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On Mon, Apr 10, 2017 at 3:44 AM, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> wrote:

This patch adds support for testing instruction emulation when
required by the vm_event reply sent for MEM_ACCESS events. To this
end, it adds the "emulate_write" and "emulate_exec" parameters
that behave like the old "write" and "exec" parameters, except
instead of allowing writes / executes for a hit page, they emulate
the trigger instruction. The new parameters don't mark all of the
guest's pages, instead they stop at the arbitrary low limit of
the first 1000 pages - otherwise the guest would slow to a crawl.
Since the emulator is still incomplete and has trouble with
emulating competing writes in SMP scenarios, the new tests are
only meant for debugging issues.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
tools/tests/xen-access/xen-access.c | 38 ++++++++++++++++++++++++++++---------
1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/tools/tests/xen-access/xen-access.c b/tools/tests/xen-access/xen-access.c
index ff4d289..0ba2e45 100644
--- a/tools/tests/xen-access/xen-access.c
+++ b/tools/tests/xen-access/xen-access.c
@@ -335,7 +335,7 @@ static void put_response(vm_event_t *vm_event, vm_event_response_t *rsp)

void usage(char* progname)
{
- fprintf(stderr, "Usage: %s [-m] <domain_id> write|exec", progname);
+ fprintf(stderr, "Usage: %s [-m] <domain_id> write|exec|emulate_write|emulate_exec", progname);

These options are only for x86, so they need to be moved into the #if block below.

#if defined(__i386__) || defined(__x86_64__)
fprintf(stderr, "|breakpoint|altp2m_write|altp2m_exec|debug|cpuid|desc_access");
#elif defined(__arm__) || defined(__aarch64__)
@@ -369,6 +369,7 @@ int main(int argc, char *argv[])
int debug = 0;
int cpuid = 0;
int desc_access = 0;
+ int emulate = 0;
uint16_t altp2m_view_id = 0;

char* progname = argv[0];
@@ -404,12 +405,26 @@ int main(int argc, char *argv[])
after_first_access = XENMEM_access_rwx;
memaccess = 1;
}
+ else if ( !strcmp(argv[0], "emulate_write") )
+ {
+ default_access = XENMEM_access_rx;
+ after_first_access = XENMEM_access_rwx;

Setting after_first_access not needed.

+ emulate = 1;
+ memaccess = 1;
+ }
else if ( !strcmp(argv[0], "exec") )
{
default_access = XENMEM_access_rw;
after_first_access = XENMEM_access_rwx;
memaccess = 1;
}
+ else if ( !strcmp(argv[0], "emulate_exec") )
+ {
+ default_access = XENMEM_access_rw;
+ after_first_access = XENMEM_access_rwx;

Setting after_first_access not needed.

+ emulate = 1;
+ memaccess = 1;
+ }
#if defined(__i386__) || defined(__x86_64__)
else if ( !strcmp(argv[0], "breakpoint") )
{
@@ -536,7 +551,7 @@ int main(int argc, char *argv[])
}

rc = xc_set_mem_access(xch, domain_id, default_access, START_PFN,
- (xenaccess->max_gpfn - START_PFN) );
+ emulate ? 1000 : (xenaccess->max_gpfn - START_PFN));

Why only 1000? What if the domain has less then 1000?

if ( rc < 0 )
{
@@ -702,15 +717,20 @@ int main(int argc, char *argv[])
}
else if ( default_access != after_first_access )
{
- rc = xc_set_mem_access(xch, domain_id, after_first_access,
- req.u.mem_access.gfn, 1);
- if (rc < 0)
+ if ( !emulate )
{
- ERROR("Error %d setting gfn to access_type %d\n", rc,
- after_first_access);
- interrupted = -1;
- continue;
+ rc = xc_set_mem_access(xch, domain_id, after_first_access,
+ req.u.mem_access.gfn, 1);
+ if (rc < 0)
+ {
+ ERROR("Error %d setting gfn to access_type %d\n", rc,
+ after_first_access);
+ interrupted = -1;
+ continue;
+ }
}
+ else
+ rsp.flags |= VM_EVENT_FLAG_EMULATE;
}

rsp.u.mem_access = req.u.mem_access;
--
1.9.1

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Re: [Xen-devel] [PATCH] tests/xen-access: Added vm_event emulation tests