_READ;
     entries[1].idx = MSR_IA32_CMT_CTR;
     entries[1].val = 0;
-    entries[1].rsvd = 0;
+    entries[1].flags = 0;
 
     op.cpu = cpu;
     op.nr_entries = 2;
diff --git a/xen/arch/x86/platform_hypercall.c 
b/xen/arch/x86/platform_hypercall.c
index 32f39b2..df99bad 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -90,7 +90,9 @@ static void check_resource_access(struct xen_resource_access 
*ra)
         int ret = 0;
         xenpf_resource_entry_t *entry = ra->entries + i;
 
-        if ( entry->rsvd )
+        /* DISABLE_IRQ flag should never be set for the last entry */
+        if ( entry->flags & XEN_RESOURCE_ENTRY_FLAGS_DISABLE_IRQ &&
+             i == ra->nr_entries - 1 )
         {
             entry->u.ret = -EINVAL;
             break;
@@ -124,11 +126,19 @@ static void resource_access(void *info)
 {
     struct xen_resource_access *ra = info;
     unsigned int i;
+    unsigned long irqflags = 0;
+    bool_t irq_disabled = 0;
 
     for ( i = 0; i < ra->nr_done; i++ )
     {
         int ret;
         xenpf_resource_entry_t *entry = ra->entries + i;
+        if ( !irq_disabled &&
+             entry->flags & XEN_RESOURCE_ENTRY_FLAGS_DISABLE_IRQ )
+        {
+            irq_disabled = 1;
+            local_irq_save(irqflags);
+        }
 
         switch ( entry->u.cmd )
         {
@@ -143,6 +153,13 @@ static void resource_access(void *info)
             break;
         }
 
+        if ( irq_disabled &&
+             !(entry->flags & XEN_RESOURCE_ENTRY_FLAGS_DISABLE_IRQ) )
+        {
+            local_irq_restore(irqflags);
+            irq_disabled = 0;
+        }
+
         if ( ret )
         {
             entry->u.ret = ret;
@@ -150,6 +167,9 @@ static void resource_access(void *info)
         }
     }
 
+    if ( irq_disabled )
+        local_irq_restore(irqflags);
+
     ra->nr_done = i;
 }
 
diff --git a/xen/include/public/platform.h b/xen/include/public/platform.h
index 5c57615..ef30ac2 100644
--- a/xen/include/public/platform.h
+++ b/xen/include/public/platform.h
@@ -545,7 +545,8 @@ struct xenpf_resource_entry {
         uint32_t cmd;   /* IN: XEN_RESOURCE_OP_* */
         int32_t  ret;   /* OUT: return value for failed entry */
     } u;
-    uint32_t rsvd;      /* IN: padding and must be zero */
+#define XEN_RESOURCE_ENTRY_FLAGS_DISABLE_IRQ  1
+    uint32_t flags;     /* IN: XEN_RESOURCE_ENTRY_FLAGS_* */
     uint64_t idx;       /* IN: resource address to access */
     uint64_t val;       /* IN/OUT: resource value to set/get */
 };
-- 
1.9.1


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